Narrowly prevent etcd from crashing when given a bad ACTIVATE payload, e.g.:
$ curl -d "{\"action\":\"ACTIVATE\"}" ${ETCD}/v3/maintenance/alarm
curl: (52) Empty reply from server
Thanks to this change:
- all the maps bucket -> buffer are indexed by int's instead of
string. No need to do: byte[] -> string -> hash conversion on each
access.
- buckets are strongly typed in backend/mvcc API.
During review of: https://github.com/etcd-io/etcd/pull/12988 spotted
that PUT is actially writing to v3-backend.
If we are replaying WAL log, it might happened that backend's
applied_index is > than the WAL's log entry. In such situation we should
skip applying on backend V3.
I think both the methods (setVersion, setMembersAttributes) are in
practice idempotent so its not that 'serious' problem, but for
formal correctness adding the proper checks.
Motivation is as follows:
- etcdctl we only depend on clientv3 APIs, no dependencies of bolt, backend, mvcc, file-layout
- etcdctl can be officially supported across wide range of versions, while etcdutl is pretty specific to file format at particular version.
it's step towards desired modules layout, documented in: https://etcd.io/docs/next/dev-internal/modules/
Seems that additinal refresh of go.sum files is needed during the
release process after editing the versions of modules.
Discovered the problem while I was testing whether etcdutl is
properly included in the target binaries using:
```
DRY_RUN=true REPOSITORY=\`pwd\` BRANCH='branch-with-etcdutl' ./scripts/release 3.5.0-foobar.2
```
2 problems:
- spawnCmdWithLogger was not implemented (when built with 'cov' tag)
- the logic was depending on relative paths. We change it to absolute
to be able to run in the test-specific temporary directories.
- Moves grpcproxy & functional tests to a separate workflows such thay can get restarted independently.
- Configures travis to run 1.16.3 go version (as travis cannot resolve 1.16 to the default).
This makes (bbolt) backend a full feature snapshot in term of WAL/raft,
i.e. carries:
- commit : (applied_index)
- confState
Benefits:
- Backend will be a sufficient point in time definition sufficient to
start replaying WAL. We have applied_index & confState in consistent
state.
- In case of emergency a backend state can be used for recovery
Flags `--experimental-enable-v2v3` and '-enable-v2' will raise a warning in 3.5,
in 3.6 they are schedule for decomissioning, such that v2store can stop be written in 3.7.
Deprecation plan in: https://github.com/etcd-io/etcd/issues/12913
Every transaction committed to backend is writing most recent consistent_index.
Makes sure that even automatically trigger commits of batch-transactions
stays "really" consistent a.d. the most recent WAL log index applied.
clientv3 logs (especially tests) were poluted with unattributed to testing.T log lines:
```
{"level":"warn","ts":"2021-04-29T12:42:11.055+0200","logger":"etcd-client","caller":"v3/retry_interceptor.go:64","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc0000fafc0/#initially=[unix://localhost:m10]","attempt":0,"error":"rpc error: code = ResourceExhausted desc = etcdserver: mvcc: database space exceeded"}
```
The reasons were 2 fold:
- Interceptors were copying logger before "WithLogger" could modify it.
- We were not propagating the loggers in a few testing contexts.
Prior to this CL, `ETCDCTL_API=2 etcdctl backup --with-v3` was readacting WAL log
(by removal of some entries), but was NOT updating consistent_index in the backend.
Also the WAL editing logic was buggy, as it didn't took in consideration the fact
that when TERM changes, there can be entries with duplicated indexes in
the log. So its NOT sufficient to subtract number of removed entries to
get accurate log indexes.
The PR replaces removing and shifting of WAL entries with replacing them with an no-op entries.
Thanks to this consistent-index references are staying up to date.
The PR also:
- updates 'verification' logic to check whether consistent_index does not lag befor last snapshot
- env-gated execution of verification framework in `etcdctl backup`.
Tested with:
```
(./build.sh && cd tests && EXPECT_DEBUG=TRUE 'env' 'go' 'test' '-timeout=300m' 'go.etcd.io/etcd/tests/v3/e2e' -run=TestCtlV2Backup --count=1000 2>&1 | tee TestCtlV2BackupV3.log)
```
correct 'backend' (bbolt) context in aspect of membership.
Prior to this change the 'restored' backend used to still contain:
- old memberid (mvcc deletion used, why the membership is in bolt
bucket, but not mvcc part):
```
mvs := mvcc.NewStore(s.lg, be, lessor, ci, mvcc.StoreConfig{CompactionBatchLimit: math.MaxInt32})
defer mvs.Close()
txn := mvs.Write(traceutil.TODO())
btx := be.BatchTx()
del := func(k, v []byte) error {
txn.DeleteRange(k, nil)
return nil
}
// delete stored members from old cluster since using new members
btx.UnsafeForEach([]byte("members"), del)
```
- didn't get new members added.
Infrequently the test flaked. Reproducable with:
```
go test go.etcd.io/etcd/tests/v3/integration --run TestFirstCommitNotification --count=500
```
The moveLeader finishes when configchange is commited by quorum.
It doesn't guarantee that the 'empty' record was committed by the new leader.
From time to time happened that appliedLeaderIndex was returning 9
(without empty entry) and the test flaked. In healthy case the
appliedIndex returned 10.
Fixed by putting kv pair after leader change. The pair is guaranteed
to be stored on index when put finishes (so the empty entry as well).
So far each instance of embed server was overriding the grpc loggers and zap.global loggers.
It's counter intutitive that last created Embedded server was 'wining' and more-over it was breaking grpc expectation to change it "only" before the grpc stack is being used.
This PR introduces explicit call: `embed.Config::SetupGlobalLoggers()`, that changes the loggers where requested. The call is used by etcd main binary.
The immediate benefit from this change is reduction of test flakiness, as there were flakes due to not a proper logger being used across tests.
ClusterVersionSet, ClusterMemberAttrSet, DowngradeInfoSet functions are
writing both to V2store and backend. Prior this CL there were
in a branch not executed if shouldApplyV3 was false,
e.g. during restore when Backend is up-to-date (has high
consistency-index) while v2store requires replay from WAL log.
The most serious consequence of this bug was that v2store after restore
could have different index (revision) than the same exact store before restore,
so potentially different content between replicas.
Also this change is supressing double-applying of Membership
(ClusterConfig) changes on Backend (store v3) - that lackilly are not
part of MVCC/KeyValue store, so they didn't caused Revisions to be
bumped.
Inspired by jingyih@ comment:
https://github.com/etcd-io/etcd/pull/12820#issuecomment-815299406
While it appears that etcd is not vulnerable to CVE-2021-3121,
it is a good idea to update to the new generator so that new
vulnerable code isn't generated in any future APIs. Also, this
lays the issue to rest of whether there is any issue with
etcd and CVE-2021-3121.
This commit removes the `XXX_NoUnkeyedLiteral`, `XXX_unrecognized`, and
`XXX_sizecache` auto-generated fields from generated protobuf structs in
the raft package. This was done for all of the same reasons CockroachDB
removed the generation of these fields in https://github.com/cockroachdb/cockroach/pull/38404.
They come with very limited advantages but moderate disadvantages.
`XXX_NoUnkeyedLiteral` and `XXX_sizecache` were only enabled recently in
cc7b4fa, and this appears to have been unintentional. Meanwhile,
`XXX_unrecognized` has been around for longer and has arguably more
reason to stay because it can assist with forwards compatibility.
However, any real mixed-version upgrade story for this package is mostly
untold at this point, and keeping this field seems just as likely to
cause unexpected bugs (e.g. a field was propagated but not updated
correctly when passed through an old version) as it seems to fix real
issues, so it also doesn't warrant its cost.
This reduces the in-memory representation size of all Raft protos.
Notably, it reduces the memory size of an `Entry` proto from *80 bytes*
to *48 bytes* and the memory size of a `Message` proto from *392 bytes*
to *264 bytes*. Both of these structs are used frequently, and often in
slices, where this wasted space really starts to add up.
This was motivated by a regression in microbenchmarks in CockroachDB due
to cc7b4fa, which was caught in https://github.com/cockroachdb/cockroach/issues/62212.
Motivation:
- ServerConfig is part of 'embed' public API, while etcdserver is more 'internal'
- EtcdServer is already too big and config is pretty wide-spread leaf
if we were to split etcdserver (e.g. into pre & post-apply part).
Thanks to this, unix sockets should be not longer
created by integration tests in the the source code directory,
so potentially trigger IDE reloads and unnecessery load (and mess).
Thanks to this the logs:
- are automatically printed if the test fails.
- are in pretty consistent format.
- are annotated by 'member' information of the cluster emitting them.
Side changes:
- Set propert default got DefaultWarningApplyDuration (used to be '0')
- Name the members based on their 'place' on the list (as opposed to
'random')
The flag protects etcd memory from being swapped out to disk.
This can happen in memory constrained systems where mmaped bbolt
area is natural condidate for swapping out.
This flag should provide better tail latency on the cost of higher RSS
ram usage. If the experiment is successful, the logic should get moved
into bbolt layer, where we can protect specific bbolt instances
(e.g. avoid protecting both during defragmentation).
There are situations where we don't wish to fsync but we do want to
write the data.
Typically this occurs in clusters where fsync latency (often the
result of firmware) transiently spikes. For Kubernetes clusters this
causes (many) elections which have knock-on effects such that the API
server will transiently fail causing other components fail in turn.
By writing the data (buffered and asynchronously flushed, so in most
situations the write is fast) and avoiding the fsync we no longer
trigger this situation and opportunistically write out the data.
Anecdotally:
Because the fsync is missing there is the argument that certain
types of failure events will cause data corruption or loss, in
testing this wasn't seen. If this was to occur the expectation is
the member can be readded to a cluster or worst-case restored from a
robust persisted snapshot.
The etcd members are deployed across isolated racks with different
power feeds. An instantaneous failure of all of them simultaneously
is unlikely.
Testing was usually of the form:
* create (Kubernetes) etcd write-churn by creating replicasets of
some 1000s of pods
* break/fail the leader
Failure testing included:
* hard node power-off events
* disk removal
* orderly reboots/shutdown
In all cases when the node recovered it was able to rejoin the
cluster and synchronize.
The purpose of this change is to learn more about flake cases like:
https://travis-ci.com/github/etcd-io/etcd/jobs/488324449
```
% (cd tests && 'env' 'go' 'test' '-timeout=30m' '--race=false' '--cpu=2' './integration/...')
stderr: go: downloading github.com/golang/groupcache v0.0.0-20200121045136-8c9f03a8e57e
ok go.etcd.io/etcd/tests/v3/integration 197.295s
ok go.etcd.io/etcd/tests/v3/integration/client 0.089s
ok go.etcd.io/etcd/tests/v3/integration/client/examples 0.038s
ok go.etcd.io/etcd/tests/v3/integration/clientv3 70.365s
ok go.etcd.io/etcd/tests/v3/integration/clientv3/concurrency 3.169s
ok go.etcd.io/etcd/tests/v3/integration/clientv3/connectivity 100.535s
ok go.etcd.io/etcd/tests/v3/integration/clientv3/examples 1.341s
ok go.etcd.io/etcd/tests/v3/integration/clientv3/experimental/recipes 3.277s
No output has been received in the last 10m0s,
```
We found wait lock contention when a large amount of write operations. Converting wait from single element to an array helps to improve the performance.
Fixes#12731
Signed-off-by: Wilson Wang <wilsonny371@gmail.com>
Seems old versions of https://github.com/certifi/gocertifi where
categorized as "Do What The F*ck You Want To Public License".
Update to newer version that is explicit `Mozilla Public License` 2.0 (MPL 2.0).
If the simpleHTTPClient.Do is called and the context has a nil request, return an error early.
Fixes#12718
Signed-off-by: David Lanouette <David.Lanouette@GMail.com>
In some environments, the CA is not able to sign certificates with both
'client auth' and 'server auth' extended usage parameters and so an operator
needs to be able to set a seperate client certificate to use when making
requests which is different to the certificate used for accepting requests.
This applies to both proxy and etcd member mode and is available as both a CLI
flag and config file field for peer TLS.
Signed-off-by: Ben Meier <ben.meier@oracle.com>
- Fix script that creates manifest-list based multi-arch-images.
The images need to be pushed first.
- Use docker instead of gcloud docker helper
- Make sure docker pushes are properly 'dry run'
- Added preparation instruction to the release script.
- Add a large detailed comment about the use and necessity of
both the follower and leader probing optimization
- fix the log message in stepLeader that previously mixed up the
log term for the rejection and the index of the append
- improve the test via subtests
- add some verbiage in findConflictByTerm around first index
This commit creates a new probe_and_replicate.txt interactive test. The
test creates a complete Raft log configuration and demonstrates how a
leader probes and replicates to each of its followers. The log
configuration constructed is identical to the one present in Figure 7 of
the raft paper (https://raft.github.io/raft.pdf), which looks like:
```
1 2 3 4 5 6 7 8 9 10 11 12
n1: [1][1][1][4][4][5][5][6][6][6]
n2: [1][1][1][4][4][5][5][6][6]
n3: [1][1][1][4]
n4: [1][1][1][4][4][5][5][6][6][6][6]
n5: [1][1][1][4][4][5][5][6][7][7][7][7]
n6: [1][1][1][4][4][4][4]
n7: [1][1][1][2][2][2][3][3][3][3][3]
```
Once in this state, we then elect node 1 as the leader and stabilize the
entire raft group. This demonstrates how a newly elected leader probes
for matching indexes, overwrites conflicting entries, and catches up all
followers.
This will be useful to demonstrate the impact of more efficient probing
behavior.
When we have an external component that checks /health periodically, the
etcd server logs can be quite verbose (e.g., DDOS-ing against insure
etcd health check can lead to disk space full due to large log files).
This change was introduced in #11704.
While we keep the warning logs for etcd health check failures, the
success (or OK) log level should be set to DEBUG.
Fixes#12676
* If there is a snapshot, HTTP server won't start.
* Resotring form snapshot occurs after replaying WAL.
* When taking a snapshot, the last change is not applied to the state machine yet.
1) Fix the path for rpc errors
2) The README says 2 types of client errors vs doc mentioning 3
types of client errors. grpc erros should be considered single time
as covered in the README.
% (cd tests && go vet ./...)
stderr: # go.etcd.io/etcd/tests/v3/integration/clientv3/concurrency_test
stderr: integration/clientv3/concurrency/election_test.go:74:6: call to (*T).Fatal from a non-test goroutine
stderr: integration/clientv3/concurrency/mutex_test.go:57:4: call to (*T).Fatal from a non-test goroutine
Prior to this PR, the e2e tests where creating dirs like:
```
/tmp/testname1.etcd030299846
/tmp/testname0.etcd039445123
/tmp/testname0.etcd206372065
```
and not cleaning them, that led to disk-space-exceeded flakes.
After the PR, the testing.TB tempdir mechanism is used and the names are
being cleaned and are more miningful:
```
../../bin/etcd --name test-TestCtlV3EndpointHashKV-2 --listen-client-urls http://localhost:20010 --advertise-client-urls http://localhost:20010 --listen-peer-urls https://localhost:20011 --initial-advertise-peer-urls https://localhost:20011 --initial-cluster-token new --data-dir /tmp/TestCtlV3EndpointHashKV429176179/003 --snapshot-count 100000 --experimental-initial-corrupt-check --peer-auto-tls --initial-cluster test-TestCtlV3EndpointHashKV-0=https://localhost:20001,test-TestCtlV3EndpointHashKV-1=https://localhost:20006,test-TestCtlV3EndpointHashKV-2=https://localhost:20011
```
This is not yet implementation, just API and tests to be filled
with implementation in next CLs,
tracked by: https://github.com/etcd-io/etcd/issues/12652
We propose here 3 packages:
- clientv3/naming/endpoints ->
That is abstraction layer over etcd that allows to write, read &
watch Endpoints information. It's independent from GRPC API. It hides
the storage details.
- clientv3/naming/endpoints/internal ->
That contains the grpc's compatible Update class to preserve the
internal JSON mashalling format.
- clientv3/naming/resolver ->
That implements the GRPC resolver API, such that etcd can be
used for connection.Dial in grpc.
Please see the grpc_naming.md document changes & grpcproxy/cluster.go
new integration, to see how the new abstractions work.
They used to take >10min with coverage, so were causing interrupted
Travis runs.
Know thay fit in 100-150s (together), thanks also to parallel
execution.
- making sure the DRY_RUN mode can finish e2e, so e.g. commits to
local copy of repository are OK in dry-run (while git pushes are NOT).
- better interaction with ./test_lib.sh script.
- more consistent logging
- bringing back s390x architecture that on go 1.14.3 seems to work as
expected.
Change amd64 docker image to use a `-amd64` suffix, consistent with
other architectures. Introduce a multiarch docker manifest list with
the original (no-arch) docker tag.
Fixes#10380
Changes:
- signing tags.
- allows to override BRANCH and REPOSITORY using env variables.
Tested by a release in my private fork:
BRANCH="20201126-ptabor-release" REPOSITORY="git@github.com:ptabor/etcd.git" ./scripts/release 3.5.0-alpha.20
Both have shown great initiatives and dedication to the project's long-term health and community engagement.
I strongly support for their recognition and continued work on the project.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
- build & test scripts deprecated. Call *.sh variants.
This will avoid delete the symlinks and get rid of
subtle dependency on 'sed --follow-symlinks' on OsX/BSD sed.
- Fix parameters to mktemp
Example:
https://travis-ci.com/github/etcd-io/etcd/jobs/470404938
```
% (cd server && go vet ./...)
stderr: # go.etcd.io/etcd/server/v3/etcdserver/api/v2store
stderr: etcdserver/api/v2store/node_extern_test.go:107:9: possible misuse of reflect.SliceHeader
stderr: etcdserver/api/v2store/node_extern_test.go:107:16: possible misuse of reflect.SliceHeader
```
The root reason of flakes, was that server was considered as ready to
early.
In particular:
```
../../bin/etcd-2456648: {"level":"info","ts":"2021-01-11T09:56:44.474+0100","caller":"rafthttp/stream.go:274","msg":"established TCP streaming connection with remote peer","stream-writer-type":"stream Message","local-member-id":"ed5f620d34a8e61b","remote-peer-id":"ca50e9357181d758"}
../../bin/etcd-2456648: {"level":"warn","ts":"2021-01-11T09:56:49.040+0100","caller":"etcdserver/server.go:1942","msg":"failed to publish local member to cluster through raft","local-member-id":"ed5f620d34a8e61b","local-member-attributes":"{Name:infra2 ClientURLs:[http://localhost:20030]}","request-path":"/0/members/ed5f620d34a8e61b/attributes","publish-timeout":"7s","error":"etcdserver: request timed out, possibly due to connection lost"}
../../bin/etcd-2456648: {"level":"info","ts":"2021-01-11T09:56:49.049+0100","caller":"etcdserver/server.go:1921","msg":"published local member to cluster through raft","local-member-id":"ed5f620d34a8e61b","local-member-attributes":"{Name:infra2 ClientURLs:[http://localhost:20030]}","request-path":"/0/members/ed5f620d34a8e61b/attributes","cluster-id":"34f27e83b3bc2ff","publish-timeout":"7s"}
```
was taking 5s. If this was happening concurrently with etcdctl, the
etcdctl could timeout.
The fix, requires servers to report 'ready to serve client requests' to consider them up.
Fixed also some whitelisted 'goroutines'.
The commit ensures that spawned etcdctl processes are "closed",
so they perform proper os wait processing.
This might have contributed to file-descriptor/open-files limit being
exceeded.
Before:
```
{"level":"info","ts":1610273495.3791487,"caller":"agent/handler.go:668","msg":"cleaning up page cache"}
{"level":"info","ts":1610273495.3793094,"caller":"agent/handler.go:94","msg":"created etcd log file","path":"/tmp/etcd-functional-2/etcd.log"}
{"level":"info","ts":1610273495.379328,"caller":"agent/handler.go:668","msg":"cleaning up page cache"}
[sudo] password for ptab:
pam_glogin: invalid password
Sorry, try again.
[sudo] password for ptab:
```
Now the caches are dropped if the current users is in sudoers, bot not
in the other cases.
To be honest I don't see the purpose for dropping the caches at all in
the test.
Old etcdserver which have not apply pr of #12165 will check auth token
even if the request is an Authenticate request.
If the client has a invalid auth token, it will not able to update it's
token, since the Authenticate has a invalid auth token.
This fix clear the auth token when encounter an ErrInvalidAuthToken to
talk with old version etcd servers.
Fix#12385 with #12165 and #12264
and v3election updated
Current path for v3lock and v3election are set to :
etcdserver/api/v3lock/v3lockpb... and etcdserver/api/v3election/v3electionpb... respectively
changed them to server/etcdserver...
In these unit tests, goroutines may leak if certain branches are chosen. This commit edits channel operations and buffer sizes, so no matter what branch is chosen, the test will end correctly. This commit doesn't change the semantics of unit tests.
Because of the well-known range loop closure issue, the value of u may
have changed by the time the anonymous function mentioned in the defer
is run. To address this, the simplest fix is to pass the url used in the
loop as an argument to the function run in defer.
Before this patch, a client which cancels the context for a watch results in the
server generating a `rpctypes.ErrGRPCNoLeader` error that leads the recording of
a gRPC `Unavailable` metric in association with the client watch cancellation.
The metric looks like this:
grpc_server_handled_total{grpc_code="Unavailable",grpc_method="Watch",grpc_service="etcdserverpb.Watch",grpc_type="bidi_stream"}
So, the watch server has misidentified the error as a server error and then
propagates the mistake to metrics, leading to a false indicator that the leader
has been lost. This false signal then leads to false alerting.
The commit 9c103dd0de introduced an interceptor which wraps
watch streams requiring a leader, causing those streams to be actively canceled
when leader loss is detected.
However, the error handling code assumes all stream context cancellations are
from the interceptor. This assumption is broken when the context was canceled
because of a client stream cancelation.
The core challenge is lack of information conveyed via `context.Context` which
is shared by both the send and receive sides of the stream handling and is
subject to cancellation by all paths (including the gRPC library itself). If any
piece of the system cancels the shared context, there's no way for a context
consumer to understand who cancelled the context or why.
To solve the ambiguity of the stream interceptor code specifically, this patch
introduces a custom context struct which the interceptor uses to expose a custom
error through the context when the interceptor decides to actively cancel a
stream. Now the consuming side can more safely assume a generic context
cancellation can be propagated as a cancellation, and the server generated
leader error is preserved and propagated normally without any special inference.
When a client cancels the stream, there remains a race in the error handling
code between the send and receive goroutines whereby the underlying gRPC error
is lost in the case where the send path returns and is handled first, but this
issue can be taken separately as no matter which paths wins, we can detect a
generic cancellation.
This is a replacement of https://github.com/etcd-io/etcd/pull/11375.
Fixes#10289, #9725, #9576, #9166
instead of v3.0.0-000101010000000-00000000000,
that might be misleading as we don't develop etcd v3.0.0 any longer.
This version is a virtual version and is not supposed to be tagged
within the repository. We should tag real versions like: 3.5.0-alpha.0.
Please notice that go.etcd.io/etcd/client/v2 will be versioned as `v2.305.0-pre`.
The reason is that client v2 must have v2 version. I propose a
convention to envode the major version as 100x in minor version to make
the association to the underlying repository clear, staying within v2
version family.
The change was generated using:
```
DRY_RUN=false TARGET_VERSION="v3.5.0-pre" ./scripts/release_mod.sh update_versions
```
Examplar invocations:
Edit go.mod files such that all etcd modules are pointing on given version:
```
% DRY_RUN=false TARGET_VERSION="v3.5.13" ./scripts/release_mod.sh update_versions
```
Tag latest commit with current version number for all the modules and push upstream:
```
% DRY_RUN=true REMOTE_REPO="origin" ./scripts/release_mod.sh push_mod_tags
```
* Turn off checking of format of commit message.
* scripts/fix.sh: Fix fixing whitespaces in *.sh scripts
Aparently there is a difference between:
find ./ -print0 -name *.sh and
find ./ -name *.sh -print0
* etcdserver unit tests: Do not call .Fatalf(...) from not test's goroutine.
Fixes following test failures:
https://travis-ci.com/github/etcd-io/etcd/jobs/425920416
```
% (cd server && go vet ./...)
stderr: # go.etcd.io/etcd/server/v3/etcdserver
stderr: etcdserver/server_test.go:1002:4: call to (*T).Fatalf from a non-test goroutine
stderr: etcdserver/server_test.go:1166:4: call to (*T).Fatalf from a non-test goroutine
FAIL: (code:2):
% (cd server && go vet ./...)
FAIL: 'run go vet ./...' checking failed (!=0 return code)
FAIL: 'govet' failed at Tue Nov 3 04:07:47 UTC 2020
```
This fixes etcd being unable to send any message longer than 64 KB as
a notification over the websocket. This was because the older version
of grpc-websocket-proxy was used and WithMaxRespBodyBufferSize option
wasn't set.
Co-authored-by: Vitaliy Filippov <vitalif@yourcmc.ru>
We make v2 client code a module go.etcd.io/etcd/client/v2.
Pretty mechanical change that can be summarized as:
mkdir client/v2
cd client/v2 && git mod init go.etcd.io/etcd/client/v2
git mv client/*.go client/v2/
find -name '*.go' | xargs sed -i --follow-symlinks 's|/v3/client["]|/client/v2\"|g'
+ fixing changelog, bom, go.mod etc.
The e2e tests can be flaky due to various tests mutating shared mutable
fixtures, causing non-deterministic behavior depending on the test set, order,
etc.
For example, `configTLS` is mutated in at least two tests in such a way that the
config is potentially invalidated for any subsequent test running in the same
process (e.g. by setting the `enableV2` field). This particular example caused
a substantial amount of confusion diagnosing the new test introduced for
https://github.com/etcd-io/etcd/pull/12370.
Independent tests should not share mutable state unless deliberately. This patch
refactors the e2e test config fixtures to safeguard against these problems by
replacing the package variables (which cannot easily be made immutable) with
functions that return new instances.
This brings consistency between proto-generation code and actual versions of libraries being used in runtime:
github.com/gogo/protobuf v1.2.1,v1.0.0 -> v1.3.1
github.com/golang/protobuf v1.3.2 -> v1.3.5
github.com/grpc-ecosystem/grpc-gateway v1.9.5,v1.4.1,v1.15.2 -> v1.14.6
google.golang.org/grpc v1.26.0 -> v1.29.1
Moved as far as possible, without bumping on grpc 1.30.0 "naming" decomissioning.
Please also notice that gogo/protobuf is likely to reach EOL: https://github.com/gogo/protobuf/issues/691
Fix test case in tests/e2e/etcd_config_test.go:311, here should
check if it is nil. As the following errors:
--- FAIL: TestGrpcproxyAndCommonName (0.00s)
etcd_config_test.go:304: Unexpected error: fork/exec ../../bin/etcd: no such file or directory
etcd_config_test.go:309: Unexpected error: fork/exec ../../bin/etcd: no such file or directory
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x56bd96]
Replace ./scripts/install_tool.sh with `gobin`, such that we have
consistent handling for all tools needed for build and consistent
versioning within ./tools/mod/go.mod.
Side changes:
- Expose /scripts/fix.sh that fixes formatting and bom across modules
- Expose *.sh variants of scripts like build and ./test (first step
towards replacement).
- Make stderr output of commands explicit and make commands use
different color than callouts.
If we create 000000000-0000000.war failed in war tmp dir(XXX.tmp) and we should
remove the tmp dirs. If create war successfully in tmp dir and it will
be renamed to common dir and remove tmp dir(XXX.tmp) will also be ok.
Co-authored-by: yangweiwei <yangweiwei@cmss.chinamobile.com>
This package depends on raft and is solelly used by etcdserver/raft.go.
So it does not fullfills conditions of:
```
pkg/ is a collection of utility packages used by etcd without being specific to etcd itself. A package belongs here
only if it could possibly be moved out into its own repository in the future.
```
Mechanical execution of:
```
git mv ./pkg/mock/mockserver ./client/pkg/mock
git mv ./pkg/mock/{mockstorage,mockstore,mockwait} ./server/pkg/mock
```
The packages depend on etcd API / protos - so they are NOT etcd-dependencies.
In such situation thay should be placed in 'pkg' folder.
"snapshot" Restore/Status code was the only remaining dependency of client on 'server'
code. The code is solelly used by etcdctl. Long-term the snapshot code
should be migrated to 'etcdadm' style of tool such that we can
distinguish tool solelly depending on networking API vs. tools that
operation on etcd files directly.
We left snapshot.Save() code in clientv3.snapshot package, such that
clients can benefits from automated download&safe to file snapshot
functionality over the wire.
During move of code to 'api' (0aab02e7b5),
I overlooked that the ./build script is setting the version on the 'symbol'.
I added a code to ./build script that checks whether the symbol's are in sync.
The raft.status expvar is added at init time.
This change ensures that evaluating that expvar variable
doesn't panic during evaluation, even when there is
no server running.
* namespace: check IsWithFromKey if keyLen equal 0.
Rename function isWithFromKey/isWithPrefix to IsOptsWithFromKey/IsOptsWithPrefix.
fixes: #12282
* integration: add test while WithFromKey/WithPrefix called in opts.
Refactoring script/genproto.sh around state-of-the-art techniques of
managing tooling in go:
- https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module
- uses https://github.com/myitcv/gobin instead of customly created gopath.proto dir
- caches tools between executions
- guaratees hermetics runs (it was not guaranteed for protoc_grpc_gateway that used latest)
The change is no-op for the generated code.
The commit reveals a few 'worring things':
1 We depend on : github.com/grpc-ecosystem/grpc-gateway/@v/v1.4.1/protoc-gen-grpc-gateway
2. And also : github.com/grpc-ecosystem/grpc-gateway/@v/v1.15.0/protoc-gen-swagger/protoc-gen-swagger
3. And on extremely old: github.com/gogo/protobuf@v1.0.0 protoc-gen-gofast that is out of sync with the library linked to binaries: github.com/gogo/protobuf@v1.2.1
We introduce a LazyCluster abstraction (instead of copy-pasted logic)
that makes clusters to be created only if there are runnable tests
in need for the infrastructure.
This CL tries to connect 2 objectives:
- Examples should be close (the same package) to the original code,
such that they can participate in documentation.
- Examples should be runnable - such that they are not getting out of
sync with underlying API/implementation.
In case of etcd-client, the examples are assuming running 'integration'
style, i.e. thay do connect to fully functional etcd-server.
That would lead to a cyclic dependencies between modules:
- server depends on client (as client need to be lightweight)
- client (for test purposes) depend on server.
Go modules does not allow to distingush testing dependency from
prod-code dependency.
Thus to meet the objective:
- The examples are getting executed within testing/integration packages against real etcd
- The examples are symlinked to 'unit' tests, such that they included in documentation.
- Long-term the unit examples should get rewritten to use 'mocks' instead of real integration tests.
Should fail following goword complains:
```
clientv3/config.go.48: // ("--max-request-bytes" flag to etcd or "embed.Config.MaxRequestBytes"). (spell: MaxRequestBytes -> ?)
clientv3/config.go.55: // ("--max-request-bytes" flag to etcd or "embed.Config.MaxRequestBytes"). (spell: MaxRequestBytes -> ?)
clientv3/leasing/doc.go.15: // Package leasing serves linearizable reads from a local cache by acquiring (spell: linearizable -> infeasible?)
clientv3/op.go.413: // it's linearizable. Serializable requests are better for lower latency (spell: linearizable -> infeasible?)
clientv3/retry.go.49: // an obvious server-side error (e.g. rpctypes.ErrRequestTooLarge). (spell: ErrRequestTooLarge -> Erectile?)
```
The module is supposed to contain minimal set of files that establish
public etcd server API. In particular client libraries for etcd built in
different languages might want to depend on this file.
client: Move client specific code (protos, version) to the api/
directory. Thanks to this change /client directory will not need to depend on
the server code. In next commits we make "/api" a module on its own.
Mechanical consequences of execution:
% git mv version/version.go api/version
% git mv etcdserver/api/v3rpc/rpctypes api/v3rpc
% git mv mvcc/mvccpb api/
% git mv etcdserver/etcdserverpb api/
% git mv auth/authpb api/
% git mv etcdserver/api/membership/membershippb api/
```
```
The flakes manifested as:
```
--- FAIL: TestV3WatchRestoreSnapshotUnsync (3.59s)
v3_watch_restore_test.go:82: inflight snapshot sends expected 0 or 1, got ""
FAIL
coverage: 55.2% of statements
FAIL go.etcd.io/etcd/v3/integration 3.646s
FAIL
```
The root reason is that all the SnapMsg processing happends on both ends
(leader, follower) assynchronously in goroutines, e.g. on Fifo schedule
within EtcdServer.run, so when we observe through metrics, we don't
know whether it finised (or even got started).
Idally we should have EtcdServer.Drain() call that exits when the server
processed or internal 'queues' and is idle.
The races was manifesting as following flakes:
```
```
See:
https://github.com/etcd-io/etcd/issues/12336
I'm taking the locks for short-duration of time (instead of the whole
duriation of Restore) to allow metrics being gather when the server
restoration is in progress.
```
{"level":"warn","ts":"2020-09-26T13:33:13.010Z","caller":"clientv3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"endpoint://client-c9c21e47-2013-4776-8e83-e331b2caa9ae/localhost:14422410081761184170","attempt":0,"error":"rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: connection error: desc = \"transport: Error while dialing dial unix localhost:14422410081761184170: connect: no such file or directory\""}
{"level":"warn","ts":"2020-09-26T13:33:13.011Z","caller":"clientv3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"endpoint://client-c9c21e47-2013-4776-8e83-e331b2caa9ae/localhost:14422410081761184170","attempt":0,"error":"rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: connection error: desc = \"transport: Error while dialing dial unix localhost:14422410081761184170: connect: no such file or directory\""}
{"level":"warn","ts":"2020-09-26T13:33:16.285Z","caller":"clientv3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"endpoint://client-b504e954-e000-42a4-aa4f-70ded8dbef39/localhost:55672762955698614610","attempt":0,"error":"rpc error: code = NotFound desc = etcdserver: requested lease not found"}
{"level":"warn","ts":"2020-09-26T13:33:21.434Z","caller":"clientv3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"endpoint://client-7945004b-f67e-42aa-af11-a7b40fbbe6fc/localhost:49623072144007561240","attempt":0,"error":"rpc error: code = Canceled desc = context canceled"}
==================
WARNING: DATA RACE
Write at 0x00c000905f78 by goroutine 764:
go.etcd.io/etcd/v3/mvcc.(*store).restore()
/go/src/go.etcd.io/etcd/mvcc/kvstore.go:397 +0x773
go.etcd.io/etcd/v3/mvcc.(*store).Restore()
/go/src/go.etcd.io/etcd/mvcc/kvstore.go:343 +0x5f1
go.etcd.io/etcd/v3/mvcc.(*watchableStore).Restore()
/go/src/go.etcd.io/etcd/mvcc/watchable_store.go:199 +0xe2
go.etcd.io/etcd/v3/etcdserver.(*EtcdServer).applySnapshot()
/go/src/go.etcd.io/etcd/etcdserver/server.go:1107 +0xa49
go.etcd.io/etcd/v3/etcdserver.(*EtcdServer).applyAll()
/go/src/go.etcd.io/etcd/etcdserver/server.go:1031 +0x6d
go.etcd.io/etcd/v3/etcdserver.(*EtcdServer).run.func8()
/go/src/go.etcd.io/etcd/etcdserver/server.go:986 +0x53
go.etcd.io/etcd/v3/pkg/schedule.(*fifo).run()
/go/src/go.etcd.io/etcd/pkg/schedule/schedule.go:157 +0x11e
Previous read at 0x00c000905f78 by goroutine 180:
[failed to restore the stack]
Goroutine 764 (running) created at:
go.etcd.io/etcd/v3/pkg/schedule.NewFIFOScheduler()
/go/src/go.etcd.io/etcd/pkg/schedule/schedule.go:70 +0x2b1
go.etcd.io/etcd/v3/etcdserver.(*EtcdServer).run()
/go/src/go.etcd.io/etcd/etcdserver/server.go:871 +0x32c
Goroutine 180 (running) created at:
net/http.(*Server).Serve()
/usr/local/go/src/net/http/server.go:2933 +0x5b6
net/http/httptest.(*Server).goServe.func1()
/usr/local/go/src/net/http/httptest/server.go:308 +0xd3
==================
--- FAIL: TestV3WatchRestoreSnapshotUnsync (6.74s)
testing.go:906: race detected during execution of test
FAIL
coverage: 83.5% of statements
FAIL go.etcd.io/etcd/v3/integration 231.272s
FAIL
Command 'go test -timeout=30m -cpu=1 --race --cover=true go.etcd.io/etcd/v3/integration' failed.
```
- We were leaking goroutines in auth-test
- The go-routines were depending / modifying global test environment
variables (simpleTokenTTLDefault) leading to races
Removed the leaked go-routines, and expanded 'auth' package to
be covered we leaked go-routines detection.
1. setting environment variable cannot be in quote
2. "--race" testing for unit tests is supposed to be part of linux-amd64-unit-4-cpu-race config.
3. 'run' function in test script should log_error in case of failed
command (wrong operator for ints comparison in bash).
* ./tests: Remove legacy coverage collection code
The legacy tests/cover.test.bash script was not ./test script
compatible for a long time.
The following method of coverage collection works (also across
packages) and does not make all the test execution slower.
```
COVERDIR=coverage PASSES="build build_cov cov" ./test
go tool cover -html ./coverage/cover.out
```
* CI: Reduce duplicated coverage between different variants on Travis
We used to execute unit tests in 3 different jobs,
every time with --race detection and every time in 3 variants:1,2,4
CPUS.
The proposed change makes each of the jobs use different variant of
CPUS, and only 4-cpu variant is running with --race detection
(as the more-parallel variant is more likely to experience races),
This commit adds support to check the 99th percentile of the etcd
members fsync duration and fires a critical alert when it is greater
than 1 sec. The recommended fsync for etcd is 20 ms but there might
be scenarios where a user might be using bad disks for reasons. This
will make sure to let the user/admin know that it is critical for
etcd performance.
Commit inspired by this failure:
https://travis-ci.com/github/etcd-io/etcd/jobs/391164537
This is not happanning locally - but can be forced by removal of go.sum
file. Let's watch how frequently we will need to refresh go.sum.
This refactoring offers following benefits:
- Unified way how go test commands are being called (in terms of flags intepretation)
- Uses standard go mechanisms (like go lists) to find files/packages that are subject for test. The mechanism are module aware.
- Added instruction how to install tools needed for the tests/checkers.
- Added colors to the output to make it easier to spot any failure.
Confirmed to work using:
- COVERDIR="./coverage" CPU="4" RACE=false COVER=false PASSES="build build_cov cov" ./test
- CPU="4" RACE=false COVER=false PASSES="e2e functional integration" ./test
- COVERDIR="./coverage" COVER="false" CPU="4" RACE="false" PASSES="fmt build unit build_cov integration e2e integration_e2e grpcproxy cov" ./test
- PASSES=unit PKG=./wal TIMEOUT=1m ./test
- PASSES=integration PKG=./clientv3 TIMEOUT=1m ./test
- PASSES=unit PKG=./wal TESTCASE=TestNew TIMEOUT=1m ./test
- PASSES=unit PKG=./wal TESTCASE="\bTestNew\b" TIMEOUT=1m ./test
- PASSES=integration PKG=./client/integration TESTCASE="\bTestV2NoRetryEOF\b" TIMEOUT=1m ./test
- COVERDIR=coverage PASSES="build_cov cov" ./test
To improve debuggability of `agreement among raft nodes before
linearized reading`, we added some tracing inside
`linearizableReadLoop`.
This will allow us to know the timing of `s.r.ReadIndex` vs
`s.applyWait.Wait(rs.Index)`.
Examplar flake: https://travis-ci.com/github/etcd-io/etcd/jobs/388806782
```
go test -timeout=5m -cpu=1 --run=Example ./client/...
ok go.etcd.io/etcd/v3/client 0.085s
testing: warning: no tests to run
PASS
Unexpected goroutines running after all test(s).
1 instances of:
text/template/parse.(*lexer).emit(...)
/usr/local/go/src/text/template/parse/lex.go:157
text/template/parse.lexText(...)
/usr/local/go/src/text/template/parse/lex.go:269 +0x4f0
text/template/parse.(*lexer).run(...)
/usr/local/go/src/text/template/parse/lex.go:230 +0x37
created by text/template/parse.lex
/usr/local/go/src/text/template/parse/lex.go:223 +0x190
FAIL go.etcd.io/etcd/v3/client/integration 0.013s
```
The grpc-proxy test logic was assuming that the context associated to client is closed,
while in practice all tests called client.Close() without explicit context close.
The current testing strategy is complicated 2 fold:
- grpc proxy works like man-in-the middle of each Connection issues
from integration tests and its lifetime is bound to the connection.
- both connections (client -> proxy, and proxy -> etcd-server) are
represented by the same ClientV3 object instance (with substituted
implementations of KV or watcher).
The fix splits context representing proxy from context representing proxy -> etcd-server connection,
thus allowing cancelation of the proxy context.
SubTraceStart and SubTraceEnd steps are only placeholders, not really
steps, we should skip them when logging the long duration steps,
otherwise these steps will lead to incorrect start time and duration
of subsequent steps.
This commit:
- Fires a critical alert when the etcd database quota is 95% full
at any given point of time to alert the user to defrag or increase
the quota in order to avoid the alarm getting triggered which blocks
all the writes to etcd meaning there can't be any new objects created.
This is needed to make sure the cluster supports running large number
of nodes and objects.
- Fires a warning when there is a sudden surge in etcd writes leading to
increase in the etcd database quota size at an alarming rate as it
is disruptive. It might be because of a rougue process and it's
important to alert the admin.
* etcdserver: check authinfo if it is not InternalAuthenticateRequest.
* credentials: let GetRequestMetadata() return nil when authToken isn't initialized.
* clientv3: get AuthToken gracefully without extra connection.
Direct syscalls using syscall.Syscall(SYS_*, ...) should no longer be
used on darwin, see [1]. Instead, use the fcntl libSystem wrappers
provided by the golang.org/x/sys/unix package which implement the same
functionality.
[1] https://golang.org/doc/go1.12#darwin
Fix test case errors in etcd-dump-logs and the error is the time zone.
When the GOST time zone is CST or PST and the test case will be failed.
So we should set UTC as the standard time zone.
Fixes:
go test -tags cluster_proxy ./clientv3/integration -v -run TestWatchRequestProgress
Does not fail the grpc-server (completely) by a not implemented RPC.
Failing whole server by remote request is anti-pattern and security
risk.
Prior to the fix, the command line above was failing with:
```
=== RUN TestWatchRequestProgress/0-watcher
panic: not implemented
goroutine 602 [running]:
go.etcd.io/etcd/v3/proxy/grpcproxy.(*watchProxyStream).recvLoop(0xc0004779d0, 0x0, 0x0)
/home/ptab/corp/etcd/proxy/grpcproxy/watch.go:275 +0xac5
go.etcd.io/etcd/v3/proxy/grpcproxy.(*watchProxy).Watch.func1(0xc0034f94a0, 0xc0004779d0)
/home/ptab/corp/etcd/proxy/grpcproxy/watch.go:129 +0x53
created by go.etcd.io/etcd/v3/proxy/grpcproxy.(*watchProxy).Watch
/home/ptab/corp/etcd/proxy/grpcproxy/watch.go:127 +0x3c8
FAIL go.etcd.io/etcd/v3/clientv3/integration 0.215s
FAIL
```
The flake happened e.g. in:
https://travis-ci.com/github/etcd-io/etcd/jobs/386607570
```
--- PASS: TestWatchClose (0.37s)
PASS
Unexpected goroutines running after all test(s).
1 instances of:
testing.runTests.func1.1(...)
/usr/local/go/src/testing/testing.go:1289 +0x60
created by testing.runTests.func1
/usr/local/go/src/testing/testing.go:1289 +0xdb
FAIL go.etcd.io/etcd/v3/clientv3/integration 344.389s
FAIL
```
This is implementation detail of Go testing.lib and we should not worry.
Currently our sample systemd service file `contrib/systemd/etcd.service`
have startup/shutdown dependency as below:
[Unit]
After=network.target
For some rare condition, e.g. bare matel deployment with slow network
startup, IP could not be assigned e arly enough before etcd default
`ETCD_HEARTBEAT_INTERVAL="100"` and `ETCD_ELECTION_TIMEOUT="1000"` get
timeouted, after graceful system reboot.
This cause etcd false negative classify itself use unhealthy, therefore
stop rejoining the remaining online cluster members.
This PR introduce:
- `etcd.service`: Ensure startup after `network-online.target` and
`time-sync.target`, so effective network connectivity and synced
time is available.
The logic is concept proof by
<https://github.com/alvistack/ansible-role-etcd/tree/develop>; also
works as expected with Ceph + Kubernetes deployment by
<https://github.com/alvistack/ansible-collection-kubernetes/tree/develop>.
No more deadlock happened during graceful system reboot, both AIO
single/multiple node with loopback mount.
Also see:
- <https://github.com/ceph/ceph/pull/36776>
- <https://github.com/etcd-io/etcd/pull/12259>
- <https://github.com/cri-o/cri-o/pull/4128>
- <https://github.com/kubernetes/release/pull/1504>
Signed-off-by: Wong Hoi Sing Edison <hswong3i@gmail.com>
Marked all 'integrational, e2e' as skipped in the --short mode.
Thanks to this we will be able to significantly simplify ./test script.
The run currently takes ~23s.
With (follow up) move of ~clientv3/snapshot to integration tests (as
part of modularization), we can expect this to fall to 5-10s.
```
% time go test --short ./... --count=1
ok go.etcd.io/etcd/v3 0.098s
? go.etcd.io/etcd/v3/Documentation/learning/lock/client [no test files]
? go.etcd.io/etcd/v3/Documentation/learning/lock/storage [no test files]
ok go.etcd.io/etcd/v3/auth 0.724s
? go.etcd.io/etcd/v3/auth/authpb [no test files]
ok go.etcd.io/etcd/v3/client 0.166s
ok go.etcd.io/etcd/v3/client/integration 0.166s
ok go.etcd.io/etcd/v3/clientv3 3.219s
ok go.etcd.io/etcd/v3/clientv3/balancer 1.102s
? go.etcd.io/etcd/v3/clientv3/balancer/connectivity [no test files]
? go.etcd.io/etcd/v3/clientv3/balancer/picker [no test files]
? go.etcd.io/etcd/v3/clientv3/balancer/resolver/endpoint [no test files]
ok go.etcd.io/etcd/v3/clientv3/clientv3util 0.096s [no tests to run]
ok go.etcd.io/etcd/v3/clientv3/concurrency 3.323s
? go.etcd.io/etcd/v3/clientv3/credentials [no test files]
ok go.etcd.io/etcd/v3/clientv3/integration 0.131s
? go.etcd.io/etcd/v3/clientv3/leasing [no test files]
? go.etcd.io/etcd/v3/clientv3/mirror [no test files]
ok go.etcd.io/etcd/v3/clientv3/namespace 0.041s
ok go.etcd.io/etcd/v3/clientv3/naming 0.115s
ok go.etcd.io/etcd/v3/clientv3/ordering 0.121s
ok go.etcd.io/etcd/v3/clientv3/snapshot 19.325s
ok go.etcd.io/etcd/v3/clientv3/yaml 0.090s
ok go.etcd.io/etcd/v3/contrib/raftexample 7.572s
? go.etcd.io/etcd/v3/contrib/recipes [no test files]
ok go.etcd.io/etcd/v3/embed 0.282s
ok go.etcd.io/etcd/v3/etcdctl 0.054s
? go.etcd.io/etcd/v3/etcdctl/ctlv2 [no test files]
ok go.etcd.io/etcd/v3/etcdctl/ctlv2/command 0.117s
? go.etcd.io/etcd/v3/etcdctl/ctlv3 [no test files]
ok go.etcd.io/etcd/v3/etcdctl/ctlv3/command 0.070s
ok go.etcd.io/etcd/v3/etcdmain 0.172s
ok go.etcd.io/etcd/v3/etcdserver 1.698s
? go.etcd.io/etcd/v3/etcdserver/api [no test files]
ok go.etcd.io/etcd/v3/etcdserver/api/etcdhttp 0.075s
ok go.etcd.io/etcd/v3/etcdserver/api/membership 0.104s
? go.etcd.io/etcd/v3/etcdserver/api/membership/membershippb [no test files]
ok go.etcd.io/etcd/v3/etcdserver/api/rafthttp 0.181s
ok go.etcd.io/etcd/v3/etcdserver/api/snap 0.078s
? go.etcd.io/etcd/v3/etcdserver/api/snap/snappb [no test files]
ok go.etcd.io/etcd/v3/etcdserver/api/v2auth 0.142s
ok go.etcd.io/etcd/v3/etcdserver/api/v2discovery 0.035s
ok go.etcd.io/etcd/v3/etcdserver/api/v2error 0.043s
ok go.etcd.io/etcd/v3/etcdserver/api/v2http 0.070s
ok go.etcd.io/etcd/v3/etcdserver/api/v2http/httptypes 0.031s
? go.etcd.io/etcd/v3/etcdserver/api/v2stats [no test files]
ok go.etcd.io/etcd/v3/etcdserver/api/v2store 0.645s
ok go.etcd.io/etcd/v3/etcdserver/api/v2v3 0.218s
? go.etcd.io/etcd/v3/etcdserver/api/v3alarm [no test files]
? go.etcd.io/etcd/v3/etcdserver/api/v3client [no test files]
ok go.etcd.io/etcd/v3/etcdserver/api/v3compactor 1.765s
? go.etcd.io/etcd/v3/etcdserver/api/v3election [no test files]
? go.etcd.io/etcd/v3/etcdserver/api/v3election/v3electionpb [no test files]
? go.etcd.io/etcd/v3/etcdserver/api/v3election/v3electionpb/gw [no test files]
? go.etcd.io/etcd/v3/etcdserver/api/v3lock [no test files]
? go.etcd.io/etcd/v3/etcdserver/api/v3lock/v3lockpb [no test files]
? go.etcd.io/etcd/v3/etcdserver/api/v3lock/v3lockpb/gw [no test files]
ok go.etcd.io/etcd/v3/etcdserver/api/v3rpc 0.091s
ok go.etcd.io/etcd/v3/etcdserver/api/v3rpc/rpctypes 0.012s
ok go.etcd.io/etcd/v3/etcdserver/cindex 0.054s
ok go.etcd.io/etcd/v3/etcdserver/etcdserverpb 0.039s
? go.etcd.io/etcd/v3/etcdserver/etcdserverpb/gw [no test files]
ok go.etcd.io/etcd/v3/functional/agent 0.094s
? go.etcd.io/etcd/v3/functional/cmd/etcd-agent [no test files]
? go.etcd.io/etcd/v3/functional/cmd/etcd-proxy [no test files]
? go.etcd.io/etcd/v3/functional/cmd/etcd-runner [no test files]
? go.etcd.io/etcd/v3/functional/cmd/etcd-tester [no test files]
ok go.etcd.io/etcd/v3/functional/rpcpb 0.060s
? go.etcd.io/etcd/v3/functional/runner [no test files]
ok go.etcd.io/etcd/v3/functional/tester 0.079s
ok go.etcd.io/etcd/v3/integration 0.684s
ok go.etcd.io/etcd/v3/integration/embed 0.101s
ok go.etcd.io/etcd/v3/lease 3.455s
ok go.etcd.io/etcd/v3/lease/leasehttp 2.185s
? go.etcd.io/etcd/v3/lease/leasepb [no test files]
ok go.etcd.io/etcd/v3/mvcc 7.246s
ok go.etcd.io/etcd/v3/mvcc/backend 0.354s
? go.etcd.io/etcd/v3/mvcc/mvccpb [no test files]
ok go.etcd.io/etcd/v3/pkg/adt 0.025s
? go.etcd.io/etcd/v3/pkg/contention [no test files]
? go.etcd.io/etcd/v3/pkg/cpuutil [no test files]
ok go.etcd.io/etcd/v3/pkg/crc 0.008s
? go.etcd.io/etcd/v3/pkg/debugutil [no test files]
ok go.etcd.io/etcd/v3/pkg/expect 0.015s
ok go.etcd.io/etcd/v3/pkg/fileutil 0.268s
ok go.etcd.io/etcd/v3/pkg/flags 0.021s
ok go.etcd.io/etcd/v3/pkg/httputil 0.020s
ok go.etcd.io/etcd/v3/pkg/idutil 0.008s
ok go.etcd.io/etcd/v3/pkg/ioutil 0.025s
ok go.etcd.io/etcd/v3/pkg/logutil 0.047s
? go.etcd.io/etcd/v3/pkg/mock/mockserver [no test files]
? go.etcd.io/etcd/v3/pkg/mock/mockstorage [no test files]
? go.etcd.io/etcd/v3/pkg/mock/mockstore [no test files]
? go.etcd.io/etcd/v3/pkg/mock/mockwait [no test files]
ok go.etcd.io/etcd/v3/pkg/netutil 1.024s
ok go.etcd.io/etcd/v3/pkg/osutil 0.021s
ok go.etcd.io/etcd/v3/pkg/pathutil 0.008s
ok go.etcd.io/etcd/v3/pkg/pbutil 0.008s
ok go.etcd.io/etcd/v3/pkg/proxy 4.081s
ok go.etcd.io/etcd/v3/pkg/report 0.008s
? go.etcd.io/etcd/v3/pkg/runtime [no test files]
ok go.etcd.io/etcd/v3/pkg/schedule 0.009s
ok go.etcd.io/etcd/v3/pkg/srv 0.019s
ok go.etcd.io/etcd/v3/pkg/stringutil 0.008s
? go.etcd.io/etcd/v3/pkg/systemd [no test files]
ok go.etcd.io/etcd/v3/pkg/testutil 0.023s
ok go.etcd.io/etcd/v3/pkg/tlsutil 3.965s
ok go.etcd.io/etcd/v3/pkg/traceutil 0.034s
ok go.etcd.io/etcd/v3/pkg/transport 0.532s
ok go.etcd.io/etcd/v3/pkg/types 0.028s
ok go.etcd.io/etcd/v3/pkg/wait 0.023s
ok go.etcd.io/etcd/v3/proxy/grpcproxy 0.101s
? go.etcd.io/etcd/v3/proxy/grpcproxy/adapter [no test files]
? go.etcd.io/etcd/v3/proxy/grpcproxy/cache [no test files]
ok go.etcd.io/etcd/v3/proxy/httpproxy 0.044s
ok go.etcd.io/etcd/v3/proxy/tcpproxy 0.047s
ok go.etcd.io/etcd/v3/raft 0.312s
ok go.etcd.io/etcd/v3/raft/confchange 0.183s
ok go.etcd.io/etcd/v3/raft/quorum 0.316s
ok go.etcd.io/etcd/v3/raft/raftpb 0.024s
ok go.etcd.io/etcd/v3/raft/rafttest 0.640s
ok go.etcd.io/etcd/v3/raft/tracker 0.026s
ok go.etcd.io/etcd/v3/tests/e2e 0.077s
? go.etcd.io/etcd/v3/tools/benchmark [no test files]
? go.etcd.io/etcd/v3/tools/benchmark/cmd [no test files]
? go.etcd.io/etcd/v3/tools/etcd-dump-db [no test files]
ok go.etcd.io/etcd/v3/tools/etcd-dump-logs 0.088s
? go.etcd.io/etcd/v3/tools/etcd-dump-metrics [no test files]
? go.etcd.io/etcd/v3/tools/local-tester/bridge [no test files]
? go.etcd.io/etcd/v3/version [no test files]
ok go.etcd.io/etcd/v3/wal 1.517s
? go.etcd.io/etcd/v3/wal/walpb [no test files]
go test --short ./... --count=1 76.12s user 12.57s system 375% cpu 23.635 total
```
As we get rid of ./vendor there is no need to update the dependencies.
If anyone needs up-to-date vendor directory locally, getting it is as
simple as:
```go mod vendor```
Fixes:
go test --tags cluster_proxy --timeout=30m -run TestLeasingTxnOwnerGet -v ./clientv3/integration/...
The explicit code to close client is needed due to:
76e769ce95/clientv3/watch.go (L72)
as just ctx close by LeasingKeyValue store does not interrupts opened Watches.
The only way to interrupt open Watch is to close the 'whole' Watcher / Client.
The code used to:
- report time since previous compaction success as a 'duration' of compaction process itself.
- mix real clock with 'injected' clock. This led to strange log-lines
in tests in order of 234543543h of duration.
Added check that ensures that go.mod & go.sum files are up-to-date.
The check verifies whether 'go mod tidy' does not generate any mutations
in these files.
The check can be run on its own:
PASSES="mod_tidy" ./test
Or as part of "fmt" pass:
PASSES="fmt" ./test
Examplar outputs:
```
% PASSES="fmt" ./test
Running with TEST_CPUS: 1,2,4
Starting 'fmt' pass at Fri 11 Sep 2020 11:07:54 PM CEST
'shellcheck' started at Fri 11 Sep 2020 11:07:54 PM CEST
'shellcheck' completed at Fri 11 Sep 2020 11:07:54 PM CEST
'markdown_you' started at Fri 11 Sep 2020 11:07:54 PM CEST
'markdown_you' completed at Fri 11 Sep 2020 11:07:54 PM CEST
'goword' started at Fri 11 Sep 2020 11:07:54 PM CEST
'goword' completed at Fri 11 Sep 2020 11:07:54 PM CEST
'gofmt' started at Fri 11 Sep 2020 11:07:54 PM CEST
'gofmt' completed at Fri 11 Sep 2020 11:07:55 PM CEST
'govet' started at Fri 11 Sep 2020 11:07:55 PM CEST
'govet' completed at Fri 11 Sep 2020 11:07:57 PM CEST
'revive' started at Fri 11 Sep 2020 11:07:57 PM CEST
Skipping revive...
'revive' completed at Fri 11 Sep 2020 11:07:57 PM CEST
'license_header' started at Fri 11 Sep 2020 11:07:57 PM CEST
'license_header' completed at Fri 11 Sep 2020 11:07:58 PM CEST
'receiver_name' started at Fri 11 Sep 2020 11:07:58 PM CEST
'receiver_name' completed at Fri 11 Sep 2020 11:07:58 PM CEST
'commit_title' started at Fri 11 Sep 2020 11:07:58 PM CEST
'commit_title' completed at Fri 11 Sep 2020 11:07:58 PM CEST
'mod_tidy' started at Fri 11 Sep 2020 11:07:58 PM CEST
*** /tmp/fileiALKRA_go.mod 2020-09-11 23:07:58.838010716 +0200
--- ./go.mod 2020-09-11 23:07:58.974010922 +0200
***************
*** 29,39 ****
github.com/mattn/go-runewidth v0.0.2 // indirect
github.com/modern-go/reflect2 v1.0.1
github.com/olekukonko/tablewriter v0.0.0-20170122224234-a0225b3f23b5
github.com/prometheus/client_golang v1.0.0
github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4
- github.com/prometheus/common v0.4.1
github.com/sirupsen/logrus v1.4.2 // indirect
github.com/soheilhy/cmux v0.1.4
github.com/spf13/cobra v0.0.3
github.com/spf13/pflag v1.0.1
github.com/tmc/grpc-websocket-proxy v0.0.0-20170815181823-89b8d40f7ca8
--- 29,38 ----
./go.mod is not in sync with 'go mod tidy'
```
```
% PASSES="mod_tidy" ./test
Running with TEST_CPUS: 1,2,4
Starting 'mod_tidy' pass at Fri 11 Sep 2020 11:09:21 PM CEST
*** /tmp/file9gy4so_go.mod 2020-09-11 23:09:21.166133290 +0200
--- ./go.mod 2020-09-11 23:09:21.286133466 +0200
***************
*** 29,39 ****
github.com/mattn/go-runewidth v0.0.2 // indirect
github.com/modern-go/reflect2 v1.0.1
github.com/olekukonko/tablewriter v0.0.0-20170122224234-a0225b3f23b5
github.com/prometheus/client_golang v1.0.0
github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4
- github.com/prometheus/common v0.4.1
github.com/sirupsen/logrus v1.4.2 // indirect
github.com/soheilhy/cmux v0.1.4
github.com/spf13/cobra v0.0.3
github.com/spf13/pflag v1.0.1
github.com/tmc/grpc-websocket-proxy v0.0.0-20170815181823-89b8d40f7ca8
--- 29,38 ----
./go.mod is not in sync with 'go mod tidy'
```
To fix a panic that happens when trying to get ids of etcd members in
force new cluster mode, the issue happen if the cluster previously had
etcd learner nodes added to the cluster
Fixes#12285
Currently, the grpc gateway is enabled by default when run the etcd server
using command line configuration. However, when provide config through
config file, the grpc gateway is disabled by default. We should either use
the same approach or at least document this.
related #https://github.com/etcd-io/etcd/issues/12093
grpc proxy opens additional 2 watching channels. The metric is shared
between etcd-server & grpc_proxy, so all assertions on number of open
watch channels need to take in consideration the additional "2"
channels.
Prior to the fix:
```
go test -mod=mod -timeout 30m -tags cluster_proxy "./integration/..."
```
Was failing with:
```
integration/cluster_proxy.go:58:37: not enough arguments in call to grpcproxy.NewWatchProxy
have (*clientv3.Client)
want (*zap.Logger, *clientv3.Client)
FAIL go.etcd.io/etcd/v3/integration [build failed]
```
This CL fixes:
COVERDIR=./coverage PASSES="build_cov" && go test --tags cov -v ./tests/e2e
and is part of the effort to make:
COVERDIR=coverage PASSES="build_cov cov" ./test
fully pass.
The args passed to ./bin/etcd_test and ./bin/etcdctl_test binaries were
mismatched. The protocol of passing the arguments using
environment variables has been replaces with proper passing of flags.
How the measurement of coverage by e2e tests works:
1. COVERDIR=./coverage PASSES="build_cov" are generating
./bin/etcd_test and ./bin/etcdctl_test binaries.
2. These binaries are tests (as coverage can be computed only for
tests) [see ./main_test.go ./etcdctl/main_test.go], but this tests are
running the main logic of the server and uppon termination (or SIGTERM
signal) are writting proper .coverprofile files in the $COVERDIR folder.
The binaries used to take arguments using env variables, but its not
needed any longer. The binaries can consume any command line arguments
that either test (so --test.fooo) or the original binary can consume.
3. The tests/e2e (when compiled with the --tags cov) are starting the
_test binaries instead of the original binaries, such that the coverage
is being collected.
Change tests/e2e to use proper (client-nocn.crt) certificate when
running in tags="cluster_proxy" mode.
Thanks to this (and previous in this PR) changes, the following test run
finally succeeds:
./build && go test --tags "cluster_proxy" -v ./tests/e2e/...
We have following communication schema:
client --- 1 ---> grpc-proxy --- 2 --- > etcd-server
There are 2 sets of flags/certs in grpc proxy [ https://github.com/etcd-io/etcd/blob/master/etcdmain/grpc_proxy.go#L140 ]:
A. (cert-file, key-file, trusted-ca-file, auto-tls) this are controlling [1] so client to proxy connection and in particular they are describing proxy public identity.
B. (cert,key, cacert ) - these are controlling [2] so what's the identity that proxy uses to make connections to the etcd-server.
If 2 (B.) contains certificate with CN and etcd-server is running with --client-cert-auth=true, the CN can be used as identity of 'client' from service perspective. This is permission escalation, that we should forbid.
If 1 (A.) contains certificate with CN - it should be considered perfectly valid. The server can (should) have full identity.
So only --cert flag (and not --cert-file flag) should be validated for empty CN.
Executed:
(cd ./integration/fixtures && ./gencerts.sh)
This in particular cereated a new client-nocn.crt (and key) that can be
used for testing grpc-proxy -> etcd-server connections.
integration/fixtures/gencerts.sh:
- refactored common logic to a helper function
- added definition for client-nocn certificate
(used for grpc-proxy -> etcd-server) communication.
This is to aid with debugging the effectiveness of systems that
manually take care of cluster compaction, and have greater visibity
into recent compactions.
It can be handy to alert on the exactly how long it was since a
compaction (and also to put on dashboards) had happened.
---
Tested using a test cluster, the final result looks like this:
```
root@etcd-1:~# ETCDCTL_API=3 /tmp/test-etcd/etcdctl --endpoints=192.168.232.10:2379 compact 1012
compacted revision 1012
root@etcd-1:~# curl -s 192.168.232.10:2379/metrics | grep last
# HELP etcd_debugging_mvcc_db_compaction_last The unix time since the last db compaction. Resets to 0 on start.
# TYPE etcd_debugging_mvcc_db_compaction_last gauge
etcd_debugging_mvcc_db_compaction_last 1.595873939e+09
```
From etcd-dev discussion:
https://groups.google.com/u/2/g/etcd-dev/c/oMGSBqs_7sc
I have been working on this system called Asset Transparency[1] which
helps users verify they have received the correct contents from a URL.
If you are familiar with the "download a file, download a SHA256SUM
file, run `sha256sum -c`, etc" process? This tool helps to automate
that for users into something like this[2]:
$ tl get https://github.com/etcd-io/etcd/releases/download/v3.4.12/etcd-v3.4.12-darwin-amd64.zip
And a best practice for this Asset Transparency system is that URLs
are registered with the log as soon as possible. Why? Well, the sooner
a URL is entered the longer it can protect people consuming a URL from
unexpected content modification from say a GitHub credential
compromise.
To that end I have written a GitHub Action[3] that will automatically
do that on every release. It is easy to activate and should be hands
free after installation. So, before I enable it I want to see if there
are any concerns from maintainers. The only change to our repo will be
a new file in .github/workflows.
[1] https://www.transparencylog.com
[2] https://github.com/transparencylog/tl
[3] https://github.com/transparencylog/publish-releases-asset-transparency-action
Similar counts are exposed via Prometheus.
This adds the one that are perceived by etcd server.
e.g.
os_fd_limit 120000
os_fd_used 14
process_cpu_seconds_total 0.31
process_max_fds 120000
process_open_fds 17
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
The test is vary flaky on Travis.
Seems that since (https://github.com/etcd-io/etcd/issues/7724) the
client is expected to simply ignore whether server is in AuthDisabled
mode even if the user supplies credentials.
The tests used to:
* use very large cluster (10 nodes)
* set very low timeout (1 sec)
Such setup led to frequent deadlineExceed errors or following failures:
=== RUN TestGetTokenWithoutAuth
{"level":"warn","ts":"2020-08-04T16:50:48.686+0200","caller":"clientv3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"endpoint://client-35573307-1ee5-441b-acc7-d073f0bd7de5/localhost:69820396562031027440","attempt":0,"error":"rpc error: code = Unavailable desc = etcdserver: leader changed"}
user_test.go:151: other errors:etcdserver: leader changed
--- FAIL: TestGetTokenWithoutAuth (10.91s)
The source of problem was the fact that multiple tests were creating
their clusters (and some of them were setting global grpclog).
If the test was running after some other test that created HttpServer
(so accessed grpclog), this was reported as race.
Tested with:
go test ./clientv3/. -v "--run=(Example).*" --count=2
go test ./clientv3/. -v "--run=(Test).*" --count=2
go test ./integration/embed/. -v "--run=(Test).*" --count=2
Fixes following problems during "./etcd# go test ./..."
> go.etcd.io/etcd/v3/etcdserver/api/v2store_test
etcdserver/api/v2store/store_test.go:847:24: conversion from int to string yields a string of one rune, not a string of digits (did you mean fmt.Sprint(x)?)
> go.etcd.io/etcd/v3/wal
wal/wal_test.go:242:68: conversion from int to string yields a string of one rune, not a string of digits (did you mean fmt.Sprint(x)?)
The fix is needed to mitigate consequences of
https://github.com/golang/go/issues/29458 "golang breaking change" that
causes following test failures on etcd end:
--- FAIL: TestCtlV2Set (0.00s)
ctl_v2_test.go:552: could not start etcd process cluster (fork/exec ../../bin/etcd: Setctty set but Ctty not valid in child)
--- FAIL: TestCtlV2SetQuorum (0.00s)
ctl_v2_test.go:552: could not start etcd process cluster (fork/exec ../../bin/etcd: Setctty set but Ctty not valid in child)
--- FAIL: TestCtlV2SetClientTLS (0.00s)
ctl_v2_test.go:552: could not start etcd process cluster (fork/exec ../../bin/etcd: Setctty set but Ctty not valid in child)
Before this change, the default window for the etcdMembersDown network failure
rate function was recently changed to 1 minute. While this helps detect a etcd
recovery more quickly, it depends on scrape intervals of <= 15s to collect
sufficient data points for the rate function. In practice, an interval of >= 30s
is more typical, which causes the rate function to be less accurate.
This patch increases the window to 2m, which is a compromise between the
original value of 3m and the 1m change introuced with 2aa5684, and should
accomodate more typical scrape intervals.
To offset the window change and to further improve the chance that the alert
will only fire when etcd is truly dead, this patch changes the `for` clause from
3m to 10m. The rationale is as follows:
1. There can be significant variance in durations following a reboot before etcd
is scraped and detected as available.
2. A conservative trigger like 10m seems less likely to produce a false alarm in
the face of such variance.
3. In this alerting situation, if the outage is real, it seems unlikely that an
additional 7 minutes of delay before (for example) paging somebody will make a
significant impact on the overall response.
* etcd-mixin: Reformulate alerting rules to use `without` rather than `by`
With aggregations using `by`, all additional target labels that a user
might have configured, are aggregated away. However, those target
labels are useful for e.g. alert routing. With this commit, nothing
should change for vanilla job/instance target labels, but whoever has
more target labels can now still make use of them.
Signed-off-by: beorn7 <beorn@grafana.com>
* etcd-mixin: Parametrize instance labels to aggregate away
Signed-off-by: beorn7 <beorn@grafana.com>
* raft: check conf change before campaign
Signed-off-by: Jay Lee <BusyJayLee@gmail.com>
* raft: extract hup function
Signed-off-by: Jay Lee <BusyJayLee@gmail.com>
* raft: check pending conf change for transferleader
Signed-off-by: Jay Lee <BusyJayLee@gmail.com>
Tested conditions that cause
panic: invalid Go type int for field k8s_io.kubernetes.vendor.go_etcd_io.etcd.etcdserver.etcdserverpb.loggablePutRequest.value_size
Signed-off-by: Ed Bartosh <eduard.bartosh@intel.com>
Before this change, during a reboot in which etcd recovers quickly (e.g. 1 min),
the etcdMembersDown alert tends to fire even when etcd is fully healthy because
the averaging function can take more than 3 minutes to average back down below
the 0.01 threshold.
This change tries to reduce the possibility of a false negative by considering a
shorter (1 min) failure rate window which tends to average down below the
threshold far more quickly (within 1 min). The `for` clause of the alert should
ensure that the alert still fires if the poor conditions are sustained for an
unreasonable overall time (3 min).
A cluster with three members could see three leader changes during a
healthy rolling reboot, and we don't want to alert on that. Growing
to 4 reduces false-alarms for clusters with three or fewer members,
and that's probably most clusters. It will also slightly increase the
risk of false-negatives, but if the cluster is struggling with high
latency, it seems likely that it would quickly pass the new threshold
too.
The hard-coded threshold means that we are still likely to get
false-positives during rolling reboots of clusters with four or more
members. Ideally we'd scale this with the cluster size, or something,
but I'm not sure how to do that. Three members is the minimum size
for high availability, so reducing false positives for that case seems
worth addressing even if we leave larger clusters largely unchanges.
Also manually catch etcd3_alert.rules up to speed, since it seems to
have been passed over by 16fc8a2b4b (Documentation/op-guide:
Re-generate alert rules and dashboard from mixin, 2020-04-07, #11768).
backend: Create base type for readTx and concurrentReadTx
backend: Implemented review comments to rename rTx to baseReadTx and remove TODO
backend: Resolved comments around baseReadTx
backend: Implemented a review comment
os.MkdirAll creates directory before umask so make sure that a desired
permission is set after creating a directory with MkdirAll. Use the
existing TouchDirAll function which checks for permission if dir is already
exist and when create a new dir.
This ticker will check File Descriptor Requirements ,and count all fds in used.
And recorded some logs when in used >= limit/5*4. Just recorded message.
If fds was more than 10K,It's low performance due to FDUsage() works.
So need to increase it.
see https://github.com/etcd-io/etcd/issues/11969 for more detail.
This makes it possible to run an etcd node for testing and development
without placing lots of load on the file system.
Fixes#11930.
Signed-off-by: David Crawshaw <crawshaw@tailscale.com>
I've seen some cases SHA blobs are missing (still investigating).
Adding a check to make sure snapshot save always downloads
hash digests for integrity checks.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
Updates the base image for all arch releases to the new location (us.gcr.io/k8s-artifacts-prod/build-image) as well as to the latest version (v2.1.0). This should fix a number of vulnerabilities that are in the 1.0.0 base image release.
The watch count metrics are not robust to duplicate cancellations. These
cause the count to be decremented twice, leading eventually to negative
counts. We are seeing this in production. The duplicate cancellations
themselves are not themselves a big problem (except performance), but
they are caused by the new proactive cancellation logic (#11850) which
cancels proactively even immediately before initiating a Close, thus
nearly guaranteeing a Close-cancel race, as discussed in
watchable_store.go. We can avoid this in most cases by not sending a
cancellation when we are going to Close.
Currently, watch cancel requests are only sent to the server after a
message comes through on a watch where the client has cancelled. This
means that cancelled watches that don't receive any new messages are
never cancelled; they persist for the lifetime of the client stream.
This has negative connotations for locking applications where a watch
may observe a key which might never change again after cancellation,
leading to many accumulating watches on the server.
By cancelling proactively, in most cases we simply move the cancel
request to happen earlier, and additionally we solve the case where the
cancel request would never be sent.
Fixes#9416
Heavy inspiration drawn from the solutions proposed there.
emails here can be an unnecessary maintainance. The provided
GitHub IDs have the latest emails and also the process has
security@etcd.io mentioned in this doc as a contact email.
This change makes the etcd package compatible with the existing Go
ecosystem for module versioning.
Used this tool to update package imports:
https://github.com/KSubedi/gomove
Currently grpc-proxy doesn't config keep alive related options, so it
will use the default values provided by the underlay gprc library. If
clients uses a keep alive ping interval smaller than server's default
minTime, connections between server and clients will be closed and
reopened frequently.
There are open issues and pull requests that are years old on the etcd
repo and hundreds of issues that remain open.
Unfortunately it is just far outside the ability of the maintainer team
to take care of all of these issues manually.
So, follow the lead of Kubernetes and introduce a bot that closes PRs
and issues if they are stale.
See more information here: https://github.com/probot/stale#probot-stale
* etcdserver: add trace for txn request
* pkg/traceutil: added StopSubTrace as a sign of the end of subtrace. Added test case for logging out subtrace.
Method `kvsToEvents` can take a long time if a large number of events need to be synchronized. However, this method does not access any shared resources, so it no need to hold the tx lock when executing. So we can move it outside to reduce lock holding time.
To make it easier to root-cause when /health check fails.
For example, we are using load balancer to health check
each etcd instance, and when one etcd node gets terminated,
it's hard to tell whether etcd "server" was really failing
or client (or load balancer") failed to reach the etcd cluster
which is also failure in load balancer health check.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
Small refactoring of
`go.etcd.io/etcd/etcdserver/api/etcdhttp/metrics.go.checkHealth`
function just to avoid anoying repeatings of `if h.Health == "true" {`
* Documentation: enhance description of lock and lease
* Documentation: an executable implementation of fencing
* docs: api guarantees
cleanup lease grammar slightly
* docs: learning/lock/README.md improve grammar
Co-Authored-By: Steven E. Harris <seh@panix.com>
* docs: learning: improve locks and leases grammar
Co-authored-by: Brandon Philips <brandon@ifup.org>
Co-authored-by: Steven E. Harris <seh@panix.com>
Apps typically maintain the raft configuration as part of the state
machine. As a result, they want to be able to reject configuration change
entries at apply time based on the state on which the entry is supposed
to be applied. When this happens, the app should not call
ApplyConfChange, but the comments did not make this clear.
As a result, it was tempting to pass an empty pb.ConfChange or it's V2
version instead of not calling ApplyConfChange.
However, an empty V1 or V2 proto aren't noops when the configuration is
joint: an empty V1 change is treated internally as a single
configuration change for NodeID zero and will cause a panic when applied
in a joint state. An empty V2 proto is treated as a signal to leave a
joint state, which means that the app's config and raft's would diverge.
The comments updated in this commit now ask users to not call
ApplyConfState when they reject a conf change. Apps that never use joint
consensus can keep their old behavior since the distinction only matters
when in a joint state, but we don't want to encourage that.
The code doing so was undertested and buggy: it would launch multiple
attempts to transition out when the conf change was not the last element
in the log.
This commit fixes the problem and adds a regression test. It also
reworks the code to handle a former untested edge case, in which the
auto-transition append is refused. This can't happen any more with the
current version of the code because this proposal has size zero and is
special cased in increaseUncommittedSize. Last but not least, the
auto-leave proposal now also bumps pendingConfIndex, which was not done
previously due to an oversight.
When promoting a learner member we should not count already a voting
member, but take only into account the number of existing voting
members and their current status (started, unstarted) when taking the
decision whether a learner member can be promoted.
Before this change, it was impossible to grow from a quorum N to a N+1
through promoting a learning member.
Fixes: #11633
When an etcd instance attempts to perform service discovery, if a
cluster size with negative value is provided, the etcd instance
will panic without recovery because of
When no Alarms are found, the response has no header. The header should always
be populated. Some components, like fields printer used by etcdctl, break when
the header is not populated.
Fixes#11581
Signed-off-by: Daniel Lipovetsky <dlipovetsky@d2iq.com>
This changes have started at etcdctl under auth.go, and make changes to stub out everything down into the internal raft. Made changes to the .proto files and regenerated them so that the local version would build successfully.
The `etcdHighNumberOfLeaderChanges` alert had a copy and paste
error when it was converted from docs to mixin in 10244 - we moved
from "increase over 15m > 3" to "rate over 15m > 3" which is not
the same (rate is measured per second, so it should have been
"rate over 15m > (3 / 60 / 15)"). As part of fixing that, we
need to capture when prometheus starts or when new etcd clusters
are captured with a high leader change - i.e. if you start a new
etcd cluster and at the moment prometheus first scrapes you are
already at 5 leader changes, we should fire on that transition.
This alert is also now more responsive, so if you get a quick
burst of 3 leader changes we'll alert within 5m rather than 15m.
Added ClusterVersionSetRequest for setting cluster version via v3 apply.
Added ClusterMemberAttrSetRequest for setting clsuter member attributes
via v3 apply.
Some goroutines in test functions will be leaked in certain cases.
This patch stops these leaks no matter what happens in test, by
putting the blocking channel in select together with a new stopc
channel, or adding 1 buffer to the blocking channel.
Version flag is meant for displaying version and it's a boolean.
It's for an internal use, and we may not want users to set
it in the environment.
Fixes # 11210
Etcd-backup-restore is collection of components to backup and restore the etcd. It features the periodic full and incremental backups, automated restore, Validation of etcd data directory with multi cloud provider support.
steps:range from the in-memory index tree; range from boltdb.
etcdserver: add tracing steps: agreement among raft nodes before
linerized reading; authentication; filter and sort kv pairs; assemble
the response.
In case of URLs that are synonyms, the current lexicographic sorting
and compare of the URLs fails with frustrating errors. Make sure to do
a full comparison between every set of PeerURLs before failing.
Fixes#11013
TryLock locks the mutex if not already locked by another session.
If lock is held by another session, return immediately after attempting necessary cleanup
Added integration test
Fixes#10493
The tool takes default values but it was not visible which default
values were taken. Added default values in proper place, and added a
newline at the end of output.
In go1.13, the TLS13 is enablled by default, and as per go1.13 release notes :
TLS 1.3 cipher suites are not configurable. All supported cipher suites are safe,
and if PreferServerCipherSuites is set in Config the preference order is based
on the available hardware.
Fixing the test case for go1.13 by limiting the TLS version to TLS12
In the Background section, the document describes various challenges for cluster membership change.
Added section header for each case described for better readability.
When a leader removes itself, it will retain its leadership but not
accept new proposals, making the range effectively stuck until manual
intervention triggers a campaign event.
This commit documents the behavior. It does not correct it yet.
Verifiy the behavior in various v1 and v2 conf change operations.
This also includes various fixups, notably it adds protection
against transitioning in and out of new configs when this is not
permissible.
There are more threads to pull, but those are left for future commits.
New tool: ETCD Manager
ETCD Manager is a multi-platform ETCD v3 client. Currently, builds are available form Mac, Wiindows and Linux, but iOS / Android builds will also be added in the future.
It aims to be a modern, efficient and easy to use GUI with full coverage of ETCD APIs / functionality. The first public (beta) release is already available.
When the leader applied a new configuration that added voters, it would
not immediately probe these voters, delaying when they would be caught
up.
I noticed this while writing an interaction-driven test, which has now
been cleaned up and completed.
It is a helper case to attach a debugger to when a problem needs
to be investigated in a longer test file. In such a case, add the
following stanza immediately before the interesting behavior starts:
_breakpoint:
----
ok
and set a breakpoint on the _breakpoint case.
Initializing at LastIndex+1 meant that new peers would not be probed
immediately when they appeared in the leader's config, which delays
their getting caught up.
It has often been tedious to test the interactions between multi-member
Raft groups, especially when many steps were required to reach a certain
scenario. Often, this boilerplate was as boring as it is hard to write
and hard to maintain, making it attractive to resort to shortcuts
whenever possible, which in turn tended to undercut how meaningful and
maintainable the tests ended up being - that is, if the tests were even
written, which sometimes they weren't.
This change introduces a datadriven framework specifically for testing
deterministically the interaction between multiple members of a raft group
with the goal of reducing the friction for writing these tests to near
zero.
In the near term, this will be used to add thorough testing for joint
consensus (which is already available today, but wildly undertested),
but just converting an existing test into this framework has shown that
the concise representation and built-in inspection of log messages
highlights unexpected behavior much more readily than the previous unit
tests did (the test in question is `snapshot_succeed_via_app_resp`; the
reader is invited to compare the old and new version of it).
The main building block is `InteractionEnv`, which holds on to the state
of the whole system and exposes various relevant methods for
manipulating it, including but not limited to adding nodes, delivering
and dropping messages, and proposing configuration changes. All of this
is extensible so that in the future I hope to use it to explore the
phenomena discussed in
https://github.com/etcd-io/etcd/issues/7625#issuecomment-488798263
which requires injecting appropriate "crash points" in the Ready
handling loop. Discussions of the "what if X happened in state Y"
can quickly be made concrete by "scripting up an interaction test".
Additionally, this framework is intentionally not kept internal to the
raft package.. Though this is in its infancy, a goal is that it should
be possible for a suite of interaction tests to allow applications to
validate that their Storage implementation behaves accordingly, simply
by running a raft-provided interaction suite against their Storage.
While writing interaction tests for joint configuration changes, I
realized that this wasn't working yet - restoring had no notion of
the joint configuration and was simply dropping it on the floor.
This commit introduces a helper `confchange.Restore` which takes
a `ConfState` and initializes a `Tracker` from it.
This is then used both in `(*raft).restore` as well as in `newRaft`.
Useful for deciding when to terminate the unhealthy follower.
If the follower is receiving a leader snapshot, operator may wait.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
add 1-size buffer for `errc` to avoid deadlock of child goroutine
add a local variable to a void data race in `err`
when `case <-stream.Context().Done():` is taken
This is helpful for upcoming testing work which allows datadriven
testing of the interaction of multiple nodes. This testing requires
determinism to work correctly.
See the issue created here:
https://github.com/etcd-io/etcd/issues/10989#issuecomment-518726038
doc: fix broken links referring to etcd.redhatdocs.io
Adding links to internal Documentation within github.com.
Update runtime-configuration.md
Update runtime-configuration.md
Update CHANGELOG-3.3.md
Remove extra space
Keep the formatting similar to original
It turns out that that learners must be allowed to cast votes.
This seems counter- intuitive but is necessary in the situation in which
a learner has been promoted (i.e. is now a voter) but has not learned
about this yet.
For example, consider a group in which id=1 is a learner and id=2 and
id=3 are voters. A configuration change promoting 1 can be committed on
the quorum `{2,3}` without the config change being appended to the
learner's log. If the leader (say 2) fails, there are de facto two
voters remaining. Only 3 can win an election (due to its log containing
all committed entries), but to do so it will need 1 to vote. But 1
considers itself a learner and will continue to do so until 3 has
stepped up as leader, replicates the conf change to 1, and 1 applies it.
Ultimately, by receiving a request to vote, the learner realizes that
the candidate believes it to be a voter, and that it should act
accordingly. The candidate's config may be stale, too; but in that case
it won't win the election, at least in the absence of the bug discussed
in:
https://github.com/etcd-io/etcd/issues/7625#issuecomment-488798263.
An etcd member being down is an important failure state - while
normal admin operations may cause transient outages to rotate,
when any member is down the cluster is operating in a degraded
fashion. Add an alert that records when any members are down
so that administrators know whether the next failure is fatal.
The rule is more complicated than `up{...} == 0` because not all
failure modes for etcd may have an `up{...}` entry for each member.
For instance, a Kubernetes service in front of an etcd cluster
might only have 2 endpoints recorded in `up` because the third
pod is evicted by the kubelet - the cluster is degraded but
`count(up{...})` would not return the full quorum size. Instead,
use network peer send failures as a failure detector and attempt
to return the max of down services or failing peers. We may
undercount the number of total failures, but we will at least
alert that a member is down.
Make log level configurable, and deprecate "debug" flag in v3.5.
And adds more warnings on flags that's being deprecated in v3.5.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
Overwrite authority when it's IP.
When user dials with "grpc.WithDialer", "grpc.DialContext" "cc.parsedTarget"
update only happens once. This is problematic, because when TLS is enabled,
retries happen through "grpc.WithDialer" with static "cc.parsedTarget" from
the initial dial call.
If the server authenticates by IP addresses, we want to set a new endpoint as
a new authority. Otherwise
"transport: authentication handshake failed: x509: certificate is valid for 127.0.0.1, 192.168.121.180, not 192.168.223.156"
when the new dial target is "192.168.121.180" whose certificate host name is also "192.168.121.180"
but client tries to authenticate with previously set "cc.parsedTarget" field "192.168.223.156"
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
This fixes an index out-of-bounds panic caused when using the embed
package and the zap logger. When a TLS handshake error is logged, the
slice for cert ip addresses is allocated with capacity but no length, so
subsequent index access causes the panic, and doesn't surface the TLS
handshake error to the user.
Fixes#10932
I changed `(*RawNode).Ready`'s behavior in #10892 in a problematic way.
Previously, `Ready()` would create and immediately "accept" a Ready
(i.e. commit the app to actually handling it). In #10892, Ready() became
a pure read-only operation and the "accepting" was moved to
`Advance(rd)`. As a result it was illegal to use the RawNode in certain
ways while the Ready was being handled. Failure to do so would result in
dropped messages (and perhaps worse). For example, with the following
operations
1. `rd := rawNode.Ready()`
2. `rawNode.Step(someMsg)`
3. `rawNode.Advance(rd)`
`someMsg` would be dropped, because `Advance()` would clear out the
outgoing messages thinking that they had all been handled by the client.
I mistakenly assumed that this restriction had existed prior, but this
is incorrect.
I noticed this while trying to pick up the above PR in CockroachDB,
where it caused unit test failures, precisely due to the above example.
This PR reestablishes the previous behavior (result of `Ready()` must
be handled by the app) and adds a regression test.
While I was there, I carried out a few small clarifying refactors.
This change introduces joint quorums by changing the Node and RawNode
API to accept pb.ConfChangeV2 (on top of pb.ConfChange).
pb.ConfChange continues to work as today: it allows carrying out a
single configuration change. A pb.ConfChange proposal gets added to
the Raft log as such and is thus also observed by the app during Ready
handling, and fed back to ApplyConfChange.
ConfChangeV2 allows joint configuration changes but will continue to
carry out configuration changes in "one phase" (i.e. without ever
entering a joint config) when this is possible.
It has a data race between the test's call to `reduceUncommittedSize`
and a corresponding call during Ready handling in `(*node).run()`.
The corresponding RawNode test still verifies the functionality, so
instead of fixing the test we can remove it.
We are worried about breaking backwards compatibility for any
application out there that may have relied on the old behavior. Their
RawNode invocation would have been broken by the removal of the peers
argument so it would not have changed silently; an associated comment
tells callers how to fix it.
This is the first (maybe not last) step in cleaning up the bootstrap
code around StartNode.
Initializing a Raft group for the first time is awkward, since a
configuration has to be pulled from thin air. The way this is solved
today is unclean: The app is supposed to pass peers to StartNode(),
we add configuration changes for them to the log, immediately pretend
that they are applied, but actually leave them unapplied (to give the
app a chance to observe them, though if the app did decide to not apply
them things would really go off the rails), and then return control to
the app. The app will then process the initial Readys and as a result
the configuration will be persisted to disk; restarts of the node then
use RestartNode which doesn't take any peers.
The code that did this lived awkwardly in two places fairly deep down
the callstack, though it was really only necessary in StartNode(). This
commit refactors things to make this more obvious: only StartNode does
this dance now. In particular, RawNode does not support this at all any
more; it expects the app to set up its Storage correctly.
Future work may provide helpers to make this "preseeding" of the Storage
more user-friendly. It isn't entirely straightforward to do so since
the Storage interface doesn't provide the right accessors for this
purpose. Briefly speaking, we want to make sure that a non-bootstrapped
node can never catch up via the log so that we can implicitly use one
of the "skipped" log entries to represent the configuration change into
the bootstrap configuration. This is an invasive change that affects
all consumers of raft, and it is of lower urgency since the code (post
this commit) already encapsulates the complexity sufficiently.
It has always bugged me that any new feature essentially needed to be
tested twice due to the two ways in which apps can use raft (`*node` and
`*RawNode`). Due to upcoming testing work for joint consensus, now is a
good time to rectify this somewhat.
This commit removes most logic from `(*node).run` and uses `*RawNode`
internally. This simplifies the logic and also lead (via debugging) to
some insight on how the semantics of the approaches differ, which is now
documented in the comments.
Now that a Config is also added to the full status, the old name
did not convey the intention, which was to get a Status without
an associated allocation.
Recent refactoring to the String() method of `Progress` hit an NPE
because we return nil Inflights as part of the Raft status. Just
fix this at the source and properly populate the Raft status instead
of teaching String() to ignore nil. A real Progress always has a
non-nil Inflights.
This commit introduces machinery to safely apply joint consensus
configuration changes to Raft.
The main contribution is the new package, `confchange`, which offers
the primitives `Simple`, `EnterJoint`, and `LeaveJoint`.
The first two take a list of configuration changes. `Simple` only
declares success if these configuration changes (applied atomically)
change the set of voters by at most one (i.e. it's fine to add or
remove any number of learners, but change only one voter). `EnterJoint`
makes the configuration joint and then applies the changes to it, in
preparation of the caller returning later and transitioning out of the
joint config into the final desired configuration via `LeaveJoint()`.
This commit streamlines the conversion between voters and learners, which
is now generally allowed whenever the above conditions are upheld (i.e.
it's not possible to demote a voter and add a new voter in the context
of a Simple configuration change, but it is possible via EnterJoint).
Previously, we had the artificial restriction that a voter could not be
demoted to a learner, but had to be removed first.
Even though demoting a learner is generally less useful than promoting
a learner (the latter is used to catch up future voters), demotions
could see use in improved handling of temporary node unavailability,
where it is desired to remove voting power from a down node, but to
preserve its data should it return.
An additional change that was made in this commit is to prevent the use
of empty commit quorums, which was previously possible but for no good
reason; this:
Closes#10884.
The work left to do in a future PR is to actually expose joint
configurations to the applications using Raft. This will entail mostly
API design and the addition of suitable testing, which to be carried
out ergonomically is likely to motivate a larger refactor.
Touches #7625.
I had been dealing with these intermittent failures for a while and
finally figured out why. The real solution is making genproto.sh less
ugly but that won't happen for a while.
In order to cover message can well be received when a node is paused, this commit sends message async using goroutine and random sleep. This change makes recvms is possible to cache message during node.pause is triggered.
This run *should* certainly pass, but it's consistently the one that
fails with a regularity that essentially blocks the CI pipeline.
Someone needs to take a look at #10700, but in the meantime, the show
must go on.
Etcd currently supports validating peers based on their TLS certificate's
CN field. The current best practice for creation and validation of TLS
certs is to use the Subject Alternative Name (SAN) fields instead, so that
a certificate might be issued with a unique CN and its logical
identities in the SANs.
This commit extends the peer validation logic to use Go's
`(*"crypto/x509".Certificate).ValidateHostname` function for name
validation, which allows SANs to be used for peer access control.
In addition, it allows name validation to be enabled on clients as well.
This is used when running Etcd behind an authenticating proxy, or as
an internal component in a larger system (like a Kubernetes master).
Make it less verbose by omitting the values for the steady state.
Also rearrange the order so that information that is typically more
relevant is printed first.
At the time of writing, we don't allow configuration changes to change
voters to learners directly, but note that a snapshot may compress
multiple changes to the configuration into one: the voter could have
been removed, then readded as a learner and the snapshot reflects both
changes. In that case, a voter receives a snapshot telling it that it is
now a learner. In fact, the node has to accept that snapshot, or it is
permanently cut off from the Raft log.
I think this just wasn't realized in the original work, but this is just
my guess since there generally is very little rationale on the various
decisions made. I also generally haven't been able to figure out whether
the decision to prevent voters from becoming learners without first
having been removed was motivated by some particular concern, or if it
just wasn't deemed necessary. I suspect it is the latter because
demoting a voter seems perfectly safe.
See https://github.com/etcd-io/etcd/pull/8751#issuecomment-342028091.
This is helpful to quickly print the configuration log messages without
having to specify Voters and Learners separately.
It will also come in handy for joint quorums because it allows holding
on to voters and learners as a unit, which is useful for unit testing.
Put all the logic related to applying a configuration change in one
place in preparation for adding joint consensus.
This inspired various TODOs.
I had to rewrite TestSnapshotSucceedViaAppResp since it was relying
on a snapshot applied to the leader, which is now prevented.
Description: w.mu is locked at line 385 and unlocked at line 396. Among 5 return statements in this function, 4 are below line 396 but there is 1 return at line 387.
Fix: Add w.mu.Unlock() before that return at line 387.
Mechanically extract `progressTracker`, `Progress`, and `inflights`
to their own package named `tracker`. Add lots of comments in the
progress, and take the opportunity to rename and clarify various
fields.
Every other test build times out due to the 20 minute test timeout. I
doesn't seem like tests are actually hanging, it's more that 20 minutes
just isn't enough to run the tests any more.
To ease a future transition into joint quorums, this commit removes the
previous "ad-hoc" majority-based quorum and vote computations with that
introduced in the `raft/quorum` package.
More specifically, the progressTracker now uses a quorum.JointConfig for
which the "second" majority quorum is always empty; in this case the
quorum behaves like the one quorum.MajorityConfig that is actually
present. Or, more briefly, this change is a no-op, but it will take the
busywork out of actually starting to make use of joint quorums in the
future.
On a side node, I suspect that this might've fixed a bug regarding the
read index though I haven't been able to explicitly come up with a
counter-example. The problem was that the acks collected for the read
index weren't taking into account membership changes, so they'd run the
danger of using acks from nodes since removed to claim that a quorum of
acks had been received. There's a chance that there isn't a
counter-example (the only guarantee extracted from the "quorum" is that
there isn't another leader, but even if there's another leader all that
matters is that that leader doesn't have a divergent history from the
stale leader in the hypothetical counter-example), but either way there
is morally a bug here that is now fixed because VoteCommitted doesn't
care about votes from members that are not voters known to the currently
active configuration.
Instead of having disjoint mappings of ID to *Progress for voters and
learners, use a map[id]struct{} for each and share a map of *Progress
among them.
This is easier to handle when joint quorums are introduced, at which
point a node may be a voting member of two quorums.
The quorum package contains logic to reason about committed indexes as
well as vote outcomes for both majority and joint quorums. The package
is oblivious to the existence of learner replicas.
The plan is to hook this up to etcd/raft in subsequent commits.
We were already taking some precautions against learners campaigning,
but there was no safeguard against an explicit call to `Campaign()`.
The newly added test also verifies that leadership transfers to
learners are ignored.
This will keep them from diverging to much. In fact we should remove
some of the obvious differences that have crept in over time so that
what remains is structural. This isn't done in this commit since
it amounts to a change in the public API; we should lump this in
when we break the public API the next time.
Update to Go 1.12.5 testing. Remove deprecated unused and gosimple
pacakges, and mask staticcheck 1006. Also, fix unconvert errors related
to unnecessary type conversions and following staticcheck errors:
- remove redundant return statements
- use for range instead of for select
- use time.Since instead of time.Now().Sub
- omit comparison to bool constant
- replace T.Fatal and T.Fatalf in tests with T.Error and T.Fatalf respectively because the goroutine calls T.Fatal must be called in the same goroutine as the test
- fix error strings that should not be capitalized
- use sort.Strings(...) instead of sort.Sort(sort.StringSlice(...))
- use he status code of Canceled instead of grpc.ErrClientConnClosing which is deprecated
- use use status.Errorf instead of grpc.Errorf which is deprecated
Related #10528#10438
related: https://github.com/etcd-io/etcd/pull/10668
Provide a ref to the issue and PR management doc from the README,
similar to other references we have provided in the README.
This commit adds a feature for creating a user without password. The
purpose of the feature is reducing attack surface by configuring bad
passwords (CN based auth will be allowed for the user).
The feature can be used with `--no-password` of `etcdctl user add`
command.
Fix https://github.com/coreos/etcd/issues/9590
Update TestMemberPromote to include both learner not-ready and learner
ready test cases.
Removed unit test TestPromoteMember, it requires underlying raft node to
be started and running. The member promote is covered by the integration
test.
Be more explicit in document and command line usage message that if a
config file is provided, other command line flags and environment
variables will be ignored.
Improve readability of ETCD_CONFIG_FILE env variable parsing part
by adding comments and using flags.FlagToEnv function.
Signed-off-by: Andrey Abramov <st5pub@yandex.ru>
This doesn't completely eliminate access to prs.nodes, but that's not
really necessary. This commit uses the existing APIs in a few more
places where it's convenient, and also sprinkles some assertions.
The Progress maps contain both the active configuration and information
about the replication status. By pulling it into its own component, this
becomes easier to unit test and also clarifies the code, which will see
changes as etcd-io/etcd#7625 is addressed.
More functionality will move into `prs` in self-contained follow-up commits.
I no longer have the time to maintain etcd as my career takes me to a different direction; Hence, I think it is appropriate to remove myself from the maintainer responsibility.
Working on etcd project was one of the most challenging and rewarding experiences I ever had. Thanks @xiang90 @gyuho @heyitsanthony @philips
We may not want to suggest to contact CoreOS now. We could remove this
section but consiering the nature of the subject, discussion with the project
maintainers probably a good idea if someone doesn't find it comfortable
to report an issue right away.
Adding integration test TestTransferLeadershipWithLearner, which ensures
that TransferLeadership does not timeout due to learner is automatically
picked by leader as transferee.
1. Maintenance API MoveLeader() returns ErrBadLeaderTransferee if
transferee does not exist or is raft learner.
2. etcdserver TransferLeadership() only choose voting member as
transferee.
Added IsLearner field to etcdserver internal Member type. Routed
learner MemberAdd request from server API to raft. Apply learner
MemberAdd result to server after the request is passed through Raft.
- Added isLearner flag to MemberAddRequest in Cluster API.
- Added isLearner field to StatusResponse in Maintenance API.
- Added MemberPromote rpc to Cluster API.
I would like to propose a formal guide for issue triage and PR management.
This should help us keep open issues and PRs under a desirable numbers.
For example, keep issues under 100. These guidelines should specially help
manage and close issues and PRs that are inactive in a timely manner.
To remove the dependency on ghodss/yaml. Replaced this dependency with sigs.k8s.io/yaml.
This wil help to remove the ghodss/yaml dependency from main kubernetes repository.
xref: https://github.com/kubernetes/kubernetes/issues/77024
The documentation mentions fio as a tool to benchmark disks to assess
whether they are fast enough for etcd. But doing that is far from trivial,
because fio is very flexible and complex to use, and the user must make sure
that the workload fio generates mirrors the I/O workload of its etcd cluster
closely enough. This commit adds links to a blog post with an example of how
to do that.
Appending to an empty slice twice could (and often did) result in
multiple allocations. This was wasteful. We can avoid this by performing
a single allocation with the correct size and copying into it.
`raftpb.Entry.String` takes a pointer receiver, so calling it
on a loop variable was causing the variable to escape. Removing
the `.String()` call was enough to avoid the allocation, but
this also avoids a memory copy and prevents similar bugs.
This was responsible for 11.63% of total allocations in an
experiment with https://github.com/nvanbenschoten/raft-toy.
By boxing a heap-allocated slice header instead of the slice
header on the stack, we can avoid an allocation when passing
through the sort.Interface interface.
This was responsible for 26.61% of total allocations in an
experiment with https://github.com/nvanbenschoten/raft-toy.
This PR resolves an issue where the `/metrics` endpoints exposed by the proxy were not returning metrics of the etcd members servers but of the proxy itself.
Signed-off-by: Sam Batschelet <sbatsche@redhat.com>
Add a bunch of tests on fundamental operation of Create/Set/Delete.
Context: I want to use this package to run the discovery service against
the v3 storage backend. The limited functionality already implemented
should be sufficient to do this.
https://github.com/coreos/discovery.etcd.io/issues/52
Leader should check message sender after receiving MsgReadIndex, even
when raft quorum is 1. The message could be sent from learner node, and
leader should respond.
When using the embed package to embed etcd, sometimes the storage prefix
being used might be full. In this case, this code path triggers, causing
an: `etcdserver: create wal error: no space left on device` error, which
causes a fatal. A fatal differs from a panic in that it also calls
os.Exit(1). In this situation, the calling program that embeds the etcd
server will be abruptly killed, which prevents it from cleaning up
safely, and giving a proper error message. Depending on what the calling
program is, this can cause corruption and data loss.
This patch switches the fatal to a panic. Ideally this would be a
regular error which would get propagated upwards to the StartEtcd
command, but in the meantime at least this can be caught with recover().
This fixes the most common fatal that I've experienced, but there are
surely more that need looking into. If possible, the errors should be
threaded down into the code path so that embedding etcd can be more
robust.
Fixes: https://github.com/etcd-io/etcd/issues/10588
Add documentation to clarify that when writing TXN commands, multi-line values should be written using "\n" and not a literal newline (as in other commands).
Fixes#10169
Closing of watch by client will cancel the watch grpc stream and
can produce a context canceled error. However, since client
simply wanted to close the watcher the error can create confusion
that something went wrong instead of a successful close. Ensure
that Close do not return error.
Fixed#10340
Currently, when we access the URL https://www.grpc.io, it is redirected to https://www.grpc.io automatically.
So this commit aims to replace **HTTP** to **HTTPs** for security.
Currently alert messages state that we detect issue
within the last 1 hour, although we check
for last 15min and wait for 15min for this alert to keep firing.
This fix changes the message to be 30minutes.
This commit lets grpc gateway return a correct error to clients.
Even if a client has a cert with non empty CN, current gateway returns
an error like below:
```
$ curl --cacert ./integration/fixtures/ca.crt --cert ./integration/fixtures/server.crt --key ./integration/fixtures/server.key.insecure https://localhost:2379/v3/kv/put -X POST -d '{"key": "fromcurl", "value": "test"}'
{"error":"etcdserver: user name is empty","code":3}
```
This is because etcd ignores CN from gateway connection.
The error will be like this:
```
$ curl --cacert ./integration/fixtures/ca.crt --cert ./integration/fixtures/server.crt --key ./integration/fixtures/server.key.insecure https://localhost:2379/v3/kv/put -X POST -d '{"key": "fromcurl", "value": "test"}'
CommonName of client sending a request against gateway will be ignored and not used as expected
```
The error will be returned if the server is enabling auth and gRPC
gateway.
Don't panic if command is given in interactive mode, give a nice error
message instead.
Before:
$ ./bin/etcdctl watch -i
<hit return>
panic: runtime error: index out of range
goroutine 1 [running]:
etcdctl/ctlv3/command.watchInteractiveFunc(...)
etcd/etcdctl/ctlv3/command/watch_command.go:104 ...
After:
$ ./bin/etcdctl watch -i
<hit return>
Invalid command: (watch and progress supported)
foo
Invalid command foo (only support watch)
The documentation recommends using `etcdctl` to verify that etcd has
been built correctly, but the `go get` command provided does not install
it. This changes it so that it does, and also clarifies terminology
('using `go get`', referring to the command used to install it, rather
than 'using `$GOPATH`').
When a follower requires a snapshot and the snapshot is sent at the
committed (and last) index in an otherwise idle Raft group, the follower
would previously remain in ProgressStateProbe even though it had been
caught up completely.
In a busy Raft group this wouldn't be an issue since the next round of
MsgApp would update the state, but in an idle group there's nothing
that rectifies the status (since there's nothing to append or update).
The reason this matters is that the state is exposed through
`RaftStatus()`. Concretely, in CockroachDB, we use the Raft status to
make sharding decisions (since it's dangerous to make rapid changes
to a fragile Raft group), and had to work around this problem[1].
[1]: 91b11dae41/pkg/storage/split_delay_helper.go (L138-L141)
The leader perpetually kept itself in ProgressStateProbe even though of
course it has perfect knowledge of its log. This wasn't usually an issue
because it also doesn't care about its own Progress, but it's better to
keep this data correctly maintained, especially since this is part of
raft.Status and thus becomes visible to applications using the Raft
library.
(Concretely, in CockroachDB we use the Progress to inform log
truncations).
Prior to this change, MaxSizePerMsg was used both to cap the total byte size of
entries in messages as well as the total byte size of entries passed through
CommittedEntries in the Ready struct. This change adds a new Config parameter
MaxCommittedSizePerReady which defaults to MaxSizePerMsg and contols the second
of above descibed settings.
Once chk(ai) fails with auth.ErrAuthOldRevision it will always do,
regardless how many times you retry. So the error is better be returned
to fail the pending request and make the client re-authenticate.
etcd currently generates a few UUID style identifiers using approaches like `fmt.Sprintf("client-%s", strconv.FormatInt(time.Now().UnixNano(), 36))`.
But these can collide on machine architectures with larger timestamp steps (see https://github.com/etcd-io/etcd/issues/10035).
The previous code was using the proto-generated `Size()` method to
track the size of an incoming proposal at the leader. This includes
the Index and Term, which were mutated after the call to `Size()`
when appending to the log. Additionally, it was not taking into
account that an ignored configuration change would ignore the
original proposal and append an empty entry instead.
As a result, a fully committed Raft group could end up with a non-
zero tracked uncommitted Raft log counter that would eventually hit
the ceiling and drop all future proposals indiscriminately. It would
also immediately imply that proposals exceeding the threshold alone
would get refused (as the "first uncommitted proposal" gets special
treatment and is always allowed in).
Track only the size of the payload actually appended to the Raft log
instead.
For context, see:
https://github.com/cockroachdb/cockroach/issues/31618#issuecomment-431374938
Currently the EtcdInsufficientMembers alert fires, when more than (X/2)-1
instances are unavailable. This fixes it to fire at the correct limit of (X-1)/2
unavailable instances and $value now contains the number of available instances
instead of unavailable ones. Added unit test for EtcdInsufficientMembers alert.
The suggested pattern for Raft proposals is that they be retried
periodically until they succeed. This turns out to be an issue
when a leader cannot commit entries because the leader will continue
to append re-proposed entries to its log without committing anything.
This can result in the uncommitted tail of a leader's log growing
without bound until it is able to commit entries.
This change add a safeguard to protect against this case where a
leader's log can grow without bound during loss of quorum scenarios.
It does so by introducing a new, optional ``MaxUncommittedEntriesSize
configuration. This config limits the max aggregate size of uncommitted
entries that may be appended to a leader's log. Once this limit
is exceeded, proposals will begin to return ErrProposalDropped
errors.
See cockroachdb/cockroach#27772
This PR adds another probing routine to monitor the connection
for Raft message transports. Previously, we only monitored
snapshot transports.
In our production cluster, we found one TCP connection had >8-sec
latencies to a remote peer, but "etcd_network_peer_round_trip_time_seconds"
metrics shows <1-sec latency distribution, which means etcd server
was not sampling enough while such latency spikes happen
outside of snapshot pipeline connection.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
Convenient invariant:
- if werr == nil then lock is supposed to be locked at the moment.
While we could not be confident in stronger invariant ('is exactly locked'),
it were inconvenient that previous code could return `werr == nil` after
Mutex.Unlock.
It could happen when ctx is canceled/timeouted exactly after waitDeletes
successfully returned werr == nil and before `<-ctx.Done()` checked.
While such situation is very rare, it is still possible.
fixes#10111
We should allow etcd client use all of the available keepalive
client parameters as documented in this link,
https://godoc.org/google.golang.org/grpc/keepalive#ClientParameters
Currently in the etcd, by default PermitWithoutStream is set to
false, and user has no way to override it.
On the server side, we explicitely setting EnforcementPolicy
PermitWithoutStream to false and don't provide option to override it
to user but on the client side we should allow this option as
provided by the grpc.
When building tools on Win,it shows `.\main.go:68:12: assignment mismatch: 2 variables but 1 values`.The reason is the return variables not match the calling from `main.go` and i try to fix it.
Maintain existing error message for not-enough-args
Add "too many args" if too many args
Add more helpful error message if v2 syntax was used
New output:
```
sauer@host:~/dev/etcd$ ./bin/etcdctl --endpoints http://localhost:5001 member add
Error: member name not provided.
sauer@host:~/dev/etcd$ ./bin/etcdctl --endpoints http://localhost:5001 member add node2 node2
Error: too many arguments
sauer@host:~/dev/etcd$ ./bin/etcdctl --endpoints http://localhost:5001 member add node2 http://localhost:6002
Error: too many arguments, did you mean "--peer-urls http://localhost:6002"
sauer@host:~/dev/etcd$ ./bin/etcdctl --endpoints http://localhost:5001 member add http://localhost:6002 node2
Error: too many arguments, did you mean "--peer-urls http://localhost:6002"
```
The previous logic was erroneously setting Ready.MustSync to true when
the hard state had not changed because we were comparing an empty hard
state to the previous hard state. In combination with another misfeature
in CockroachDB (unnecessary writing of empty batches), this was causing
a steady stream of synchronous writes to disk.
In #9982, a mechanism to limit the size of `CommittedEntries` was
introduced. The way this mechanism worked was that it would load
applicable entries (passing the max size hint) and would emit a
`HardState` whose commit index was truncated to match the limitation
applied to the entries. Unfortunately, this was subtly incorrect
when the user-provided `Entries` implementation didn't exactly
match what Raft uses internally. Depending on whether a `Node` or
a `RawNode` was used, this would either lead to regressing the
HardState's commit index or outright forgetting to apply entries,
respectively.
Asking implementers to precisely match the Raft size limitation
semantics was considered but looks like a bad idea as it puts
correctness squarely in the hands of downstream users. Instead, this
PR removes the truncation of `HardState` when limiting is active
and tracks the applied index separately. This removes the old
paradigm (that the previous code tried to work around) that the
client will always apply all the way to the commit index, which
isn't true when commit entries are paginated.
See [1] for more on the discovery of this bug (CockroachDB's
implementation of `Entries` returns one more entry than Raft's when the
size limit hits).
[1]: https://github.com/cockroachdb/cockroach/issues/28918#issuecomment-418174448
Go 1.11 now marks len(channel) over being-closed channel
as racey operation, fix tests by receiving from channel first
and then check the length of channel.
```
WARNING: DATA RACE
Write at 0x00c000e872c0 by goroutine 198:
runtime.closechan()
/usr/local/go/src/runtime/chan.go:327 +0x0
go.etcd.io/etcd/clientv3.(*lessor).closeRequireLeader()
/Users/leegyuho/go/src/go.etcd.io/etcd/clientv3/lease.go:379 +0x748
go.etcd.io/etcd/clientv3.(*lessor).recvKeepAliveLoop()
/Users/leegyuho/go/src/go.etcd.io/etcd/clientv3/lease.go:455 +0x3a5
Previous read at 0x00c000e872c0 by goroutine 27:
go.etcd.io/etcd/clientv3/integration.TestLeaseWithRequireLeader()
/Users/leegyuho/go/src/go.etcd.io/etcd/clientv3/integration/lease_test.go:828 +0x810
testing.tRunner()
/usr/local/go/src/testing/testing.go:827 +0x162
```
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
Several RPC references in README with memberlist only hyperlinked,
and since it's linked with line numbers it's not pointing to a
desired ref now. Remove the link to make it consistent and correct.
"read index" doesn't tell much about the root cause.
Most likely, the local follower node is having slow
network, thus timing out waiting to receive read
index response from leader.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
This change allows Watch users to retrieve the cancel reason when a
watch is canceled by the server. Additionally WatchResponses with
closeErr set now have Canceled set true which is in line with the
documentation for the Canceled field.
Now returns errors from checkPermissionForWatch() via the CancelReason
field. This allows clients to understand why the watch was canceled.
Additionally, this change protects a watch from starting and that
otherwise might hang indefinitely.
Both "client-transport-security" and "peer-transport-security"
is mapped to Go struct embed.securityConfig.
Field for client certificate authentication is tagged as
"client-cert-auth", but it is misspelled in "peer-transport-security"
section.
Distribution would be:
0.1 second or more
...
25.6 seconds or more
51.2 seconds or more
etcd_network_snapshot_send_success
etcd_network_snapshot_send_failures
etcd_network_snapshot_send_total_duration_seconds
etcd_network_snapshot_receive_success
etcd_network_snapshot_receive_failures
etcd_network_snapshot_receive_total_duration_seconds
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
```
etcd_server_id{server_id="8e9e05c52164694d"} 1
```
Useful for automating membership change operations,
no need to run "endpoint status" or "member list"
command to get member IDs.
Also, useful for "etcd_network" metrics with "To/From" labels.
Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
The benchmark as a sub command of put when provided will fetch hashkv and checks
the time taken to get it.
Fixed # 8910
Provider a way to etcd user to check how long it takes to get
hashkv in user enviornment. The command ouput will provide time taken
to get hashkv along with db file size.
etcd server
To improve debuggability of etcd v3. Added a grpc interceptor to log
info on incoming requests to etcd server. The log output includes
remote client info, request content (with value field redacted), request
handling latency, response size, etc. Uses zap logger if available,
otherwise uses capnslog.
Also did some clean up on the chaining of grpc interceptors on server
side.
We allow multiple in-flight append messages, but prior to this change
the only way we'd ever send them is if there is a steady stream of new
proposals. Catching up a follower that is far behind would be
unnecessarily slow (this is exacerbated by a quirk of CockroachDB's
use of raft which limits our ability to catch up via snapshot in some
cases).
See cockroachdb/cockroach#27983
The MaxSizePerMsg setting is now used to limit the size of
Ready.CommittedEntries. This prevents out-of-memory errors if the raft
log has become very large and commits all at once.
Since syscall.Errno implements net.Error and all cases
are matched sequentially, it's a mistake to put syscall.Errno
case after net.Error since it will never be executed.
This change swaps syscall.Errno case with net.Error
to give that clause chance to execute.
Joe has been helping fix lots of bugs and involved
in critical feature design/implementation,
plus leading patch release process for over a year.
Thanks for your excellent work.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
The error message is different to the condition it checks for. This PR
modifies the error message accordingly.
Closes#9717.
Signed-off-by: Kostas Christidis <kostas@christidis.io>
client should update next keepalive send time
even when lease keepalive response queue becomes full.
Otherwise, client sends keepalive request every 500ms
regardless of TTL when the send is only expected to happen
with the interval of TTL / 3 at minimum.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
gRPC has moved the transport package to an internal-only directory. This
eliminates direct use of the transport package in the stress test in
favor of the error code from gRPC that represents a connection problem.
https://godoc.org/google.golang.org/grpc/internal/transport is the new
location for the package, which says it's not intended to be imported
directly. Instead, the maintainers suggested to use the code Unavailable
to detect a connection problem.
This change slightly reorganizes the stresser test error handling.
The HTTP metrics have been deprecated and removed. In other places all
the HTTP related alerts have already been removed, this is just a clean
up of the remaining places these were left.
Using SRV discovery with TLS, the SRV record must be in the DNS SAN or clustering will fail.
This is a new requirement and may cause mysterious failures when upgrading from 3.1 to 3.2. I was only able to fix this in our configuration after reading through #8445; and now I understand the problem it's clear the docs have a hole here.
mirror_maker doc mentioned "Data under the destination cluster’s mirroring prefix should be treated as read only."
To avoid confusion, read only is being removed and a clear statement mentions that the updated values at destination wont be replicated from destination to origin.
wont -> won't
Fix
=== RUN TestEmbedEtcd
==================
WARNING: DATA RACE
Write at 0x000001df86d0 by goroutine 711:
github.com/coreos/etcd/embed.(*Config).setupLogging.func1()
/go/src/github.com/coreos/etcd/vendor/google.golang.org/grpc/grpclog/loggerv2.go:68 +0x16c
sync.(*Once).Do()
/usr/local/go/src/sync/once.go:44 +0xe1
github.com/coreos/etcd/embed.(*Config).setupLogging()
in gRPC proxy tests.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
"# github.com/coreos/etcd/raft
raft/logger.go:117: missing ... in args forwarded to print-like function"
New parameter check got added the golang to check the function parameter
c006036075 (diff-8fa5b0d6191706747ef5773f895781c9)
We only get 5 concurrent workers in Travis.
Save time by fetching test image only once
for all build tests.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Because the leases were sorted inside UnsafeLeases() the lessor mutex
ended up being locked while the whole map was sorted. This pulls the
soring outside of the lock, per feedback on
https://github.com/coreos/etcd/pull/9699
This also happens without gRPC proxy.
Fix panic when gRPC proxy leader watcher is restored:
```
go test -v -tags cluster_proxy -cpu 4 -race -run TestV3WatchRestoreSnapshotUnsync
=== RUN TestV3WatchRestoreSnapshotUnsync
panic: watcher minimum revision 9223372036854775805 should not exceed current revision 16
goroutine 156 [running]:
github.com/coreos/etcd/mvcc.(*watcherGroup).chooseAll(0xc4202b8720, 0x10, 0xffffffffffffffff, 0x1)
/home/gyuho/go/src/github.com/coreos/etcd/mvcc/watcher_group.go:242 +0x3b5
github.com/coreos/etcd/mvcc.(*watcherGroup).choose(0xc4202b8720, 0x200, 0x10, 0xffffffffffffffff, 0xc420253378, 0xc420253378)
/home/gyuho/go/src/github.com/coreos/etcd/mvcc/watcher_group.go:225 +0x289
github.com/coreos/etcd/mvcc.(*watchableStore).syncWatchers(0xc4202b86e0, 0x0)
/home/gyuho/go/src/github.com/coreos/etcd/mvcc/watchable_store.go:340 +0x237
github.com/coreos/etcd/mvcc.(*watchableStore).syncWatchersLoop(0xc4202b86e0)
/home/gyuho/go/src/github.com/coreos/etcd/mvcc/watchable_store.go:214 +0x280
created by github.com/coreos/etcd/mvcc.newWatchableStore
/home/gyuho/go/src/github.com/coreos/etcd/mvcc/watchable_store.go:90 +0x477
exit status 2
FAIL github.com/coreos/etcd/integration 2.551s
```
gRPC proxy spawns a watcher with a key "proxy-namespace__lostleader"
and watch revision "int64(math.MaxInt64 - 2)" to detect leader loss.
But, when the partitioned node restores, this watcher triggers
panic with "watcher minimum revision ... should not exceed current ...".
This check was added a long time ago, by my PR, when there was no gRPC proxy:
https://github.com/coreos/etcd/pull/4043#discussion_r48457145
> we can remove this checking actually. it is impossible for a unsynced watching to have a future rev. or we should just panic here.
However, now it's possible that a unsynced watcher has a future
revision, when it was moved from a synced watcher group through
restore operation.
This PR adds "restore" flag to indicate that a watcher was moved
from the synced watcher group with restore operation. Otherwise,
the watcher with future revision in an unsynced watcher group
would still panic.
Example logs with future revision watcher from restore operation:
```
{"level":"info","ts":1527196358.9057755,"caller":"mvcc/watcher_group.go:261","msg":"choosing future revision watcher from restore operation","watch-key":"proxy-namespace__lostleader","watch-revision":9223372036854775805,"current-revision":16}
{"level":"info","ts":1527196358.910349,"caller":"mvcc/watcher_group.go:261","msg":"choosing future revision watcher from restore operation","watch-key":"proxy-namespace__lostleader","watch-revision":9223372036854775805,"current-revision":16}
```
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
{"level":"warn","ts":1527101858.6985068,"caller":"etcdserver/util.go:115","msg":"apply request took too long","took":0.114101529,"expected-duration":0.1,"prefix":"","request":"header:<ID:1029181977902852337> put:<key:\"\\000\\000...
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
{"level":"warn","ts":1527101858.4149103,"caller":"etcdserver/raft.go:370","msg":"failed to send out heartbeat; took too long, server is overloaded likely from slow disk","heartbeat-interval":0.1,"expected-duration":0.2,"exceeded-duration":0.025771662}
{"level":"warn","ts":1527101858.4149644,"caller":"etcdserver/raft.go:370","msg":"failed to send out heartbeat; took too long, server is overloaded likely from slow disk","heartbeat-interval":0.1,"expected-duration":0.2,"exceeded-duration":0.034015766}
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
This commit adds two flags to etcdctl:
1. `--password` flag to etcdctl as a global option. It can be used for
specifying password for authentication required for the command
execution.
2. `--new-user-password` flag to `etcdctl user add`. It can be used
for specifying password of newly created user by the command.
The main motivation of the flags is allowing user to have : in its
name.
Fix https://github.com/coreos/etcd/issues/9691
systemd/journal should be configured manually.
Interpreting PPID 1 as systemd unit is wrong,
especially when embedded etcd runs under Docker
container. For such case, every single log write
will error and fall back to stderr, which is
inefficient.
Instead, add "systemd/journal" log output option
and returns error if systemd/journal socket cannot
be found.
"--logger=zap --log-outputs=default" will only error
for v3.4, since zap logger is still experimental.
v3.5 deprecates capnslog and changes "--log-outputs"
default value to "--log-outputs=stderr".
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
We replace/insert into in-memory B-tree, which means
we only keep a single node per key thus do not support
delete by revision on B-tree. So, (*keyIndex).tombstone
has always been marked with latest revision.
tombstone with key's modified revision panics:
panic: store.keyindex: put with unexpected smaller revision [{2 0} / {2 0}]
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
The `--listen-metrics-urls` also responds to the `/health` endpoint, but
that was not made clear in the documentation. These updates should help
explain how else that flag can be used.
When a new file is created under an non existent directly,
the v2 API automatically create the parent directly.
This commit aligns the behaviour of v2v3 emulation to comply with the v2
API.
"--log-output default,a.log" should error out when etcd
runs as a systemd unit. We expect 'default' to be overridden
explicitly.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
For compaction, clone the original Btree for traversal purposes, so as to
not hold the lock for the duration of compaction. This allows read/write
throughput by not blocking when the index tree is large (> 1M entries).
mvcc: add comment for index compaction lock
mvcc: explicitly unlock store to do index compaction synchronously
mvcc: formatting index bench
mvcc: add release note for index compaction changes
mvcc: add license header
- Add/Document "logger" to support structured logging.
- This makes functional tests run easier, since zap logger
provides built-in log redirect to files.
- "etcd --logger-option=zap" to enable structured logging.
- Current "capnslog" will still be used as "default".
- We may switch the default or deprecate "capnslog" in v3.5.
- Either way, will clearly be documented.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Balancer tests have been flaky since last balancer rewrite.
Should be from slow balancer failover. Once we re-rewrite balancer
with roundrobin, there should be no more flaky tests as below:
TestBalancerUnderServerStopInflightLinearizableGetOnRestart (27.62s)
server_shutdown_test.go:343: context deadline exceeded
TestBalancerUnderServerShutdownDelete (3.22s)
util.go:32: context deadline exceeded
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Since heap is already sorted, we can just check first element
to see if anything is expiry, rather than popping and pushing
it back. If nothing is expiry, pop operation is unnecessary.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
This adds a heap acting as a priority queue to keep track of lease
exiprations. Previously the whole lease map had to be iterated through
each time.
The queue allows us to check only those leases which might be expired.
When the expiration changes, we add an additional entry. If we check an
entry that isn't expired, it means that the lease got extended.
If we find a entry in the heap that doesn't have a corresponding entry in
the map, we know that the lease has already been expired or revoked.
Tests in `rafttest` would fail because they referred to field `Id` instead of
`ID`. This PR fixes that.
Closes#9504.
Signed-off-by: Kostas Christidis <kostas@christidis.io>
This confused me just looking at the protos; reading up on coreos/etcd#6518 helped clarify things. I highlighted the terms that show up as fields in protos and tried to clean up some of the language.
Current etcd code uses the string literals ("token", "authorization")
as field names of grpc and swappger metadata for passing token. It is
difficult to maintain so this commit introduces new constants for the
purpose.
Now Restart takes longer, and leasing Get blocks
on server restarts anyway, so fix CI failures in
slow machines.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Prometheus that scrapes etcd might also scrape other things, so we should
specifically ask for etcd metrics, especially when dealing with generic
metrics like `process_resident_memory_bytes`.
This commit adds a new option of --auth-token, ttl, for configuring
TTL of jwt tokens. It can be specified like this:
```
--auth-token jwt,pub-key=<pub key path>,priv-key=<priv key path>,sign-method=<sign method>,ttl=5m
```
In the above case, TTL will be 5 minutes.
This commit adds a new auth token provider named nop. The nop provider
refuses every Authenticate() request so CN based authentication can
only be allowed. If the tokenOpts parameter of auth.NewTokenProvider()
is empty, the provider will be used.
"ActiveSince" is read-only, and should be able to call
concurrently, as long as there is no routine holding
write lock (send, send snapshot).
e.g. "ActiveSince" is used around etcd server
"processInternalRaftRequestOnce", should be non-blocking
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Running check datascale can create large history of keyspaces and
internal fragmentation. Allow user to run auto compact and defrag
when run check datascale.
I noticed that the docs mention the grpc proxy will listen on port 8080,
but the above example is explicitly telling it to listen on 2379.
Removing confusion.
We enable "raft.Config.CheckQuorum" by default in other
Raft initial starts. So should start with "ForceNewCluster".
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
"stepCandidate" should reuse candidate's own term, not term in Message,
because pre-vote is requested with future term.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
`raft.Step` already ensures that when `m.Term > r.Term`,
candidate reverts back to follower with its term being
reset with `m.Term`, thus it's always true that
`m.Term == r.Term` in `stepCandidate`.
This just makes `r.becomeFollower` calls consistent.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Create a new command similar to check perf that can check the memory
consumption for putting different workloads on a given endpoint. If no endpoint
is provided, localhost will be used. Return user with a message that whether
there are enough memory for a given workload with pass or fail.
Fixed#9121
Due to boltdb behavior, dbSizeInUse can be unequal to dbSize even when
dbSize is growing in some conditions. The possible gap between the sizes
is up to a couple of pages.
Closes#9302
Fix govet warnings with Go tip
```
tools/etcd-test-proxy/main.go:47: Fprintln arg list ends with redundant
newline
```
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
In case syncWatchersLoop() starts before Restore() is called,
watchers already added by that moment are moved to s.synced by the loop.
However, there is a broken logic that moves watchers from s.synced
to s.uncyned without setting keyWatchers of the watcherGroup.
Eventually syncWatchers() fails to pickup those watchers from s.unsynced
and no events are sent to the watchers, because newWatcherBatch() called
in the function uses wg.watcherSetByKey() internally that requires
a proper keyWatchers value.
Membership reconfiguration may not be applied
when the new member joins. Also pass all endpoints
to check restore data in case of leader election or
network faults.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Existing dbSize shows physically allocated DB size and the backend
(boltdb) won't shrink it after a compaction until a user runs the defrag command.
The new dbSizeInUse shows the DB size that excludes free pages created
by compactions so that users can see the actual DB usage. dbSize >=
dbSizeInUse is always true.
Note that dbSizeInUse shows a page-based size and not byte level usage.
Reproducible builds are already done via Gopkg.lock.
Remove "constraint"s for external projects with conflicting
dependencies.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
This includes one theoretical logic change: A node that knows the
leader of the current term will no longer grant votes, even if it has
not yet voted in this term. It also adds a `m.Type == MsgPreVote`
guard on the `m.Term > r.Term` check, which was previously thought to
be incorrect (see #8517) but was actually just unclear.
Closes#8517Closes#8571
Large key writes (stressEntries[1].weight) should not take this
much weight. It was triggering "database size exceeded" errors.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Current etcdctl endpoint health --cluster asks password twice if auth
is enabled. This is because the command creates two client instances:
one for the purpose of checking endpoint health and another for
getting cluster members with MemberList(). The latter client doesn't
need to be authenticated because MemberList() is a public RPC. This
commit makes the client with no authed one.
Fix https://github.com/coreos/etcd/issues/9094
status.FromError can return nil, false. We are handling the return values
most places in code but some places we aren't. Fixing it herewith.
Fixes#9117
The context error with cancel code is typically for user cancellation which
should be at debug level. For other error codes we should display a warning.
Fixes#9085
As README declares in the beginning, flags can have dash and it should be
replaced with underscore while using. Also flags or commands are emphasized
in general. The range-end is not a flag or valid doc word and should not be
used as such.
bufio.NewReader.ReadString blocks even
when the process received syscall.SIGKILL.
Remove ptyMu mutex and make ReadString return
when *os.File is closed.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
This allows for watchers to be created concurrently
without needing potentially complex and latency-adding
queuing on the client.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Scanning the uncommitted portion of the raft log to determine whether
there are any pending config changes can be expensive. In
cockroachdb/cockroach#18601, we've seen that a new leader can spend so
much time scanning its log post-election that it fails to send
its first heartbeats in time to prevent a second election from
starting immediately.
Instead of tracking whether a pending config change exists with a
boolean, this commit tracks the latest log index at which a pending
config change *could* exist. This is a less expensive solution to
the problem, and the impact of false positives should be minimal since
a newly-elected leader should be able to quickly commit the tail of
its log.
Adding information that when config file is used other command line flags
and env variables will be ignored. This changes are a follow up of a
disucssion under PR,
https://github.com/coreos/etcd/pull/9066
It was getting revisions with "atRev==0", which makes
"available" from "keep" method always empty since
"walk" on "keyIndex" only returns true.
"available" should be populated with all revisions to be
kept if the compaction happens with the given revision.
But, "available" was being empty when "kvindex.Keep(0)"
since it's always the case that "rev.main > atRev==0".
Fix https://github.com/coreos/etcd/issues/9022.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
"WithRoot" is only used within local node, and
"AuthInfoFromCtx" expects token from incoming context.
Embed token with "NewIncomingContext" so that token
can be found in "AuthInfoFromCtx".
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
ftruncate changes st_blocks, and following fallocate
syscalls would return EINVAL when allocated block size
is already greater than requested block size
(e.g. st_blocks==8, requested blocks are 2).
Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>
The current Running etcd section only shows how to run etcd for installation
with master branch. If user has installed a pre-built release following the
instructions on the release page, the ./bin/etcd won't work to bring up the
etcd. The Getting etcd section covers both, pre-built and master branch,
with recommendation of pre-built usage so the Running etcd section is updated
accordingly.
fix#9003
There's already a section called "Server upgrade checklists" below.
Instead, highlight the listen URLs change as a breaking change in
server. Also update 3.2 and 3.3 gRPC requirements as v1.7.4.
Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
Test all possible cases of server shutdown with inflight range requests.
Removed redundant tests in kv_test.go.
Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>
Tests with cluster_proxy tags were failing, since isServerCtxTimeout
was defined with "+build !cluster_proxy".
Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>
Due to clock drifts in server-side, client context times out
first in server-side, while original client-side context is
not timed out yet.
Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>
etcdserver: only compare hash values if any
It's possible that peer has higher revision than local node.
In such case, hashes will still be different on requested
revision, but peer's header revision is greater.
etcdserver: count mismatch only when compact revisions are same
Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>
A good bug report has some very specific qualities, so please read over our short document on [reporting bugs][report_bugs] before submitting a bug report.
SSH into the instance, and install the github action self-hosted runner (see [install scripts](https://github.com/etcd-io/etcd/settings/actions/runners/new?arch=arm64&os=linux)).
### Step 3. Configure github action on the host
SSH into the instance, and configure the github action self-hosted runner.
First, we need disable ICU install (see [actions/runner issue on ARM64](https://github.com/actions/runner/issues/629)):
See [code changes](https://github.com/coreos/etcd/compare/v3.2.9...v3.2.10).
### Fixed
- Replace backend key-value database `boltdb/bolt` with [`coreos/bbolt`](https://github.com/coreos/bbolt/releases) to address [backend database size issue](https://github.com/coreos/etcd/issues/8009)
- Fix clientv3 balancer to handle [network partition](https://github.com/coreos/etcd/issues/8711)
- Upgrade [`google.golang.org/grpc`](https://github.com/grpc/grpc-go/releases) v1.2.1 to v1.7.3
- Upgrade [`github.com/grpc-ecosystem/grpc-gateway`](https://github.com/grpc-ecosystem/grpc-gateway/releases) v1.2 to v1.3
- Revert [discovery SRV auth `ServerName` with `*.{ROOT_DOMAIN}`](https://github.com/coreos/etcd/pull/8651) to support non-wildcard subject alternative names in the certs (see [issue #8445](https://github.com/coreos/etcd/issues/8445) for more contexts)
- For instance, `etcd --discovery-srv=etcd.local` will only authenticate peers/clients when the provided certs have root domain `etcd.local` (**not `*.etcd.local`**) as an entry in Subject Alternative Name (SAN) field
See [code changes](https://github.com/coreos/etcd/compare/v3.2.8...v3.2.9).
### Fixed(Security)
- Compile with [Go 1.8.4](https://groups.google.com/d/msg/golang-nuts/sHfMg4gZNps/a-HDgDDDAAAJ)
- Update `golang.org/x/crypto/bcrypt` (See [golang/crypto@6c586e1](https://github.com/golang/crypto/commit/6c586e17d90a7d08bbbc4069984180dce3b04117) for more)
- Fix discovery SRV bootstrapping to [authenticate `ServerName` with `*.{ROOT_DOMAIN}`](https://github.com/coreos/etcd/pull/8651), in order to support sub-domain wildcard matching (see [issue #8445](https://github.com/coreos/etcd/issues/8445) for more contexts)
- For instance, `etcd --discovery-srv=etcd.local` will only authenticate peers/clients when the provided certs have root domain `*.etcd.local` as an entry in Subject Alternative Name (SAN) field
- Automatic leadership transfer when leader steps down
- etcd flags
-`--strict-reconfig-check` flag is set by default
- Add `--log-output` flag
- Add `--metrics` flag
- v3 client
- Add SetEndpoints method; update endpoints at runtime
- Add Sync method; auto-update endpoints at runtime
- Add Lease TimeToLive API; fetch lease information
- replace Config.Logger field with global logger
- Get API responses are sorted in ascending order by default
- v3 etcdctl
- Add lease timetolive command
- Add `--print-value-only` flag to get command
- Add `--dest-prefix` flag to make-mirror command
- command get responses are sorted in ascending order by default
-`recipes` now conform to sessions defined in clientv3/concurrency
- ACI has symlinks to `/usr/local/bin/etcd*`
- experimental gRPC proxy feature
### Changed
- Deprecated following gRPC metrics in favor of [go-grpc-prometheus](https://github.com/grpc-ecosystem/go-grpc-prometheus):
-`etcd_grpc_requests_total`
-`etcd_grpc_requests_failed_total`
-`etcd_grpc_active_streams`
-`etcd_grpc_unary_requests_duration_seconds`
- etcd uses default route IP if advertise URL is not given
- Cluster rejects removing members if quorum will be lost
- SRV records (e.g., infra1.example.com) must match the discovery domain (i.e., example.com) if no custom certificate authority is given
- TLSConfig ServerName is ignored with user-provided certificates for backwards compatibility; to be deprecated in 3.2
- For example, `etcd --discovery-srv=example.com` will only authenticate peers/clients when the provided certs have root domain `example.com` as an entry in Subject Alternative Name (SAN) field
- Discovery now has upper limit for waiting on retries
- Warn on binding listeners through domain names; to be deprecated in 3.2
@ -14,17 +15,17 @@ etcd is Apache 2.0 licensed and accepts contributions via GitHub pull requests.
## Reporting bugs and creating issues
Reporting bugs is one of the best ways to contribute. However, a good bug report has some very specific qualities, so please read over our short document on [reporting bugs](https://github.com/coreos/etcd/blob/master/Documentation/reporting_bugs.md) before submitting a bug report. This document might contain links to known issues, another good reason to take a look there before reporting a bug.
Reporting bugs is one of the best ways to contribute. However, a good bug report has some very specific qualities, so please read over our short document on [reporting bugs](https://etcd.io/docs/latest/reporting_bugs) before submitting a bug report. This document might contain links to known issues, another good reason to take a look there before reporting a bug.
## Contribution flow
This is a rough outline of what a contributor's workflow looks like:
- Create a topic branch from where to base the contribution. This is usually master.
- Create a topic branch from where to base the contribution. This is usually main.
- Make commits of logical units.
- Make sure commit messages are in the proper format (see below).
- Push changes in a topic branch to a personal fork of the repository.
- Submit a pull request to coreos/etcd.
- Submit a pull request to etcd-io/etcd.
- The PR must receive a LGTM from two maintainers found in the MAINTAINERS file.
Thanks for contributing!
@ -42,9 +43,13 @@ questions: what changed and why. The subject line should feature the what and
the body of the commit should describe the why.
```
scripts: add the test-cluster command
etcdserver: add grpc interceptor to log info on incoming requests
this uses tmux to setup a test cluster that can easily be killed and started for debugging.
To improve debuggability of etcd v3. Added a grpc interceptor to log
info on incoming requests to etcd server. The log output includes
remote client info, request content (with value field redacted), request
handling latency, response size, etc. Uses zap logger if available,
otherwise uses capnslog.
Fixes #38
```
@ -52,11 +57,38 @@ Fixes #38
The format can be described more formally as follows:
```
<subsystem>: <what changed>
<package>: <what changed>
<BLANK LINE>
<why this change was made>
<BLANK LINE>
<footer>
```
The first line is the subject and should be no longer than 70 characters, the second line is always blank, and other lines should be wrapped at 80 characters. This allows the message to be easier to read on GitHub as well as in various git tools.
The first line is the subject and should be no longer than 70 characters, the second
line is always blank, and other lines should be wrapped at 80 characters. This allows
the message to be easier to read on GitHub as well as in various git tools.
### Pull request across multiple files and packages
If multiple files in a package are changed in a pull request for example:
```
etcdserver/config.go
etcdserver/corrupt.go
```
At the end of the review process if multiple commits exist for a single package they
should be squashed/rebased into a single commit before being merged.
```
etcdserver: <what changed>
[..]
```
If a pull request spans many packages these commits should be squashed/rebased into a single
commit using message with a more generic `*:` prefix.
etcd is a distributed key-value store designed to reliably and quickly preserve and provide access to critical data. It enables reliable distributed coordination through distributed locking, leader elections, and write barriers. An etcd cluster is intended for high availability and permanent data storage and retrieval.
These documents have moved to the [etcd-io/website repo](https://github.com/etcd-io/website/), and can be viewed live at [https://etcd.io/docs/latest/](https://etcd.io/docs/latest/).
- 1x dedicated local SSD mounted under /var/lib/etcd
- 1x dedicated slow disk for the OS
- 1.8 GB memory
- 2x CPUs
- etcd version 2.1.0 alpha
## etcd Cluster
3 etcd members, each runs on a single machine
## Testing
Bootstrap another machine and use the [hey HTTP benchmark tool][hey] to send requests to each etcd member. Check the [benchmark hacking guide][hack-benchmark] for detailed instructions.
## Performance
### reading one single key
| key size in bytes | number of clients | target etcd server | read QPS | 90th Percentile Latency (ms) |
- 1x dedicated local SSD mounted as etcd data directory
- 1x dedicated slow disk for the OS
- 1.8 GB memory
- 2x CPUs
## etcd Cluster
3 etcd 2.2.0 members, each runs on a single machine.
Detailed versions:
```
etcd Version: 2.2.0
Git SHA: e4561dd
Go Version: go1.5
Go OS/Arch: linux/amd64
```
## Testing
Bootstrap another machine, outside of the etcd cluster, and run the [`hey` HTTP benchmark tool](https://github.com/rakyll/hey) with a connection reuse patch to send requests to each etcd cluster member. See the [benchmark instructions](../../hack/benchmark/) for the patch and the steps to reproduce our procedures.
The performance is calulated through results of 100 benchmark rounds.
## Performance
### Single Key Read Performance
| key size in bytes | number of clients | target etcd server | average read QPS | read QPS stddev | average 90th Percentile Latency (ms) | latency stddev |
- Because etcd now records metrics for each API call, read QPS performance seems to see a minor decrease in most scenarios. This minimal performance impact was judged a reasonable investment for the breadth of monitoring and debugging information returned.
- Write QPS to cluster leaders seems to be increased by a small margin. This is because the main loop and entry apply loops were decoupled in the etcd raft logic, eliminating several blocks between them.
- Write QPS to all members seems to be increased by a significant margin, because followers now receive the latest commit index sooner, and commit proposals more quickly.
- 1x dedicated local SSD mounted under /var/lib/etcd
- 1x dedicated slow disk for the OS
- 1.8 GB memory
- 2x CPUs
## etcd Cluster
3 etcd 2.2.0-rc members, each runs on a single machine.
Detailed versions:
```
etcd Version: 2.2.0-alpha.1+git
Git SHA: 59a5a7e
Go Version: go1.4.2
Go OS/Arch: linux/amd64
```
Also, we use 3 etcd 2.1.0 alpha-stage members to form cluster to get base performance. etcd's commit head is at [c7146bd5][c7146bd5], which is the same as the one that we use in [etcd 2.1 benchmark][etcd-2.1-benchmark].
## Testing
Bootstrap another machine and use the [hey HTTP benchmark tool][hey] to send requests to each etcd member. Check the [benchmark hacking guide][hack-benchmark] for detailed instructions.
## Performance
### reading one single key
| key size in bytes | number of clients | target etcd server | read QPS | 90th Percentile Latency (ms) |
- read QPS in most scenarios is decreased by 5~8%. The reason is that etcd records store metrics for each store operation. The metrics is important for monitoring and debugging, so this is acceptable.
- write QPS to leader is increased by 20~30%. This is because we decouple raft main loop and entry apply loop, which avoids them blocking each other.
- write QPS to all servers is increased by 30~80% because follower could receive latest commit index earlier and commit proposals faster.
- When etcd reaches data size threshold, it may trigger leader election easily and drop part of proposals.
- For most cases, the etcd cluster should work smoothly if it doesn't hit the threshold. If it doesn't work well due to insufficient resources, decrease its data size.
| value bytes | key number limitation | suggested data size threshold(MB) | consumed RSS(MB) |
*NOTE*: The watch features are under active development, and their memory usage may change as that development progresses. We do not expect it to significantly increase beyond the figures stated below.
A primary goal of etcd is supporting a very large number of watchers doing a massively large amount of watching. etcd aims to support O(10k) clients, O(100K) watch streams (O(10) streams per client) and O(10M) total watchings (O(100) watching per stream). The memory consumed by each individual watching accounts for the largest portion of etcd's overall usage, and is therefore the focus of current and future optimizations.
Three related components of etcd watch consume physical memory: each `grpc.Conn`, each watch stream, and each instance of the watching activity. `grpc.Conn` maintains the actual TCP connection and other gRPC connection state. Each `grpc.Conn` consumes O(10kb) of memory, and might have multiple watch streams attached.
Each watch stream is an independent HTTP2 connection which consumes another O(10kb) of memory.
Multiple watchings might share one watch stream.
Watching is the actual struct that tracks the changes on the key-value store. Each watching should only consume <O(1kb).
Two components of etcd storage consume physical memory. The etcd process allocates an *in-memory index* to speed key lookup. The process's *page cache*, managed by the operating system, stores recently-accessed data from disk for quick re-use.
The in-memory index holds all the keys in a [B-tree][btree] data structure, along with pointers to the on-disk data (the values). Each key in the B-tree may contain multiple pointers, pointing to different versions of its values. The theoretical memory consumption of the in-memory index can hence be approximated with the formula:
where `c1` is the key metadata overhead and `c2` is the version metadata overhead.
The graph shows the detailed structure of the in-memory index B-tree.
```
In mem index
+------------+
| key || ... |
+--------------+ | || |
| | +------------+
| | | v1 || ... |
| disk <----------------| || | Tree Node
| | +------------+
| | | v2 || ... |
| <----------------+ || |
| | +------------+
+--------------+ +-----+ | | |
| | | | |
| +------------+
|
|
^
------+
| ... |
| |
+-----+
| ... | Tree Node
| |
+-----+
| ... |
| |
------+
```
[Page cache memory][pagecache] is managed by the operating system and is not covered in detail in this document.
## Testing Environment
etcd version
- git head https://github.com/coreos/etcd/commit/776e9fb7be7eee5e6b58ab977c8887b4fe4d48db
GCE n1-standard-2 machine type
- 7.5 GB memory
- 2x CPUs
## In-memory index memory usage
In this test, we only benchmark the memory usage of the in-memory index. The goal is to find `c1` and `c2` mentioned above and to understand the hard limit of memory consumption of the storage.
We calculate the memory usage consumption via the Go runtime.ReadMemStats. We calculate the total allocated bytes difference before creating the index and after creating the index. It cannot perfectly reflect the memory usage of the in-memory index itself but can show the rough consumption pattern.
| N | versions | key size | memory usage |
|------|----------|----------|--------------|
| 100K | 1 | 64bytes | 22MB |
| 100K | 5 | 64bytes | 39MB |
| 1M | 1 | 64bytes | 218MB |
| 1M | 5 | 64bytes | 432MB |
| 100K | 1 | 256bytes | 41MB |
| 100K | 5 | 256bytes | 65MB |
| 1M | 1 | 256bytes | 409MB |
| 1M | 5 | 256bytes | 506MB |
Based on the result, we can calculate `c1=120bytes`, `c2=30bytes`. We only need two sets of data to calculate `c1` and `c2`, since they are the only unknown variable in the formula. The `c1=120bytes` and `c2=30bytes` are the average value of the 4 sets of `c1` and `c2` we calculated. The key metadata overhead is still relatively nontrivial (50%) for small key-value pairs. However, this is a significant improvement over the old store, which had at least 1000% overhead.
## Overall memory usage
The overall memory usage captures how much RSS etcd consumes with the storage. The value size should have very little impact on the overall memory usage of etcd, since we keep values on disk and only retain hot values in memory, managed by the OS page cache.
| N | versions | key size | value size | memory usage |
Based on the result, we know the value size does not significantly impact the memory consumption. There is some minor increase due to more data held in the OS page cache.
* New development occurs on the [master branch][master].
* Master branch should always have a green build!
* Backwards-compatible bug fixes should target the master branch and subsequently be ported to stable branches.
* Once the master branch is ready for release, it will be tagged and become the new stable branch.
The etcd team has adopted a *rolling release model* and supports two stable versions of etcd.
### Master branch
The `master` branch is our development branch. All new features land here first.
To try new and experimental features, pull `master` and play with it. Note that `master` may not be stable because new features may introduce bugs.
Before the release of the next stable version, feature PRs will be frozen. We will focus on the testing, bug-fix and documentation for one to two weeks.
### Stable branches
All branches with prefix `release-` are considered _stable_ branches.
After every minor release (http://semver.org/), we will have a new stable branch for that release. We will keep fixing the backwards-compatible bugs for the latest two stable releases. A _patch_ release to each supported release branch, incorporating any bug fixes, will be once every two weeks, given any patches.
| Lock | LockRequest | LockResponse | Lock acquires a distributed shared lock on a given named lock. On success, it will return a unique key that exists so long as the lock is held by the caller. This key can be used in conjunction with transactions to safely ensure updates to etcd only occur while holding lock ownership. The lock is held until Unlock is called on the key or the lease associate with the owner expires. |
| Unlock | UnlockRequest | UnlockResponse | Unlock takes a key returned by Lock and releases the hold on lock. The next Lock caller waiting for the lock will then be woken up and given ownership of the lock. |
| name | name is the identifier for the distributed shared lock to be acquired. | bytes |
| lease | lease is the ID of the lease that will be attached to ownership of the lock. If the lease expires or is revoked and currently holds the lock, the lock is automatically released. Calls to Lock with the same lease will be treated as a single acquistion; locking twice with the same lease is a no-op. | int64 |
| key | key is a key that will exist on etcd for the duration that the Lock caller owns the lock. Users should not modify this key or the lock may exhibit undefined behavior. | bytes |
| Campaign | CampaignRequest | CampaignResponse | Campaign waits to acquire leadership in an election, returning a LeaderKey representing the leadership if successful. The LeaderKey can then be used to issue new values on the election, transactionally guard API requests on leadership still being held, and resign from the election. |
| Proclaim | ProclaimRequest | ProclaimResponse | Proclaim updates the leader's posted value with a new value. |
| Leader | LeaderRequest | LeaderResponse | Leader returns the current election proclamation, if any. |
| Observe | LeaderRequest | LeaderResponse | Observe streams election proclamations in-order as made by the election's elected leaders. |
| Resign | ResignRequest | ResignResponse | Resign releases election leadership so other campaigners may acquire leadership on the election. |
| name | name is the election's identifier for the campaign. | bytes |
| lease | lease is the ID of the lease attached to leadership of the election. If the lease expires or is revoked before resigning leadership, then the leadership is transferred to the next campaigner, if any. | int64 |
| value | value is the initial proclaimed value set when the campaigner wins the election. | bytes |
| name | name is the election identifier that correponds to the leadership key. | bytes |
| key | key is an opaque key representing the ownership of the election. If the key is deleted, then leadership is lost. | bytes |
| rev | rev is the creation revision of the key. It can be used to test for ownership of an election during transactions by testing the key's creation revision matches rev. | int64 |
| lease | lease is the lease ID of the election leader. | int64 |
| type | type is the kind of event. If type is a PUT, it indicates new data has been stored to the key. If type is a DELETE, it indicates the key was deleted. | EventType |
| kv | kv holds the KeyValue for the event. A PUT event contains current kv pair. A PUT event with kv.Version=1 indicates the creation of a key. A DELETE/EXPIRE event contains the deleted key with its modification revision set to the revision of deletion. | KeyValue |
| prev_kv | prev_kv holds the key-value pair before the event happens. | KeyValue |
##### message `KeyValue` (mvcc/mvccpb/kv.proto)
| Field | Description | Type |
| ----- | ----------- | ---- |
| key | key is the key in bytes. An empty key is not allowed. | bytes |
| create_revision | create_revision is the revision of last creation on this key. | int64 |
| mod_revision | mod_revision is the revision of last modification on this key. | int64 |
| version | version is the version of the key. A deletion resets the version to zero and any modification of the key increases its version. | int64 |
| value | value is the value held by the key, in bytes. | bytes |
| lease | lease is the ID of the lease that attached to key. When the attached lease expires, the key will be deleted. If lease is 0, then no lease is attached to the key. | int64 |
etcd v3 uses [gRPC][grpc] for its messaging protocol. The etcd project includes a gRPC-based [Go client][go-client] and a command line utility, [etcdctl][etcdctl], for communicating with an etcd cluster through gRPC. For languages with no gRPC support, etcd provides a JSON [grpc-gateway][grpc-gateway]. This gateway serves a RESTful proxy that translates HTTP/JSON requests into gRPC messages.
## Using grpc-gateway
The gateway accepts a [JSON mapping][json-mapping] for etcd's [protocol buffer][api-ref] message definitions. Note that `key` and `value` fields are defined as byte arrays and therefore must be base64 encoded in JSON. The following examples use `curl`, but any HTTP/JSON client should work all the same.
### Put and get keys
Use the `/v3beta/kv/range` and `/v3beta/kv/put` services to read and write keys:
| RoleGrantPermission | AuthRoleGrantPermissionRequest | AuthRoleGrantPermissionResponse | RoleGrantPermission grants a permission of a specified key or range to a specified role. |
| RoleRevokePermission | AuthRoleRevokePermissionRequest | AuthRoleRevokePermissionResponse | RoleRevokePermission revokes a key or range permission of a specified role. |
##### service `Cluster` (etcdserver/etcdserverpb/rpc.proto)
| Method | Request Type | Response Type | Description |
| Range | RangeRequest | RangeResponse | Range gets the keys in the range from the key-value store. |
| Put | PutRequest | PutResponse | Put puts the given key into the key-value store. A put request increments the revision of the key-value store and generates one event in the event history. |
| DeleteRange | DeleteRangeRequest | DeleteRangeResponse | DeleteRange deletes the given range from the key-value store. A delete request increments the revision of the key-value store and generates a delete event in the event history for every deleted key. |
| Txn | TxnRequest | TxnResponse | Txn processes multiple requests in a single transaction. A txn request increments the revision of the key-value store and generates events with the same revision for every completed request. It is not allowed to modify the same key several times within one txn. |
| Compact | CompactionRequest | CompactionResponse | Compact compacts the event history in the etcd key-value store. The key-value store should be periodically compacted or the event history will continue to grow indefinitely. |
##### service `Lease` (etcdserver/etcdserverpb/rpc.proto)
| Method | Request Type | Response Type | Description |
| LeaseGrant | LeaseGrantRequest | LeaseGrantResponse | LeaseGrant creates a lease which expires if the server does not receive a keepAlive within a given time to live period. All keys attached to the lease will be expired and deleted if the lease expires. Each expired key generates a delete event in the event history. |
| LeaseRevoke | LeaseRevokeRequest | LeaseRevokeResponse | LeaseRevoke revokes a lease. All keys attached to the lease will expire and be deleted. |
| LeaseKeepAlive | LeaseKeepAliveRequest | LeaseKeepAliveResponse | LeaseKeepAlive keeps the lease alive by streaming keep alive requests from the client to the server and streaming keep alive responses from the server to the client. |
| Status | StatusRequest | StatusResponse | Status gets the status of the member. |
| Defragment | DefragmentRequest | DefragmentResponse | Defragment defragments a member's backend database to recover storage space. |
| Hash | HashRequest | HashResponse | Hash computes the hash of the KV's backend. This is designed for testing; do not use this in production when there are ongoing transactions. |
| HashKV | HashKVRequest | HashKVResponse | HashKV computes the hash of all MVCC keys up to a given revision. |
| Snapshot | SnapshotRequest | SnapshotResponse | Snapshot sends a snapshot of the entire backend from a member over a stream to a client. |
| MoveLeader | MoveLeaderRequest | MoveLeaderResponse | MoveLeader requests current leader node to transfer its leadership to transferee. |
##### service `Watch` (etcdserver/etcdserverpb/rpc.proto)
| Method | Request Type | Response Type | Description |
| Watch | WatchRequest | WatchResponse | Watch watches for events happening or that have happened. Both input and output are streams; the input stream is for creating and canceling watchers and the output stream sends events. One watch RPC can watch on multiple key ranges, streaming events for several watches at once. The entire event history can be watched starting from the last compaction revision. |
| action | action is the kind of alarm request to issue. The action may GET alarm statuses, ACTIVATE an alarm, or DEACTIVATE a raised alarm. | AlarmAction |
| memberID | memberID is the ID of the member associated with the alarm. If memberID is 0, the alarm request covers all members. | uint64 |
| alarm | alarm is the type of alarm to consider for this request. | AlarmType |
CompactionRequest compacts the key-value store up to a given revision. All superseded keys with a revision less than the compaction revision will be removed.
| Field | Description | Type |
| ----- | ----------- | ---- |
| revision | revision is the key-value store revision for the compaction operation. | int64 |
| physical | physical is set so the RPC will wait until the compaction is physically applied to the local database such that compacted entries are totally removed from the backend database. | bool |
| result | result is logical comparison operation for this comparison. | CompareResult |
| target | target is the key-value field to inspect for the comparison. | CompareTarget |
| key | key is the subject key for the comparison operation. | bytes |
| target_union | | oneof |
| version | version is the version of the given key | int64 |
| create_revision | create_revision is the creation revision of the given key | int64 |
| mod_revision | mod_revision is the last modified revision of the given key. | int64 |
| value | value is the value of the given key, in bytes. | bytes |
| lease | lease is the lease id of the given key. | int64 |
| range_end | range_end compares the given target to all keys in the range [key, range_end). See RangeRequest for more details on key ranges. | bytes |
| key | key is the first key to delete in the range. | bytes |
| range_end | range_end is the key following the last key to delete for the range [key, range_end). If range_end is not given, the range is defined to contain only the key argument. If range_end is one bit larger than the given key, then the range is all the keys with the prefix (the given key). If range_end is '\0', the range is all keys greater than or equal to the key argument. | bytes |
| prev_kv | If prev_kv is set, etcd gets the previous key-value pairs before deleting it. The previous key-value pairs will be returned in the delete response. | bool |
| ID | ID is the member ID for this member. | uint64 |
| name | name is the human-readable name of the member. If the member is not started, the name will be an empty string. | string |
| peerURLs | peerURLs is the list of URLs the member exposes to the cluster for communication. | (slice of) string |
| clientURLs | clientURLs is the list of URLs the member exposes to clients for communication. If the member is not started, clientURLs will be empty. | (slice of) string |
| key | key is the key, in bytes, to put into the key-value store. | bytes |
| value | value is the value, in bytes, to associate with the key in the key-value store. | bytes |
| lease | lease is the lease ID to associate with the key in the key-value store. A lease value of 0 indicates no lease. | int64 |
| prev_kv | If prev_kv is set, etcd gets the previous key-value pair before changing it. The previous key-value pair will be returned in the put response. | bool |
| ignore_value | If ignore_value is set, etcd updates the key using its current value. Returns an error if the key does not exist. | bool |
| ignore_lease | If ignore_lease is set, etcd updates the key using its current lease. Returns an error if the key does not exist. | bool |
| key | key is the first key for the range. If range_end is not given, the request only looks up key. | bytes |
| range_end | range_end is the upper bound on the requested range [key, range_end). If range_end is '\0', the range is all keys >= key. If range_end is key plus one (e.g., "aa"+1 == "ab", "a\xff"+1 == "b"), then the range request gets all keys prefixed with key. If both key and range_end are '\0', then the range request returns all keys. | bytes |
| limit | limit is a limit on the number of keys returned for the request. When limit is set to 0, it is treated as no limit. | int64 |
| revision | revision is the point-in-time of the key-value store to use for the range. If revision is less or equal to zero, the range is over the newest key-value store. If the revision has been compacted, ErrCompacted is returned as a response. | int64 |
| sort_order | sort_order is the order for returned sorted results. | SortOrder |
| sort_target | sort_target is the key-value field to use for sorting. | SortTarget |
| serializable | serializable sets the range request to use serializable member-local reads. Range requests are linearizable by default; linearizable requests have higher latency and lower throughput than serializable requests but reflect the current consensus of the cluster. For better performance, in exchange for possible stale reads, a serializable range request is served locally without needing to reach consensus with other nodes in the cluster. | bool |
| keys_only | keys_only when set returns only the keys and not the values. | bool |
| count_only | count_only when set returns only the count of the keys in the range. | bool |
| min_mod_revision | min_mod_revision is the lower bound for returned key mod revisions; all keys with lesser mod revisions will be filtered away. | int64 |
| max_mod_revision | max_mod_revision is the upper bound for returned key mod revisions; all keys with greater mod revisions will be filtered away. | int64 |
| min_create_revision | min_create_revision is the lower bound for returned key create revisions; all keys with lesser create trevisions will be filtered away. | int64 |
| max_create_revision | max_create_revision is the upper bound for returned key create revisions; all keys with greater create revisions will be filtered away. | int64 |
| header | header has the current key-value store information. The first header in the snapshot stream indicates the point in time of the snapshot. | ResponseHeader |
| remaining_bytes | remaining_bytes is the number of blob bytes to be sent after this message | uint64 |
| blob | blob contains the next chunk of the snapshot in the snapshot stream. | bytes |
From google paxosdb paper: Our implementation hinges around a powerful primitive which we call MultiOp. All other database operations except for iteration are implemented as a single call to MultiOp. A MultiOp is applied atomically and consists of three components: 1. A list of tests called guard. Each test in guard checks a single entry in the database. It may check for the absence or presence of a value, or compare with a given value. Two different tests in the guard may apply to the same or different entries in the database. All tests in the guard are applied and MultiOp returns the results. If all tests are true, MultiOp executes t op (see item 2 below), otherwise it executes f op (see item 3 below). 2. A list of database operations called t op. Each operation in the list is either an insert, delete, or lookup operation, and applies to a single database entry. Two different operations in the list may apply to the same or different entries in the database. These operations are executed if guard evaluates to true. 3. A list of database operations called f op. Like t op, but executed if guard evaluates to false.
| Field | Description | Type |
| ----- | ----------- | ---- |
| compare | compare is a list of predicates representing a conjunction of terms. If the comparisons succeed, then the success requests will be processed in order, and the response will contain their respective responses in order. If the comparisons fail, then the failure requests will be processed in order, and the response will contain their respective responses in order. | (slice of) Compare |
| success | success is a list of requests which will be applied when compare evaluates to true. | (slice of) RequestOp |
| failure | failure is a list of requests which will be applied when compare evaluates to false. | (slice of) RequestOp |
| succeeded | succeeded is set to true if the compare evaluated to true or false otherwise. | bool |
| responses | responses is a list of responses corresponding to the results from applying success if succeeded is true or failure if succeeded is false. | (slice of) ResponseOp |
| key | key is the key to register for watching. | bytes |
| range_end | range_end is the end of the range [key, range_end) to watch. If range_end is not given, only the key argument is watched. If range_end is equal to '\0', all keys greater than or equal to the key argument are watched. If the range_end is one bit larger than the given key, then all keys with the prefix (the given key) will be watched. | bytes |
| start_revision | start_revision is an optional revision to watch from (inclusive). No start_revision is "now". | int64 |
| progress_notify | progress_notify is set so that the etcd server will periodically send a WatchResponse with no events to the new watcher if there are no recent events. It is useful when clients wish to recover a disconnected watcher starting from a recent known revision. The etcd server may decide how often it will send notifications based on current load. | bool |
| filters | filters filter the events at server side before it sends back to the watcher. | (slice of) FilterType |
| prev_kv | If prev_kv is set, created watcher gets the previous KV before the event happens. If the previous KV is already compacted, nothing will be returned. | bool |
| watch_id | watch_id is the ID of the watcher that corresponds to the response. | int64 |
| created | created is set to true if the response is for a create watch request. The client should record the watch_id and expect to receive events for the created watcher from the same stream. All events sent to the created watcher will attach with the same watch_id. | bool |
| canceled | canceled is set to true if the response is for a cancel watch request. No further events will be sent to the canceled watcher. | bool |
| compact_revision | compact_revision is set to the minimum index if a watcher tries to watch at a compacted index. This happens when creating a watcher at a compacted revision or the watcher cannot catch up with the progress of the key-value store. The client should treat the watcher as canceled and should not try to create any watcher with the same start_revision again. | int64 |
| cancel_reason | cancel_reason indicates the reason for canceling the watcher. | string |
| events | | (slice of) mvccpb.Event |
##### message `Event` (mvcc/mvccpb/kv.proto)
| Field | Description | Type |
| ----- | ----------- | ---- |
| type | type is the kind of event. If type is a PUT, it indicates new data has been stored to the key. If type is a DELETE, it indicates the key was deleted. | EventType |
| kv | kv holds the KeyValue for the event. A PUT event contains current kv pair. A PUT event with kv.Version=1 indicates the creation of a key. A DELETE/EXPIRE event contains the deleted key with its modification revision set to the revision of deletion. | KeyValue |
| prev_kv | prev_kv holds the key-value pair before the event happens. | KeyValue |
##### message `KeyValue` (mvcc/mvccpb/kv.proto)
| Field | Description | Type |
| ----- | ----------- | ---- |
| key | key is the key in bytes. An empty key is not allowed. | bytes |
| create_revision | create_revision is the revision of last creation on this key. | int64 |
| mod_revision | mod_revision is the revision of last modification on this key. | int64 |
| version | version is the version of the key. A deletion resets the version to zero and any modification of the key increases its version. | int64 |
| value | value is the value held by the key, in bytes. | bytes |
| lease | lease is the ID of the lease that attached to key. When the attached lease expires, the key will be deleted. If lease is 0, then no lease is attached to the key. | int64 |
"summary":"Campaign waits to acquire leadership in an election, returning a LeaderKey\nrepresenting the leadership if successful. The LeaderKey can then be used\nto issue new values on the election, transactionally guard API requests on\nleadership still being held, and resign from the election.",
"summary":"Resign releases election leadership so other campaigners may acquire\nleadership on the election.",
"operationId":"Resign",
"operationId":"Election_Resign",
"responses":{
"200":{
"description":"",
"description":"A successful response.",
"schema":{
"$ref":"#/definitions/v3electionpbResignResponse"
}
},
"default":{
"description":"An unexpected error response",
"schema":{
"$ref":"#/definitions/runtimeError"
}
}
},
"parameters":[
@ -168,7 +203,7 @@
"revision":{
"type":"string",
"format":"int64",
"description":"revision is the key-value store revision when the request was applied."
"description":"revision is the key-value store revision when the request was applied.\nFor watch progress responses, the header.revision indicates progress. All future events\nrecieved in this stream are guaranteed to have a higher revision number than the\nheader.revision number."
"summary":"Lock acquires a distributed shared lock on a given named lock.\nOn success, it will return a unique key that exists so long as the\nlock is held by the caller. This key can be used in conjunction with\ntransactions to safely ensure updates to etcd only occur while holding\nlock ownership. The lock is held until Unlock is called on the key or the\nlease associate with the owner expires.",
"operationId":"Lock",
"operationId":"Lock_Lock",
"responses":{
"200":{
"description":"",
"description":"A successful response.",
"schema":{
"$ref":"#/definitions/v3lockpbLockResponse"
}
},
"default":{
"description":"An unexpected error response",
"schema":{
"$ref":"#/definitions/runtimeError"
}
}
},
"parameters":[
@ -42,16 +44,22 @@
]
}
},
"/v3beta/lock/unlock":{
"/v3/lock/unlock":{
"post":{
"summary":"Unlock takes a key returned by Lock and releases the hold on lock. The\nnext Lock caller waiting for the lock will then be woken up and given\nownership of the lock.",
"operationId":"Unlock",
"operationId":"Lock_Unlock",
"responses":{
"200":{
"description":"",
"description":"A successful response.",
"schema":{
"$ref":"#/definitions/v3lockpbUnlockResponse"
}
},
"default":{
"description":"An unexpected error response",
"schema":{
"$ref":"#/definitions/runtimeError"
}
}
},
"parameters":[
@ -87,7 +95,7 @@
"revision":{
"type":"string",
"format":"int64",
"description":"revision is the key-value store revision when the request was applied."
"description":"revision is the key-value store revision when the request was applied.\nFor watch progress responses, the header.revision indicates progress. All future events\nrecieved in this stream are guaranteed to have a higher revision number than the\nheader.revision number."
},
"raft_term":{
"type":"string",
@ -96,6 +104,39 @@
}
}
},
"protobufAny":{
"type":"object",
"properties":{
"type_url":{
"type":"string"
},
"value":{
"type":"string",
"format":"byte"
}
}
},
"runtimeError":{
"type":"object",
"properties":{
"error":{
"type":"string"
},
"code":{
"type":"integer",
"format":"int32"
},
"message":{
"type":"string"
},
"details":{
"type":"array",
"items":{
"$ref":"#/definitions/protobufAny"
}
}
}
},
"v3lockpbLockRequest":{
"type":"object",
"properties":{
@ -107,7 +148,7 @@
"lease":{
"type":"string",
"format":"int64",
"description":"lease is the ID of the lease that will be attached to ownership of the\nlock. If the lease expires or is revoked and currently holds the lock,\nthe lock is automatically released. Calls to Lock with the same lease will\nbe treated as a single acquistion; locking twice with the same lease is a\nno-op."
"description":"lease is the ID of the lease that will be attached to ownership of the\nlock. If the lease expires or is revoked and currently holds the lock,\nthe lock is automatically released. Calls to Lock with the same lease will\nbe treated as a single acquisition; locking twice with the same lease is a\nno-op."
For the most part, the etcd project is stable, but we are still moving fast! We believe in the release fast philosophy. We want to get early feedback on features still in development and stabilizing. Thus, there are, and will be more, experimental features and APIs. We plan to improve these features based on the early feedback from the community, or abandon them if there is little interest, in the next few releases. Please do not rely on any experimental features or APIs in production environment.
## The current experimental API/features are:
- [KV ordering](https://godoc.org/github.com/coreos/etcd/clientv3/ordering) wrapper. When an etcd client switches endpoints, responses to serializable reads may go backward in time if the new endpoint is lagging behind the rest of the cluster. The ordering wrapper caches the current cluster revision from response headers. If a response revision is less than the cached revision, the client selects another endpoint and reissues the read. Enable in grpcproxy with `--experimental-serializable-ordering`.
etcd provides a gRPC resolver to support an alternative name system that fetches endpoints from etcd for discovering gRPC services. The underlying mechanism is based on watching updates to keys prefixed with the service name.
## Using etcd discovery with go-grpc
The etcd client provides a gRPC resolver for resolving gRPC endpoints with an etcd backend. The resolver is initialized with an etcd client and given a target for resolution:
The etcd resolver treats all keys under the prefix of the resolution target following a "/" (e.g., "my-service/") with JSON-encoded go-grpc `naming.Update` values as potential service endpoints. Endpoints are added to the service by creating new keys and removed from the service by deleting keys.
### Adding an endpoint
New endpoints can be added to the service through `etcdctl`:
```sh
ETCDCTL_API=3 etcdctl put my-service/1.2.3.4 '{"Addr":"1.2.3.4","Metadata":"..."}'
```
The etcd client's `GRPCResolver.Update` method can also register new endpoints with a key matching the `Addr`:
Registering an endpoint with a lease ensures that if the host can't maintain a keepalive heartbeat (e.g., its machine fails), it will be removed from the service:
```sh
lease=`ETCDCTL_API=3 etcdctl lease grant 5| cut -f2 -d' '`
ETCDCTL_API=3 etcdctl put --lease=$lease my-service/1.2.3.4 '{"Addr":"1.2.3.4","Metadata":"..."}'
Users mostly interact with etcd by putting or getting the value of a key. This section describes how to do that by using etcdctl, a command line tool for interacting with etcd server. The concepts described here should apply to the gRPC APIs or client library APIs.
By default, etcdctl talks to the etcd server with the v2 API for backward compatibility. For etcdctl to speak to etcd using the v3 API, the API version must be set to version 3 via the `ETCDCTL_API` environment variable. However note that any key that was created using the v2 API will not be able to be queried via the v3 API. A v3 API ```etcdctl get``` of a v2 key will exit with 0 and no key data, this is the expected behaviour.
```bash
export ETCDCTL_API=3
```
## Find versions
etcdctl version and Server API version can be useful in finding the appropriate commands to be used for performing various operations on etcd.
Here is the command to find the versions:
```bash
$ etcdctl version
etcdctl version: 3.1.0-alpha.0+git
API version: 3.1
```
## Write a key
Applications store keys into the etcd cluster by writing to keys. Every stored key is replicated to all etcd cluster members through the Raft protocol to achieve consistency and reliability.
Here is the command to set the value of key `foo` to `bar`:
```bash
$ etcdctl put foo bar
OK
```
Also a key can be set for a specified interval of time by attaching lease to it.
Here is the command to set the value of key `foo1` to `bar1` for 10s.
```bash
$ etcdctl put foo1 bar1 --lease=1234abcd
OK
```
Note: The lease id `1234abcd` in the above command refers to id returned on creating the lease of 10s. This id can then be attached to the key.
## Read keys
Applications can read values of keys from an etcd cluster. Queries may read a single key, or a range of keys.
Suppose the etcd cluster has stored the following keys:
```bash
foo = bar
foo1 = bar1
foo2 = bar2
foo3 = bar3
```
Here is the command to read the value of key `foo`:
```bash
$ etcdctl get foo
foo
bar
```
Here is the command to read the value of key `foo` in hex format:
```bash
$ etcdctl get foo --hex
\x66\x6f\x6f # Key
\x62\x61\x72 # Value
```
Here is the command to read only the value of key `foo`:
```bash
$ etcdctl get foo --print-value-only
bar
```
Here is the command to range over the keys from `foo` to `foo3`:
```bash
$ etcdctl get foo foo3
foo
bar
foo1
bar1
foo2
bar2
```
Note that `foo3` is excluded since the range is over the half-open interval `[foo, foo3)`, excluding `foo3`.
Here is the command to range over all keys prefixed with `foo`:
```bash
$ etcdctl get --prefix foo
foo
bar
foo1
bar1
foo2
bar2
foo3
bar3
```
Here is the command to range over all keys prefixed with `foo`, limiting the number of results to 2:
```bash
$ etcdctl get --prefix --limit=2 foo
foo
bar
foo1
bar1
```
## Read past version of keys
Applications may want to read superseded versions of a key. For example, an application may wish to roll back to an old configuration by accessing an earlier version of a key. Alternatively, an application may want a consistent view over multiple keys through multiple requests by accessing key history.
Since every modification to the etcd cluster key-value store increments the global revision of an etcd cluster, an application can read superseded keys by providing an older etcd revision.
Suppose an etcd cluster already has the following keys:
```bash
foo = bar # revision = 2
foo1 = bar1 # revision = 3
foo = bar_new # revision = 4
foo1 = bar1_new # revision = 5
```
Here are an example to access the past versions of keys:
```bash
$ etcdctl get --prefix foo # access the most recent versions of keys
foo
bar_new
foo1
bar1_new
$ etcdctl get --prefix --rev=4 foo # access the versions of keys at revision 4
foo
bar_new
foo1
bar1
$ etcdctl get --prefix --rev=3 foo # access the versions of keys at revision 3
foo
bar
foo1
bar1
$ etcdctl get --prefix --rev=2 foo # access the versions of keys at revision 2
foo
bar
$ etcdctl get --prefix --rev=1 foo # access the versions of keys at revision 1
```
## Read keys which are greater than or equal to the byte value of the specified key
Applications may want to read keys which are greater than or equal to the byte value of the specified key.
Suppose an etcd cluster already has the following keys:
```bash
a = 123
b = 456
z = 789
```
Here is the command to read keys which are greater than or equal to the byte value of key `b` :
```bash
$ etcdctl get --from-key b
b
456
z
789
```
## Delete keys
Applications can delete a key or a range of keys from an etcd cluster.
Suppose an etcd cluster already has the following keys:
```bash
foo = bar
foo1 = bar1
foo3 = bar3
zoo = val
zoo1 = val1
zoo2 = val2
a = 123
b = 456
z = 789
```
Here is the command to delete key `foo`:
```bash
$ etcdctl del foo
1 # one key is deleted
```
Here is the command to delete keys ranging from `foo` to `foo9`:
```bash
$ etcdctl del foo foo9
2 # two keys are deleted
```
Here is the command to delete key `zoo` with the deleted key value pair returned:
```bash
$ etcdctl del --prev-kv zoo
1 # one key is deleted
zoo # deleted key
val # the value of the deleted key
```
Here is the command to delete keys having prefix as `zoo`:
```bash
$ etcdctl del --prefix zoo
2 # two keys are deleted
```
Here is the command to delete keys which are greater than or equal to the byte value of key `b` :
```bash
$ etcdctl del --from-key b
2 # two keys are deleted
```
## Watch key changes
Applications can watch on a key or a range of keys to monitor for any updates.
Here is the command to watch on key `foo`:
```bash
$ etcdctl watch foo
# in another terminal: etcdctl put foo bar
PUT
foo
bar
```
Here is the command to watch on key `foo` in hex format:
```bash
$ etcdctl watch foo --hex
# in another terminal: etcdctl put foo bar
PUT
\x66\x6f\x6f # Key
\x62\x61\x72 # Value
```
Here is the command to watch on a range key from `foo` to `foo9`:
```bash
$ etcdctl watch foo foo9
# in another terminal: etcdctl put foo bar
PUT
foo
bar
# in another terminal: etcdctl put foo1 bar1
PUT
foo1
bar1
```
Here is the command to watch on keys having prefix `foo`:
```bash
$ etcdctl watch --prefix foo
# in another terminal: etcdctl put foo bar
PUT
foo
bar
# in another terminal: etcdctl put fooz1 barz1
PUT
fooz1
barz1
```
Here is the command to watch on multiple keys `foo` and `zoo`:
```bash
$ etcdctl watch -i
$ watch foo
$ watch zoo
# in another terminal: etcdctl put foo bar
PUT
foo
bar
# in another terminal: etcdctl put zoo val
PUT
zoo
val
```
## Watch historical changes of keys
Applications may want to watch for historical changes of keys in etcd. For example, an application may wish to receive all the modifications of a key; if the application stays connected to etcd, then `watch` is good enough. However, if the application or etcd fails, a change may happen during the failure, and the application will not receive the update in real time. To guarantee the update is delivered, the application must be able to watch for historical changes to keys. To do this, an application can specify a historical revision on a watch, just like reading past version of keys.
Suppose we finished the following sequence of operations:
```bash
$ etcdctl put foo bar # revision = 2
OK
$ etcdctl put foo1 bar1 # revision = 3
OK
$ etcdctl put foo bar_new # revision = 4
OK
$ etcdctl put foo1 bar1_new # revision = 5
OK
```
Here is an example to watch the historical changes:
```bash
# watch for changes on key `foo` since revision 2
$ etcdctl watch --rev=2 foo
PUT
foo
bar
PUT
foo
bar_new
```
```bash
# watch for changes on key `foo` since revision 3
$ etcdctl watch --rev=3 foo
PUT
foo
bar_new
```
Here is an example to watch only from the last historical change:
```bash
# watch for changes on key `foo` and return last revision value along with modified value
$ etcdctl watch --prev-kv foo
# in another terminal: etcdctl put foo bar_latest
PUT
foo # key
bar_new # last value of foo key before modification
foo # key
bar_latest # value of foo key after modification
```
## Compacted revisions
As we mentioned, etcd keeps revisions so that applications can read past versions of keys. However, to avoid accumulating an unbounded amount of history, it is important to compact past revisions. After compacting, etcd removes historical revisions, releasing resources for future use. All superseded data with revisions before the compacted revision will be unavailable.
Here is the command to compact the revisions:
```bash
$ etcdctl compact 5
compacted revision 5
# any revisions before the compacted one are not accessible
$ etcdctl get --rev=4 foo
Error: rpc error: code = 11 desc = etcdserver: mvcc: required revision has been compacted
```
Note: The current revision of etcd server can be found using get command on any key (existent or non-existent) in json format. Example is shown below for mykey which does not exist in etcd server:
Applications can grant leases for keys from an etcd cluster. When a key is attached to a lease, its lifetime is bound to the lease's lifetime which in turn is governed by a time-to-live (TTL). Each lease has a minimum time-to-live (TTL) value specified by the application at grant time. The lease's actual TTL value is at least the minimum TTL and is chosen by the etcd cluster. Once a lease's TTL elapses, the lease expires and all attached keys are deleted.
Here is the command to grant a lease:
```bash
# grant a lease with 10 second TTL
$ etcdctl lease grant 10
lease 32695410dcc0ca06 granted with TTL(10s)
# attach key foo to lease 32695410dcc0ca06
$ etcdctl put --lease=32695410dcc0ca06 foo bar
OK
```
## Revoke leases
Applications revoke leases by lease ID. Revoking a lease deletes all of its attached keys.
Suppose we finished the following sequence of operations:
```bash
$ etcdctl lease grant 10
lease 32695410dcc0ca06 granted with TTL(10s)
$ etcdctl put --lease=32695410dcc0ca06 foo bar
OK
```
Here is the command to revoke the same lease:
```bash
$ etcdctl lease revoke 32695410dcc0ca06
lease 32695410dcc0ca06 revoked
$ etcdctl get foo
# empty response since foo is deleted due to lease revocation
```
## Keep leases alive
Applications can keep a lease alive by refreshing its TTL so it does not expire.
Suppose we finished the following sequence of operations:
```bash
$ etcdctl lease grant 10
lease 32695410dcc0ca06 granted with TTL(10s)
```
Here is the command to keep the same lease alive:
```bash
$ etcdctl lease keep-alive 32695410dcc0ca06
lease 32695410dcc0ca06 keepalived with TTL(10)
lease 32695410dcc0ca06 keepalived with TTL(10)
lease 32695410dcc0ca06 keepalived with TTL(10)
...
```
## Get lease information
Applications may want to know about lease information, so that they can be renewed or to check if the lease still exists or it has expired. Applications may also want to know the keys to which a particular lease is attached.
Suppose we finished the following sequence of operations:
```bash
# grant a lease with 500 second TTL
$ etcdctl lease grant 500
lease 694d5765fc71500b granted with TTL(500s)
# attach key zoo1 to lease 694d5765fc71500b
$ etcdctl put zoo1 val1 --lease=694d5765fc71500b
OK
# attach key zoo2 to lease 694d5765fc71500b
$ etcdctl put zoo2 val2 --lease=694d5765fc71500b
OK
```
Here is the command to get information about the lease:
```bash
$ etcdctl lease timetolive 694d5765fc71500b
lease 694d5765fc71500b granted with TTL(500s), remaining(258s)
```
Here is the command to get information about the lease along with the keys attached with the lease:
etcd is designed to handle small key value pairs typical for metadata. Larger requests will work, but may increase the latency of other requests. For the time being, etcd guarantees to support RPC requests with up to 1MB of data. In the future, the size limit may be loosened or made configurable.
## Storage size limit
The default storage size limit is 2GB, configurable with `--quota-backend-bytes` flag; supports up to 8GB.
For testing and development deployments, the quickest and easiest way is to configure a local cluster. For a production deployment, refer to the [clustering][clustering] section.
## Local standalone cluster
### Starting a cluster
Run the following to deploy an etcd cluster as a standalone cluster:
```
$ ./etcd
...
```
If the `etcd` binary is not present in the current working directory, it might be located either at `$GOPATH/bin/etcd` or at `/usr/local/bin/etcd`. Run the command appropriately.
The running etcd member listens on `localhost:2379` for client requests.
### Interacting with the cluster
Use `etcdctl` to interact with the running cluster:
1. Configure the environment to have `ETCDCTL_API=3` so `etcdctl` uses the etcd API version 3 instead of defaulting to version 2.
```
# use API version 3
$ export ETCDCTL_API=3
```
2. Store an example key-value pair in the cluster:
```
$ ./etcdctl put foo bar
OK
```
If OK is printed, storing key-value pair is successful.
3. Retrieve the value of `foo`:
```
$ ./etcdctl get foo
bar
```
If `bar` is returned, interaction with the etcd cluster is working as expected.
## Local multi-member cluster
### Starting a cluster
A `Procfile` at the base of the etcd git repository is provided to easily configure a local multi-member cluster. To start a multi-member cluster, navigate to the root of the etcd source tree and perform the following:
1. Install `goreman` to control Procfile-based applications:
```
$ go get github.com/mattn/goreman
```
2. Start a cluster with `goreman` using etcd's stock Procfile:
```
$ goreman -f Procfile start
```
The members start running. They listen on `localhost:2379`, `localhost:22379`, and `localhost:32379` respectively for client requests.
### Interacting with the cluster
Use `etcdctl` to interact with the running cluster:
1. Configure the environment to have `ETCDCTL_API=3` so `etcdctl` uses the etcd API version 3 instead of defaulting to version 2.
```
# use API version 3
$ export ETCDCTL_API=3
```
2. Print the list of members:
```
$ etcdctl --write-out=table --endpoints=localhost:2379 member list
```
The list of etcd members are displayed as follows:
Restarting the member re-establish the connection. `etcdctl` will now be able to retrieve the key successfully. To learn more about interacting with etcd, read [interacting with etcd section][interacting].
Discovery service protocol helps new etcd member to discover all other members in cluster bootstrap phase using a shared discovery URL.
Discovery service protocol is _only_ used in cluster bootstrap phase, and cannot be used for runtime reconfiguration or cluster monitoring.
The protocol uses a new discovery token to bootstrap one _unique_ etcd cluster. Remember that one discovery token can represent only one etcd cluster. As long as discovery protocol on this token starts, even if it fails halfway, it must not be used to bootstrap another etcd cluster.
The rest of this article will walk through the discovery process with examples that correspond to a self-hosted discovery cluster. The public discovery service, discovery.etcd.io, functions the same way, but with a layer of polish to abstract away ugly URLs, generate UUIDs automatically, and provide some protections against excessive requests. At its core, the public discovery service still uses an etcd cluster as the data store as described in this document.
## Protocol workflow
The idea of discovery protocol is to use an internal etcd cluster to coordinate bootstrap of a new cluster. First, all new members interact with discovery service and help to generate the expected member list. Then each new member bootstraps its server using this list, which performs the same functionality as -initial-cluster flag.
In the following example workflow, we will list each step of protocol in curl format for ease of understanding.
By convention the etcd discovery protocol uses the key prefix `_etcd/registry`. If `http://example.com` hosts an etcd cluster for discovery service, a full URL to discovery keyspace will be `http://example.com/v2/keys/_etcd/registry`. We will use this as the URL prefix in the example.
### Creating a new discovery token
Generate a unique token that will identify the new cluster. This will be used as a unique prefix in discovery keyspace in the following steps. An easy way to do this is to use `uuidgen`:
```
UUID=$(uuidgen)
```
### Specifying the expected cluster size
The discovery token expects a cluster size that must be specified. The size is used by the discovery service to know when it has found all members that will initially form the cluster.
```
curl -X PUT http://example.com/v2/keys/_etcd/registry/${UUID}/_config/size -d value=${cluster_size}
```
Usually the cluster size is 3, 5 or 7. Check [optimal cluster size][cluster-size] for more details.
### Bringing up etcd processes
Given the discovery URL, use it as `-discovery` flag and bring up etcd processes. Every etcd process will follow this next few steps internally if given a `-discovery` flag.
### Registering itself
The first thing for etcd process is to register itself into the discovery URL as a member. This is done by creating member ID as a key in the discovery URL.
```
curl -X PUT http://example.com/v2/keys/_etcd/registry/${UUID}/${member_id}?prevExist=false -d value="${member_name}=${member_peer_url_1}&${member_name}=${member_peer_url_2}"
```
### Checking the status
It checks the expected cluster size and registration status in discovery URL, and decides what the next action is.
```
curl -X GET http://example.com/v2/keys/_etcd/registry/${UUID}/_config/size
curl -X GET http://example.com/v2/keys/_etcd/registry/${UUID}
```
If registered members are still not enough, it will wait for left members to appear.
If the number of registered members is bigger than the expected size N, it treats the first N registered members as the member list for the cluster. If the member itself is in the member list, the discovery procedure succeeds and it fetches all peers through the member list. If it is not in the member list, the discovery procedure finishes with the failure that the cluster has been full.
In etcd implementation, the member may check the cluster status even before registering itself. So it could fail quickly if the cluster has been full.
### Waiting for all members
The wait process is described in detail in the [etcd API documentation][api].
```
curl -X GET http://example.com/v2/keys/_etcd/registry/${UUID}?wait=true&waitIndex=${current_etcd_index}
```
It keeps waiting until finding all members.
## Public discovery service
CoreOS Inc. hosts a public discovery service at https://discovery.etcd.io/ , which provides some nice features for ease of use.
### Mask key prefix
Public discovery service will redirect `https://discovery.etcd.io/${UUID}` to etcd cluster behind for the key at `/v2/keys/_etcd/registry`. It masks register key prefix for short and readable discovery url.
### Get new token
```
GET /new
Sent query:
size=${cluster_size}
Possible status codes:
200 OK
400 Bad Request
200 Body:
generated discovery url
```
The generation process in the service follows the steps from [Creating a New Discovery Token][new-discovery-token] to [Specifying the Expected Cluster Size][expected-cluster-size].
### Check discovery status
```
GET /${UUID}
```
The status for this discovery token, including the machines that have been registered, can be checked by requesting the value of the UUID.
### Open-source repository
The repository is located at https://github.com/coreos/discovery.etcd.io. It could be used to build a custom discovery service.
etcd uses the [capnslog][capnslog] library for logging application output categorized into *levels*. A log message's level is determined according to these conventions:
* Error: Data has been lost, a request has failed for a bad reason, or a required resource has been lost
* Examples:
* A failure to allocate disk space for WAL
* Warning: (Hopefully) Temporary conditions that may cause errors, but may work fine. A replica disappearing (that may reconnect) is a warning.
* Examples:
* Failure to send raft message to a remote peer
* Failure to receive heartbeat message within the configured election timeout
* Notice: Normal, but important (uncommon) log information.
* Examples:
* Add a new node into the cluster
* Add a new user into auth subsystem
* Info: Normal, working log information, everything is fine, but helpful notices for auditing or common operations.
* Examples:
* Startup configuration
* Start to do snapshot
* Debug: Everything is still fine, but even common operations may be logged, and less helpful but more quantity of notices.
The guide talks about how to release a new version of etcd.
The procedure includes some manual steps for sanity checking, but it can probably be further scripted. Please keep this document up-to-date if making changes to the release process.
## Prepare release
Set desired version as environment variable for following steps. Here is an example to release 2.3.0:
```
export VERSION=v2.3.0
export PREV_VERSION=v2.2.5
```
All releases version numbers follow the format of [semantic versioning 2.0.0](http://semver.org/).
### Major, minor version release, or its pre-release
- Ensure the relevant milestone on GitHub is complete. All referenced issues should be closed, or moved elsewhere.
- Remove this release from [roadmap](https://github.com/coreos/etcd/blob/master/ROADMAP.md), if necessary.
- Ensure the latest upgrade documentation is available.
- Bump [hardcoded MinClusterVerion in the repository](https://github.com/coreos/etcd/blob/master/version/version.go#L29), if necessary.
- Add feature capability maps for the new version, if necessary.
### Patch version release
- To request a backport, devlopers submit cherrypick PRs targeting the release branch. The commits should not include merge commits. The commits should be restricted to bug fixes and security patches.
- The cherrypick PRs should target the appropriate release branch (`base:release-<major>-<minor>`). `hack/patch/cherrypick.sh` may be used to automatically generate cherrypick PRs.
- The release patch manager reviews the cherrypick PRs. Please discuss carefully what is backported to the patch release. Each patch release should be strictly better than it's predecessor.
- The release patch manager will cherry-pick these commits starting from the oldest one into stable branch.
## Write release note
- Write introduction for the new release. For example, what major bug we fix, what new features we introduce or what performance improvement we make.
- Put `[GH XXXX]` at the head of change line to reference Pull Request that introduces the change. Moreover, add a link on it to jump to the Pull Request.
- Find PRs with `release-note` label and explain them in `NEWS` file, as a straightforward summary of changes for end-users.
## Tag version
- Bump [hardcoded Version in the repository](https://github.com/coreos/etcd/blob/master/version/version.go#L30) to the latest version `${VERSION}`.
- Ensure all tests on CI system are passed.
- Manually check etcd is buildable in Linux, Darwin and Windows.
- Manually check upgrade etcd cluster of previous minor version works well.
- Manually check new features work well.
- Add a signed tag through `git tag -s ${VERSION}`.
- Sanity check tag correctness through `git show tags/$VERSION`.
- Push the tag to GitHub through `git push origin tags/$VERSION`. This assumes `origin` corresponds to "https://github.com/coreos/etcd".
It generates all release binaries and images under directory ./release.
## Sign binaries, images, and source code
etcd project key must be used to sign the generated binaries and images.`$SUBKEYID` is the key ID of etcd project Yubikey. Connect the key and run `gpg2 --card-status` to get the ID.
The following commands are used for public release sign:
```
cd release
for i in etcd-*{.zip,.tar.gz,.aci}; do gpg2 --default-key $SUBKEYID --armor --output ${i}.asc --detach-sign ${i}; done
for i in etcd-*{.zip,.tar.gz,.aci}; do gpg2 --verify ${i}.asc ${i}; done
- Add `latest` tag to the new image on [gcr.io](https://console.cloud.google.com/gcr/images/etcd-development/GLOBAL/etcd?project=etcd-development&authuser=1) if this is a stable release.
- Create new stable branch through `git push origin ${VERSION_MAJOR}.${VERSION_MINOR}` if this is a major stable release. This assumes `origin` corresponds to "https://github.com/coreos/etcd".
- Bump [hardcoded Version in the repository](https://github.com/coreos/etcd/blob/master/version/version.go#L30) to the version `${VERSION}+git`.
The etcd performance benchmarks run etcd on 8 vCPU, 16GB RAM, 50GB SSD GCE instances, but any relatively modern machine with low latency storage and a few gigabytes of memory should suffice for most use cases. Applications with large v2 data stores will require more memory than a large v3 data store since data is kept in anonymous memory instead of memory mapped from a file. For running etcd on a cloud provider, see the [Example hardware configuration][example-hardware-configurations] documentation.
## Download the pre-built binary
The easiest way to get etcd is to use one of the pre-built release binaries which are available for OSX, Linux, Windows, appc, and Docker. Instructions for using these binaries are on the [GitHub releases page][github-release].
## Build the latest version
For those wanting to try the very latest version, build etcd from the `master` branch. [Go](https://golang.org/) version 1.9+ is required to build the latest version of etcd. To ensure etcd is built against well-tested libraries, etcd vendors its dependencies for official release binaries. However, etcd's vendoring is also optional to avoid potential import conflicts when embedding the etcd server or using the etcd client.
To build `etcd` from the `master` branch without a `GOPATH` using the official `build` script:
```sh
$ git clone https://github.com/coreos/etcd.git
$ cd etcd
$ ./build
```
To build a vendored `etcd` from the `master` branch via `go get`:
```sh
# GOPATH should be set
$ echo$GOPATH
/Users/example/go
$ go get github.com/coreos/etcd/cmd/etcd
```
To build `etcd` from the `master` branch without vendoring (may not build due to upstream conflicts):
```sh
# GOPATH should be set
$ echo$GOPATH
/Users/example/go
$ go get github.com/coreos/etcd
```
## Test the installation
Check the etcd binary is built correctly by starting etcd and setting a key.
### Starting etcd
If etcd is built without using GOPATH, run the following:
etcd is a distributed key-value store designed to reliably and quickly preserve and provide access to critical data. It enables reliable distributed coordination through distributed locking, leader elections, and write barriers. An etcd cluster is intended for high availability and permanent data storage and retrieval.
## Getting started
New etcd users and developers should get started by [downloading and building][download_build] etcd. After getting etcd, follow this [quick demo][demo] to see the basics of creating and working with an etcd cluster.
## Developing with etcd
The easiest way to get started using etcd as a distributed key-value store is to [set up a local cluster][local_cluster].
- [Setting up local clusters][local_cluster]
- [Interacting with etcd][interacting]
- gRPC [etcd core][api_ref] and [etcd concurrency][api_concurrency_ref] API references
- [HTTP JSON API through the gRPC gateway][api_grpc_gateway]
- [gRPC naming and discovery][grpc_naming]
- [Client][namespace_client] and [proxy][namespace_proxy] namespacing
- [Embedding etcd][embed_etcd]
- [Experimental features and APIs][experimental]
- [System limits][system-limit]
## Operating etcd clusters
Administrators who need a fault-tolerant etcd cluster for either development or production should begin with a [cluster on multiple machines][clustering].
### Do clients have to send requests to the etcd leader?
[Raft][raft] is leader-based; the leader handles all client requests which need cluster consensus. However, the client does not need to know which node is the leader. Any request that requires consensus sent to a follower is automatically forwarded to the leader. Requests that do not require consensus (e.g., serialized reads) can be processed by any cluster member.
## Configuration
### What is the difference between listen-<client,peer>-urls, advertise-client-urls or initial-advertise-peer-urls?
`listen-client-urls` and `listen-peer-urls` specify the local addresses etcd server binds to for accepting incoming connections. To listen on a port for all interfaces, specify `0.0.0.0` as the listen IP address.
`advertise-client-urls` and `initial-advertise-peer-urls` specify the addresses etcd clients or other etcd members should use to contact the etcd server. The advertise addresses must be reachable from the remote machines. Do not advertise addresses like `localhost` or `0.0.0.0` for a production setup since these addresses are unreachable from remote machines.
### Why doesn't changing `--listen-peer-urls` or `--initial-advertise-peer-urls` update the advertised peer URLs in `etcdctl member list`?
A member's advertised peer URLs come from `--initial-advertise-peer-urls` on initial cluster boot. Changing the listen peer URLs or the initial advertise peers after booting the member won't affect the exported advertise peer URLs since changes must go through quorum to avoid membership configuration split brain. Use `etcdctl member update` to update a member's peer URLs.
## Deployment
### System requirements
Since etcd writes data to disk, SSD is highly recommended. To prevent performance degradation or unintentionally overloading the key-value store, etcd enforces a 2GB default storage size quota, configurable up to 8GB. To avoid swapping or running out of memory, the machine should have at least as much RAM to cover the quota. At CoreOS, an etcd cluster is usually deployed on dedicated CoreOS Container Linux machines with dual-core processors, 2GB of RAM, and 80GB of SSD *at the very least*. **Note that performance is intrinsically workload dependent; please test before production deployment**. See [hardware][hardware-setup] for more recommendations.
Most stable production environment is Linux operating system with amd64 architecture; see [supported platform][supported-platform] for more.
### Why an odd number of cluster members?
An etcd cluster needs a majority of nodes, a quorum, to agree on updates to the cluster state. For a cluster with n members, quorum is (n/2)+1. For any odd-sized cluster, adding one node will always increase the number of nodes necessary for quorum. Although adding a node to an odd-sized cluster appears better since there are more machines, the fault tolerance is worse since exactly the same number of nodes may fail without losing quorum but there are more nodes that can fail. If the cluster is in a state where it can't tolerate any more failures, adding a node before removing nodes is dangerous because if the new node fails to register with the cluster (e.g., the address is misconfigured), quorum will be permanently lost.
### What is maximum cluster size?
Theoretically, there is no hard limit. However, an etcd cluster probably should have no more than seven nodes. [Google Chubby lock service][chubby], similar to etcd and widely deployed within Google for many years, suggests running five nodes. A 5-member etcd cluster can tolerate two member failures, which is enough in most cases. Although larger clusters provide better fault tolerance, the write performance suffers because data must be replicated across more machines.
### What is failure tolerance?
An etcd cluster operates so long as a member quorum can be established. If quorum is lost through transient network failures (e.g., partitions), etcd automatically and safely resumes once the network recovers and restores quorum; Raft enforces cluster consistency. For power loss, etcd persists the Raft log to disk; etcd replays the log to the point of failure and resumes cluster participation. For permanent hardware failure, the node may be removed from the cluster through [runtime reconfiguration][runtime reconfiguration].
It is recommended to have an odd number of members in a cluster. An odd-size cluster tolerates the same number of failures as an even-size cluster but with fewer nodes. The difference can be seen by comparing even and odd sized clusters:
| Cluster Size | Majority | Failure Tolerance |
|:-:|:-:|:-:|
| 1 | 1 | 0 |
| 2 | 2 | 0 |
| 3 | 2 | 1 |
| 4 | 3 | 1 |
| 5 | 3 | 2 |
| 6 | 4 | 2 |
| 7 | 4 | 3 |
| 8 | 5 | 3 |
| 9 | 5 | 4 |
Adding a member to bring the size of cluster up to an even number doesn't buy additional fault tolerance. Likewise, during a network partition, an odd number of members guarantees that there will always be a majority partition that can continue to operate and be the source of truth when the partition ends.
### Does etcd work in cross-region or cross data center deployments?
Deploying etcd across regions improves etcd's fault tolerance since members are in separate failure domains. The cost is higher consensus request latency from crossing data center boundaries. Since etcd relies on a member quorum for consensus, the latency from crossing data centers will be somewhat pronounced because at least a majority of cluster members must respond to consensus requests. Additionally, cluster data must be replicated across all peers, so there will be bandwidth cost as well.
With longer latencies, the default etcd configuration may cause frequent elections or heartbeat timeouts. See [tuning] for adjusting timeouts for high latency deployments.
## Operation
### How to backup a etcd cluster?
etcdctl provides a `snapshot` command to create backups. See [backup][backup] for more details.
### Should I add a member before removing an unhealthy member?
When replacing an etcd node, it's important to remove the member first and then add its replacement.
etcd employs distributed consensus based on a quorum model; (n+1)/2 members, a majority, must agree on a proposal before it can be committed to the cluster. These proposals include key-value updates and membership changes. This model totally avoids any possibility of split brain inconsistency. The downside is permanent quorum loss is catastrophic.
How this applies to membership: If a 3-member cluster has 1 downed member, it can still make forward progress because the quorum is 2 and 2 members are still live. However, adding a new member to a 3-member cluster will increase the quorum to 3 because 3 votes are required for a majority of 4 members. Since the quorum increased, this extra member buys nothing in terms of fault tolerance; the cluster is still one node failure away from being unrecoverable.
Additionally, that new member is risky because it may turn out to be misconfigured or incapable of joining the cluster. In that case, there's no way to recover quorum because the cluster has two members down and two members up, but needs three votes to change membership to undo the botched membership addition. etcd will by default reject member add attempts that could take down the cluster in this manner.
On the other hand, if the downed member is removed from cluster membership first, the number of members becomes 2 and the quorum remains at 2. Following that removal by adding a new member will also keep the quorum steady at 2. So, even if the new node can't be brought up, it's still possible to remove the new member through quorum on the remaining live members.
### Why won't etcd accept my membership changes?
etcd sets `strict-reconfig-check` in order to reject reconfiguration requests that would cause quorum loss. Abandoning quorum is really risky (especially when the cluster is already unhealthy). Although it may be tempting to disable quorum checking if there's quorum loss to add a new member, this could lead to full fledged cluster inconsistency. For many applications, this will make the problem even worse ("disk geometry corruption" being a candidate for most terrifying).
### Why does etcd lose its leader from disk latency spikes?
This is intentional; disk latency is part of leader liveness. Suppose the cluster leader takes a minute to fsync a raft log update to disk, but the etcd cluster has a one second election timeout. Even though the leader can process network messages within the election interval (e.g., send heartbeats), it's effectively unavailable because it can't commit any new proposals; it's waiting on the slow disk. If the cluster frequently loses its leader due to disk latencies, try [tuning][tuning] the disk settings or etcd time parameters.
### What does the etcd warning "request ignored (cluster ID mismatch)" mean?
Every new etcd cluster generates a new cluster ID based on the initial cluster configuration and a user-provided unique `initial-cluster-token` value. By having unique cluster ID's, etcd is protected from cross-cluster interaction which could corrupt the cluster.
Usually this warning happens after tearing down an old cluster, then reusing some of the peer addresses for the new cluster. If any etcd process from the old cluster is still running it will try to contact the new cluster. The new cluster will recognize a cluster ID mismatch, then ignore the request and emit this warning. This warning is often cleared by ensuring peer addresses among distinct clusters are disjoint.
### What does "mvcc: database space exceeded" mean and how do I fix it?
The [multi-version concurrency control][api-mvcc] data model in etcd keeps an exact history of the keyspace. Without periodically compacting this history (e.g., by setting `--auto-compaction`), etcd will eventually exhaust its storage space. If etcd runs low on storage space, it raises a space quota alarm to protect the cluster from further writes. So long as the alarm is raised, etcd responds to write requests with the error `mvcc: database space exceeded`.
To recover from the low space quota alarm:
1. [Compact][maintenance-compact] etcd's history.
2. [Defragment][maintenance-defragment] every etcd endpoint.
3. [Disarm][maintenance-disarm] the alarm.
## Performance
### How should I benchmark etcd?
Try the [benchmark] tool. Current [benchmark results][benchmark-result] are available for comparison.
### What does the etcd warning "apply entries took too long" mean?
After a majority of etcd members agree to commit a request, each etcd server applies the request to its data store and persists the result to disk. Even with a slow mechanical disk or a virtualized network disk, such as Amazon’s EBS or Google’s PD, applying a request should normally take fewer than 50 milliseconds. If the average apply duration exceeds 100 milliseconds, etcd will warn that entries are taking too long to apply.
Usually this issue is caused by a slow disk. The disk could be experiencing contention among etcd and other applications, or the disk is too simply slow (e.g., a shared virtualized disk). To rule out a slow disk from causing this warning, monitor [backend_commit_duration_seconds][backend_commit_metrics] (p99 duration should be less than 25ms) to confirm the disk is reasonably fast. If the disk is too slow, assigning a dedicated disk to etcd or using faster disk will typically solve the problem.
The second most common cause is CPU starvation. If monitoring of the machine’s CPU usage shows heavy utilization, there may not be enough compute capacity for etcd. Moving etcd to dedicated machine, increasing process resource isolation cgroups, or renicing the etcd server process into a higher priority can usually solve the problem.
Expensive user requests which access too many keys (e.g., fetching the entire keyspace) can also cause long apply latencies. Accessing fewer than a several hundred keys per request, however, should always be performant.
If none of the above suggestions clear the warnings, please [open an issue][new_issue] with detailed logging, monitoring, metrics and optionally workload information.
### What does the etcd warning "failed to send out heartbeat on time" mean?
etcd uses a leader-based consensus protocol for consistent data replication and log execution. Cluster members elect a single leader, all other members become followers. The elected leader must periodically send heartbeats to its followers to maintain its leadership. Followers infer leader failure if no heartbeats are received within an election interval and trigger an election. If a leader doesn’t send its heartbeats in time but is still running, the election is spurious and likely caused by insufficient resources. To catch these soft failures, if the leader skips two heartbeat intervals, etcd will warn it failed to send a heartbeat on time.
Usually this issue is caused by a slow disk. Before the leader sends heartbeats attached with metadata, it may need to persist the metadata to disk. The disk could be experiencing contention among etcd and other applications, or the disk is too simply slow (e.g., a shared virtualized disk). To rule out a slow disk from causing this warning, monitor [wal_fsync_duration_seconds][wal_fsync_duration_seconds] (p99 duration should be less than 10ms) to confirm the disk is reasonably fast. If the disk is too slow, assigning a dedicated disk to etcd or using faster disk will typically solve the problem.
The second most common cause is CPU starvation. If monitoring of the machine’s CPU usage shows heavy utilization, there may not be enough compute capacity for etcd. Moving etcd to dedicated machine, increasing process resource isolation with cgroups, or renicing the etcd server process into a higher priority can usually solve the problem.
A slow network can also cause this issue. If network metrics among the etcd machines shows long latencies or high drop rate, there may not be enough network capacity for etcd. Moving etcd members to a less congested network will typically solve the problem. However, if the etcd cluster is deployed across data centers, long latency between members is expected. For such deployments, tune the `heartbeat-interval` configuration to roughly match the round trip time between the machines, and the `election-timeout` configuration to be at least 5 * `heartbeat-interval`. See [tuning documentation][tuning] for detailed information.
If none of the above suggestions clear the warnings, please [open an issue][new_issue] with detailed logging, monitoring, metrics and optionally workload information.
### What does the etcd warning "snapshotting is taking more than x seconds to finish ..." mean?
etcd sends a snapshot of its complete key-value store to refresh slow followers and for [backups][backup]. Slow snapshot transfer times increase MTTR; if the cluster is ingesting data with high throughput, slow followers may livelock by needing a new snapshot before finishing receiving a snapshot. To catch slow snapshot performance, etcd warns when sending a snapshot takes more than thirty seconds and exceeds the expected transfer time for a 1Gbps connection.
This document is meant to give an overview of the etcd3 API's central design. It is by no means all encompassing, but intended to focus on the basic ideas needed to understand etcd without the distraction of less common API calls. All etcd3 API's are defined in [gRPC services][grpc-service], which categorize remote procedure calls (RPCs) understood by the etcd server. A full listing of all etcd RPCs are documented in markdown in the [gRPC API listing][grpc-api].
## gRPC Services
Every API request sent to an etcd server is a gRPC remote procedure call. RPCs in etcd3 are categorized based on functionality into services.
Services important for dealing with etcd's key space include:
* KV - Creates, updates, fetches, and deletes key-value pairs.
* Watch - Monitors changes to keys.
* Lease - Primitives for consuming client keep-alive messages.
Services which manage the cluster itself include:
* Auth - Role based authentication mechanism for authenticating users.
* Cluster - Provides membership information and configuration facilities.
* Maintenance - Takes recovery snapshots, defragments the store, and returns per-member status information.
### Requests and Responses
All RPCs in etcd3 follow the same format. Each RPC has a function `Name` which takes `NameRequest` as an argument and returns `NameResponse` as a response. For example, here is the `Range` RPC description:
```protobuf
serviceKV{
Range(RangeRequest)returns(RangeResponse)
...
}
```
### Response header
All Responses from etcd API have an attached response header which includes cluster metadata for the response:
```proto
messageResponseHeader{
uint64cluster_id=1;
uint64member_id=2;
int64revision=3;
uint64raft_term=4;
}
```
* Cluster_ID - the ID of the cluster generating the response.
* Member_ID - the ID of the member generating the response.
* Revision - the revision of the key-value store when generating the response.
* Raft_Term - the Raft term of the member when generating the response.
An application may read the Cluster_ID (Member_ID) field to ensure it is communicating with the intended cluster (member).
Applications can use the `Revision` to know the latest revision of the key-value store. This is especially useful when applications specify a historical revision to make time `travel query` and wish to know the latest revision at the time of the request.
Applications can use `Raft_Term` to detect when the cluster completes a new leader election.
## Key-Value API
The Key-Value API manipulates key-value pairs stored inside etcd. The majority of requests made to etcd are usually key-value requests.
### System primitives
### Key-Value pair
A key-value pair is the smallest unit that the key-value API can manipulate. Each key-value pair has a number of fields, defined in [protobuf format][kv-proto]:
```protobuf
messageKeyValue{
byteskey=1;
int64create_revision=2;
int64mod_revision=3;
int64version=4;
bytesvalue=5;
int64lease=6;
}
```
* Key - key in bytes. An empty key is not allowed.
* Value - value in bytes.
* Version - version is the version of the key. A deletion resets the version to zero and any modification of the key increases its version.
* Create_Revision - revision of the last creation on the key.
* Mod_Revision - revision of the last modification on the key.
* Lease - the ID of the lease attached to the key. If lease is 0, then no lease is attached to the key.
In addition to just the key and value, etcd attaches additional revision metadata as part of the key message. This revision information orders keys by time of creation and modification, which is useful for managing concurrency for distributed synchronization. The etcd client's [distributed shared locks][locks] use the creation revision to wait for lock ownership. Similarly, the modification revision is used for detecting [software transactional memory][STM] read set conflicts and waiting on [leader election][elections] updates.
#### Revisions
etcd maintains a 64-bit cluster-wide counter, the store revision, that is incremented each time the key space is modified. The revision serves as a global logical clock, sequentially ordering all updates to the store. The change represented by a new revisions is incremental; the data associated with a revision is the data that changed the store. Internally, a new revision means writing the changes to the backend's B+tree, keyed by the incremented revision.
Revisions become more valuable when taking considering etcd3's [multi-version concurrency control][mvcc] backend. The MVCC model means that the key-value store can be viewed from past revisions since historical key revisions are retained. The retention policy for this history can be configured by cluster administrators for fine-grained storage management; usually etcd3 discards old revisions of keys on a timer. A typical etcd3 cluster retains superseded key data for hours. This also buys reliable handling for long client disconnection, not just transient network disruptions: watchers simply resume from the last observed historical revision. Similarly, to read from the store at a particular point-in-time, read requests can be tagged with a revision to return keys from a view of the key space at the point in time that revision was committed.
#### Key ranges
The etcd3 data model indexes all keys over a flat binary key space. This differs from other key-value store systems that use a hierarchical system of organizing keys into directories. Instead of listing keys by directory, keys are listed by key intervals `[a, b)`.
These intervals are often referred to as "ranges" in etcd3. Operations over ranges are more powerful than operations on directories. Like a hierarchical store, intervals support single key lookups via `[a, a+1)` (e.g., ['a', 'a\x00') looks up 'a') and directory lookups by encoding keys by directory depth. In addition to those operations, intervals can also encode prefixes; for example the interval `['a', 'b')` looks up all keys prefixed by the string 'a'.
By convention, ranges for a Request are denoted by the fields `key` and `range_end`. The `key` field is the first key of the range and should be non-empty. The `range_end` is the key following the last key of the range. If `range_end` is not given or empty, the range is defined to contain only the key argument. If `range_end` is `key` plus one (e.g., "aa"+1 == "ab", "a\xff"+1 == "b"), then the range represents all keys prefixed with key. If both `key` and `range_end` are '\0', then range represents all keys. If `range_end` is '\0', the range is all keys greater than or equal to the key argument.
### Range
Keys are fetched from the key-value store using the `Range` API call, which takes a `RangeRequest`:
```protobuf
messageRangeRequest{
enumSortOrder{
NONE=0;// default, no sorting
ASCEND=1;// lowest target value first
DESCEND=2;// highest target value first
}
enumSortTarget{
KEY=0;
VERSION=1;
CREATE=2;
MOD=3;
VALUE=4;
}
byteskey=1;
bytesrange_end=2;
int64limit=3;
int64revision=4;
SortOrdersort_order=5;
SortTargetsort_target=6;
boolserializable=7;
boolkeys_only=8;
boolcount_only=9;
int64min_mod_revision=10;
int64max_mod_revision=11;
int64min_create_revision=12;
int64max_create_revision=13;
}
```
* Key, Range_End - The key range to fetch.
* Limit - the maximum number of keys returned for the request. When limit is set to 0, it is treated as no limit.
* Revision - the point-in-time of the key-value store to use for the range. If revision is less or equal to zero, the range is over the latest key-value store If the revision is compacted, ErrCompacted is returned as a response.
* Sort_Order - the ordering for sorted requests.
* Sort_Target - the key-value field to sort.
* Serializable - sets the range request to use serializable member-local reads. By default, Range is linearizable; it reflects the current consensus of the cluster. For better performance and availability, in exchange for possible stale reads, a serializable range request is served locally without needing to reach consensus with other nodes in the cluster.
* Keys_Only - return only the keys and not the values.
* Count_Only - return only the count of the keys in the range.
* Min_Mod_Revision - the lower bound for key mod revisions; filters out lesser mod revisions.
* Max_Mod_Revision - the upper bound for key mod revisions; filters out greater mod revisions.
* Min_Create_Revision - the lower bound for key create revisions; filters out lesser create revisions.
* Max_Create_Revision - the upper bound for key create revisions; filters out greater create revisions.
The client receives a `RangeResponse` message from the `Range` call:
```protobuf
messageRangeResponse{
ResponseHeaderheader=1;
repeatedmvccpb.KeyValuekvs=2;
boolmore=3;
int64count=4;
}
```
* Kvs - the list of key-value pairs matched by the range request. When `Count_Only` is set, `Kvs` is empty.
* More - indicates if there are more keys to return in the requested range if `limit` is set.
* Count - the total number of keys satisfying the range request.
### Put
Keys are saved into the key-value store by issuing a `Put` call, which takes a `PutRequest`:
```protobuf
messagePutRequest{
byteskey=1;
bytesvalue=2;
int64lease=3;
boolprev_kv=4;
boolignore_value=5;
boolignore_lease=6;
}
```
* Key - the name of the key to put into the key-value store.
* Value - the value, in bytes, to associate with the key in the key-value store.
* Lease - the lease ID to associate with the key in the key-value store. A lease value of 0 indicates no lease.
* Prev_Kv - when set, responds with the key-value pair data before the update from this `Put` request.
* Ignore_Value - when set, update the key without changing its current value. Returns an error if the key does not exist.
* Ignore_Lease - when set, update the key without changing its current lease. Returns an error if the key does not exist.
The client receives a `PutResponse` message from the `Put` call:
```protobuf
messagePutResponse{
ResponseHeaderheader=1;
mvccpb.KeyValueprev_kv=2;
}
```
* Prev_Kv - the key-value pair overwritten by the `Put`, if `Prev_Kv` was set in the `PutRequest`.
### Delete Range
Ranges of keys are deleted using the `DeleteRange` call, which takes a `DeleteRangeRequest`:
```protobuf
messageDeleteRangeRequest{
byteskey=1;
bytesrange_end=2;
boolprev_kv=3;
}
```
* Key, Range_End - The key range to delete.
* Prev_Kv - when set, return the contents of the deleted key-value pairs.
The client receives a `DeleteRangeResponse` message from the `DeleteRange` call:
```protobuf
messageDeleteRangeResponse{
ResponseHeaderheader=1;
int64deleted=2;
repeatedmvccpb.KeyValueprev_kvs=3;
}
```
* Deleted - number of keys deleted.
* Prev_Kv - a list of all key-value pairs deleted by the DeleteRange operation.
### Transaction
A transaction is an atomic If/Then/Else construct over the key-value store. It provides a primitive for grouping requests together in atomic blocks (i.e., then/else) whose execution is guarded (i.e., if) based on the contents of the key-value store. Transactions can be used for protecting keys from unintended concurrent updates, building compare-and-swap operations, and developing higher-level concurrency control.
A transaction can atomically process multiple requests in a single request. For modifications to the key-value store, this means the store's revision is incremented only once for the transaction and all events generated by the transaction will have the same revision. However, modifications to the same key multiple times within a single transaction are forbidden.
All transactions are guarded by a conjunction of comparisons, similar to an "If" statement. Each comparison checks a single key in the store. It may check for the absence or presence of a value, compare with a given value, or check a key's revision or version. Two different comparisons may apply to the same or different keys. All comparisons are applied atomically; if all comparisons are true, the transaction is said to succeed and etcd applies the transaction's then / `success` request block, otherwise it is said to fail and applies the else / `failure` request block.
Each comparison is encoded as a `Compare` message:
```protobuf
messageCompare{
enumCompareResult{
EQUAL=0;
GREATER=1;
LESS=2;
NOT_EQUAL=3;
}
enumCompareTarget{
VERSION=0;
CREATE=1;
MOD=2;
VALUE=3;
}
CompareResultresult=1;
// target is the key-value field to inspect for the comparison.
CompareTargettarget=2;
// key is the subject key for the comparison operation.
byteskey=3;
oneoftarget_union{
int64version=4;
int64create_revision=5;
int64mod_revision=6;
bytesvalue=7;
}
}
```
* Result - the kind of logical comparison operation (e.g., equal, less than, etc).
* Target - the key-value field to be compared. Either the key's version, create revision, modification revision, or value.
* Key - the key for the comparison.
* Target_Union - the user-specified data for the comparison.
After processing the comparison block, the transaction applies a block of requests. A block is a list of `RequestOp` messages:
```protobuf
messageRequestOp{
// request is a union of request types accepted by a transaction.
oneofrequest{
RangeRequestrequest_range=1;
PutRequestrequest_put=2;
DeleteRangeRequestrequest_delete_range=3;
}
}
```
* Request_Range - a `RangeRequest`.
* Request_Put - a `PutRequest`. The keys must be unique. It may not share keys with any other Puts or Deletes.
* Request_Delete_Range - a `DeleteRangeRequest`. It may not share keys with any Puts or Deletes requests.
All together, a transaction is issued with a `Txn` API call, which takes a `TxnRequest`:
```protobuf
messageTxnRequest{
repeatedComparecompare=1;
repeatedRequestOpsuccess=2;
repeatedRequestOpfailure=3;
}
```
* Compare - A list of predicates representing a conjunction of terms for guarding the transaction.
* Success - A list of requests to process if all compare tests evaluate to true.
* Failure - A list of requests to process if any compare test evaluates to false.
The client receives a `TxnResponse` message from the `Txn` call:
```protobuf
messageTxnResponse{
ResponseHeaderheader=1;
boolsucceeded=2;
repeatedResponseOpresponses=3;
}
```
* Succeeded - Whether `Compare` evaluated to true or false.
* Responses - A list of responses corresponding to the results from applying the `Success` block if succeeded is true or the `Failure` if succeeded is false.
The `Responses` list corresponds to the results from the applied `RequestOp` list, with each response encoded as a `ResponseOp`:
```protobuf
messageResponseOp{
oneofresponse{
RangeResponseresponse_range=1;
PutResponseresponse_put=2;
DeleteRangeResponseresponse_delete_range=3;
}
}
```
## Watch API
The Watch API provides an event-based interface for asynchronously monitoring changes to keys. An etcd3 watch waits for changes to keys by continuously watching from a given revision, either current or historical, and streams key updates back to the client.
### Events
Every change to every key is represented with `Event` messages. An `Event` message provides both the update's data and the type of update:
```protobuf
messageEvent{
enumEventType{
PUT=0;
DELETE=1;
}
EventTypetype=1;
KeyValuekv=2;
KeyValueprev_kv=3;
}
```
* Type - The kind of event. A PUT type indicates new data has been stored to the key. A DELETE indicates the key was deleted.
* KV - The KeyValue associated with the event. A PUT event contains current kv pair. A PUT event with kv.Version=1 indicates the creation of a key. A DELETE event contains the deleted key with its modification revision set to the revision of deletion.
* Prev_KV - The key-value pair for the key from the revision immediately before the event. To save bandwidth, it is only filled out if the watch has explicitly enabled it.
### Watch streams
Watches are long-running requests and use gRPC streams to stream event data. A watch stream is bi-directional; the client writes to the stream to establish watches and reads to receive watch event. A single watch stream can multiplex many distinct watches by tagging events with per-watch identifiers. This multiplexing helps reducing the memory footprint and connection overhead on the core etcd cluster.
Watches make three guarantees about events:
* Ordered - events are ordered by revision; an event will never appear on a watch if it precedes an event in time that has already been posted.
* Reliable - a sequence of events will never drop any subsequence of events; if there are events ordered in time as a <b<c,thenifthewatchreceiveseventsaandc,itisguaranteedtoreceiveb.
etcd is a consistent and durable key value store with [mini-transaction][txn] support. The key value store is exposed through the KV APIs. etcd tries to ensure the strongest consistency and durability guarantees for a distributed system. This specification enumerates the KV API guarantees made by etcd.
### APIs to consider
* Read APIs
* range
* watch
* Write APIs
* put
* delete
* Combination (read-modify-write) APIs
* txn
### etcd specific definitions
#### Operation completed
An etcd operation is considered complete when it is committed through consensus, and therefore “executed” -- permanently stored -- by the etcd storage engine. The client knows an operation is completed when it receives a response from the etcd server. Note that the client may be uncertain about the status of an operation if it times out, or there is a network disruption between the client and the etcd member. etcd may also abort operations when there is a leader election. etcd does not send `abort` responses to clients’ outstanding requests in this event.
#### Revision
An etcd operation that modifies the key value store is assigned a single increasing revision. A transaction operation might modify the key value store multiple times, but only one revision is assigned. The revision attribute of a key value pair that was modified by the operation has the same value as the revision of the operation. The revision can be used as a logical clock for key value store. A key value pair that has a larger revision is modified after a key value pair with a smaller revision. Two key value pairs that have the same revision are modified by an operation "concurrently".
### Guarantees provided
#### Atomicity
All API requests are atomic; an operation either completes entirely or not at all. For watch requests, all events generated by one operation will be in one watch response. Watch never observes partial events for a single operation.
#### Consistency
All API calls ensure [sequential consistency][seq_consistency], the strongest consistency guarantee available from distributed systems. No matter which etcd member server a client makes requests to, a client reads the same events in the same order. If two members complete the same number of operations, the state of the two members is consistent.
For watch operations, etcd guarantees to return the same value for the same key across all members for the same revision. For range operations, etcd has a similar guarantee for [linearized][Linearizability] access; serialized access may be behind the quorum state, so that the later revision is not yet available.
As with all distributed systems, it is impossible for etcd to ensure [strict consistency][strict_consistency]. etcd does not guarantee that it will return to a read the “most recent” value (as measured by a wall clock when a request is completed) available on any cluster member.
#### Isolation
etcd ensures [serializable isolation][serializable_isolation], which is the highest isolation level available in distributed systems. Read operations will never observe any intermediate data.
#### Durability
Any completed operations are durable. All accessible data is also durable data. A read will never return data that has not been made durable.
#### Linearizability
Linearizability (also known as Atomic Consistency or External Consistency) is a consistency level between strict consistency and sequential consistency.
For linearizability, suppose each operation receives a timestamp from a loosely synchronized global clock. Operations are linearized if and only if they always complete as though they were executed in a sequential order and each operation appears to complete in the order specified by the program. Likewise, if an operation’s timestamp precedes another, that operation must also precede the other operation in the sequence.
For example, consider a client completing a write at time point 1 (*t1*). A client issuing a read at *t2* (for *t2* > *t1*) should receive a value at least as recent as the previous write, completed at *t1*. However, the read might actually complete only by *t3*, and the returned value, current at *t2* when the read began, might be "stale" by *t3*.
etcd does not ensure linearizability for watch operations. Users are expected to verify the revision of watch responses to ensure correct ordering.
etcd ensures linearizability for all other operations by default. Linearizability comes with a cost, however, because linearized requests must go through the Raft consensus process. To obtain lower latencies and higher throughput for read requests, clients can configure a request’s consistency mode to `serializable`, which may access stale data with respect to quorum, but removes the performance penalty of linearized accesses' reliance on live consensus.
The v3 protocol uses gRPC as its transport instead of a RESTful interface like v2. This new protocol provides an opportunity to iterate on and improve the v2 design. For example, v3 auth has connection based authentication, rather than v2's slower per-request authentication. Additionally, v2 auth's semantics tend to be unwieldy in practice with respect to reasoning about consistency, which will be described in the next sections. For v3, there is a well-defined description and implementation of the authentication mechanism which fixes the deficiencies in the v2 auth system.
### Functionality requirements
* Per connection authentication, not per request
* User ID + password based authentication implemented for the gRPC API
* Authentication must be refreshed after auth policy changes
* Its functionality should be as simple and useful as v2
* v3 provides a flat key space, unlike the directory structure of v2. Permission checking will be provided as interval matching.
* It should have stronger consistency guarantees than v2 auth
### Main required changes
* A client must create a dedicated connection only for authentication before sending authenticated requests
* Add permission information (user ID and authorized revision) to the Raft commands (`etcdserverpb.InternalRaftRequest`)
* Every request is permission checked in the state machine layer, rather than API layer
### Permission metadata consistency
The metadata for auth should also be stored and managed in the storage controlled by etcd's Raft protocol like other data stored in etcd. It is required for not sacrificing availability and consistency of the entire etcd cluster. If reading or writing the metadata (e.g. permission information) needs an agreement of every node (more than quorum), single node failure can stop the entire cluster. Requiring all nodes to agree at once means that checking ordinary read/write requests cannot be completed if any cluster member is down, even if the cluster has an available quorum. This unanimous scheme ultimately degrades cluster availability; quorum based consensus from raft should suffice since agreement follows from consistent ordering.
The authentication mechanism in the etcd v2 protocol has a tricky part because the metadata consistency should work as in the above, but does not: each permission check is processed by the etcd member that receives the client request (etcdserver/api/v2http/client.go), including follower members. Therefore, it's possible the check may be based on stale metadata.
This staleness means that auth configuration cannot be reflected as soon as operators execute etcdctl. Therefore there is no way to know how long the stale metadata is active. Practically, the configuration change is reflected immediately after the command execution. However, in some cases of heavy load, the inconsistent state can be prolonged and it might result in counter-intuitive situations for users and developers. It requires a workaround like this: https://github.com/coreos/etcd/pull/4317#issuecomment-179037582
### Inconsistent permissions are unsafe for linearized requests
Inconsistent authentication state is most serious for writes. Even if an operator disables write on a user, if the write is only ordered with respect to the key value store but not the authentication system, it's possible the write will complete successfully. Without ordering on both the auth store and the key-value store, the system will be susceptible to stale permission attacks.
Therefore, the permission checking logic should be added to the state machine of etcd. Each state machine should check the requests based on its permission information in the apply phase (so the auth information must not be stale).
## Design and implementation
### Authentication
At first, a client must create a gRPC connection only to authenticate its user ID and password. An etcd server will respond with an authentication reply. The reponse will be an authentication token on success or an error on failure. The client can use its authentication token to present its credentials to etcd when making API requests.
The client connection used to request the authentication token is typically thrown away; it cannot carry the new token's credentials. This is because gRPC doesn't provide a way for adding per RPC credential after creation of the connection (calling `grpc.Dial()`). Therefore, a client cannot assign a token to its connection that is obtained through the connection. The client needs a new connection for using the token.
#### Notes on the implementation of `Authenticate()` RPC
`Authenticate()` RPC generates an authentication token based on a given user name and password. etcd saves and checks a configured password and a given password using Go's `bcrypt` package. By design, `bcrypt`'s password checking mechanism is computationally expensive, taking nearly 100ms on an ordinary x64 server. Therefore, performing this check in the state machine apply phase would cause performance trouble: the entire etcd cluster can only serve almost 10 `Authenticate()` requests per second.
For good performance, the v3 auth mechanism checks passwords in etcd's API layer, where it can be parallelized outside of raft. However, this can lead to potential time-of-check/time-of-use (TOCTOU) permission lapses:
1. client A sends a request `Authenticate()`
1. the API layer processes the password checking part of `Authenticate()`
1. another client B sends a request of `ChangePassword()` and the server completes it
1. the state machine layer processes the part of getting a revision number for the `Authenticate()` from A
1. the server returns a success to A
1. now A is authenticated on an obsolete password
For avoiding such a situation, the API layer performs *version number validation* based on the revision number of the auth store. During password checking, the API layer saves the revision number of auth store. After successful password checking, the API layer compares the saved revision number and the latest revision number. If the numbers differ, it means someone else updated the auth metadata. So it retries the checking. With this mechanism, the successful password checking based on the obsolete password can be avoided.
### Resolving a token in the API layer
After authenticating with `Authenticate()`, a client can create a gRPC connection as it would without auth. In addition to the existing initialization process, the client must associate the token with the newly created connection. `grpc.WithPerRPCCredentials()` provides the functionality for this purpose.
Every authenticated request from the client has a token. The token can be obtained with `grpc.metadata.FromIncomingContext()` in the server side. The server can obtain who is issuing the request and when the user was authorized. The information will be filled by the API layer in the header (`etcdserverpb.RequestHeader.Username` and `etcdserverpb.RequestHeader.AuthRevision`) of a raft log entry (`etcdserverpb.InternalRaftRequest`).
### Checking permission in the state machine
The auth info in `etcdserverpb.RequestHeader` is checked in the apply phase of the state machine. This step checks the user is granted permission to requested keys on the latest revision of auth store.
### Two types of tokens: simple and JWT
There are two kinds of token types: simple and JWT. The simple token isn't designed for production use cases. Its tokens aren't cryptographically signed and servers must statefully track token-user correspondence; it is meant for development testing. JWT tokens should be used for production deployments since it is cryptographically signed and verified. From the implementation perspective, JWT is stateless. Its token can include metadata including username and revision, so servers don't need to remember correspondence between tokens and the metadata.
## Notes on the difference between KVS models and file system models
etcd v3 is a KVS, not a file system. So the permissions can be granted to the users in form of an exact key name or a key range like `["start key", "end key")`. It means that granting a permission of a nonexistent key is possible. Users should care about unintended permission granting. In a case of file system like system (e.g. Chubby or ZooKeeper), an inode like data structure can include the permission information. So granting permission to a nonexist key won't be possible (except the case of sticky bits).
The etcd v3 model requires multiple lookup of the metadata unlike the file system like systems. The worst case lookup cost will be sum the user's total granted keys and intervals. The cost cannot be avoided because v3's flat key space is completely different from Unix's file system model (every inode includes permission metadata). Practically the cost won’t be a serious problem because the metadata is small enough to benefit from caching.
etcd is designed to reliably store infrequently updated data and provide reliable watch queries. etcd exposes previous versions of key-value pairs to support inexpensive snapshots and watch history events (“time travel queries”). A persistent, multi-version, concurrency-control data model is a good fit for these use cases.
etcd stores data in a multiversion [persistent][persistent-ds] key-value store. The persistent key-value store preserves the previous version of a key-value pair when its value is superseded with new data. The key-value store is effectively immutable; its operations do not update the structure in-place, but instead always generate a new updated structure. All past versions of keys are still accessible and watchable after modification. To prevent the data store from growing indefinitely over time and from maintaining old versions, the store may be compacted to shed the oldest versions of superseded data.
### Logical view
The store’s logical view is a flat binary key space. The key space has a lexically sorted index on byte string keys so range queries are inexpensive.
The key space maintains multiple revisions. Each atomic mutative operation (e.g., a transaction operation may contain multiple operations) creates a new revision on the key space. All data held by previous revisions remains unchanged. Old versions of key can still be accessed through previous revisions. Likewise, revisions are indexed as well; ranging over revisions with watchers is efficient. If the store is compacted to save space, revisions before the compact revision will be removed.
A key’s lifetime spans a generation, denoted by its version. Each key may have one or multiple generations. Creating a key increments the version of that key, starting at 1 if the key never existed. Deleting a key generates a key tombstone, concluding the key’s current generation by resetting its version. Each modification of a key increments its version. Once a compaction happens, any version ended before the given revision will be removed and values set before the compaction revision except the latest one will be removed.
### Physical view
etcd stores the physical data as key-value pairs in a persistent [b+tree][b+tree]. Each revision of the store’s state only contains the delta from its previous revision to be efficient. A single revision may correspond to multiple keys in the tree.
The key of key-value pair is a 3-tuple (major, sub, type). Major is the store revision holding the key. Sub differentiates among keys within the same revision. Type is an optional suffix for special value (e.g., `t` if the value contains a tombstone). The value of the key-value pair contains the modification from previous revision, thus one delta from previous revision. The b+tree is ordered by key in lexical byte-order. Ranged lookups over revision deltas are fast; this enables quickly finding modifications from one specific revision to another. Compaction removes out-of-date keys-value pairs.
etcd also keeps a secondary in-memory [btree][btree] index to speed up range queries over keys. The keys in the btree index are the keys of the store exposed to user. The value is a pointer to the modification of the persistent b+tree. Compaction removes dead pointers.
This document defines the various terms used in etcd documentation, command line and source code.
## Alarm
The etcd server raises an alarm whenever the cluster needs operator intervention to remain reliable.
## Authentication
Authentication manages user access permissions for etcd resources.
## Client
A client connects to the etcd cluster to issue service requests such as fetching key-value pairs, writing data, or watching for updates.
## Cluster
Cluster consists of several members.
The node in each member follows raft consensus protocol to replicate logs. Cluster receives proposals from members, commits them and apply to local store.
## Compaction
Compaction discards all etcd event history and superseded keys prior to a given revision. It is used to reclaim storage space in the etcd backend database.
## Election
The etcd cluster holds elections among its members to choose a leader as part of the raft consensus protocol.
## Endpoint
A URL pointing to an etcd service or resource.
## Key
A user-defined identifier for storing and retrieving user-defined values in etcd.
## Key range
A set of keys containing either an individual key, a lexical interval for all x such that a <x<=b,orallkeysgreaterthanagivenkey.
The name "etcd" originated from two ideas, the unix "/etc" folder and "d"istibuted systems. The "/etc" folder is a place to store configuration data for a single system whereas etcd stores configuration information for large scale distributed systems. Hence, a "d"istributed "/etc" is "etcd".
etcd is designed as a general substrate for large scale distributed systems. These are systems that will never tolerate split-brain operation and are willing to sacrifice availability to achieve this end. etcd stores metadata in a consistent and fault-tolerant way. An etcd cluster is meant to provide key-value storage with best of class stability, reliability, scalability and performance.
Distributed systems use etcd as a consistent key-value store for configuration management, service discovery, and coordinating distributed work. Many [organizations][production-users] use etcd to implement production systems such as container schedulers, service discovery services, and distributed data storage. Common distributed patterns using etcd include [leader election][etcd-etcdctl-elect], [distributed locks][etcd-etcdctl-lock], and monitoring machine liveness.
## Use cases
- Container Linux by CoreOS: Applications running on [Container Linux][container-linux] get automatic, zero-downtime Linux kernel updates. Container Linux uses [locksmith] to coordinate updates. Locksmith implements a distributed semaphore over etcd to ensure only a subset of a cluster is rebooting at any given time.
- [Kubernetes][kubernetes] stores configuration data into etcd for service discovery and cluster management; etcd's consistency is crucial for correctly scheduling and operating services. The Kubernetes API server persists cluster state into etcd. It uses etcd's watch API to monitor the cluster and roll out critical configuration changes.
## Comparison chart
Perhaps etcd already seems like a good fit, but as with all technological decisions, proceed with caution. Please note this documentation is written by the etcd team. Although the ideal is a disinterested comparison of technology and features, the authors’ expertise and biases obviously favor etcd. Use only as directed.
The table below is a handy quick reference for spotting the differences among etcd and its most popular alternatives at a glance. Further commentary and details for each column are in the sections following the table.
| Concurrency Primitives | [Lock RPCs][etcd-v3lock], [Election RPCs][etcd-v3election], [command line locks][etcd-etcdctl-lock], [command line elections][etcd-etcdctl-elect], [recipes][etcd-recipe] in go | External [curator recipes][curator] in Java | [Native lock API][consul-lock] | [Rare][newsql-leader], if any |
| Linearizable Reads | [Yes][etcd-linread] | No | [Yes][consul-linread] | Sometimes |
| Multi-version Concurrency Control | [Yes][etcd-mvcc] | No | No | Sometimes |
ZooKeeper solves the same problem as etcd: distributed system coordination and metadata storage. However, etcd has the luxury of hindsight taken from engineering and operational experience with ZooKeeper’s design and implementation. The lessons learned from Zookeeper certainly informed etcd’s design, helping it support large scale systems like Kubernetes. The improvements etcd made over Zookeeper include:
* Dynamic cluster membership reconfiguration
* Stable read/write under high load
* A multi-version concurrency control data model
* Reliable key monitoring which never silently drop events
* Lease primitives decoupling connections from sessions
* APIs for safe distributed shared locks
Furthermore, etcd supports a wide range of languages and frameworks out of the box. Whereas Zookeeper has its own custom Jute RPC protocol, which is totally unique to Zookeeper and limits its [supported language bindings][zk-bindings], etcd’s client protocol is built from [gRPC][grpc], a popular RPC framework with language bindings for go, C++, Java, and more. Likewise, gRPC can be serialized into JSON over HTTP, so even general command line utilities like `curl` can talk to it. Since systems can select from a variety of choices, they are built on etcd with native tooling rather than around etcd with a single fixed set of technologies.
When considering features, support, and stability, new applications planning to use Zookeeper for a consistent key value store would do well to choose etcd instead.
### Consul
Consul bills itself as an end-to-end service discovery framework. To wit, it includes services such as health checking, failure detection, and DNS. Incidentally, Consul also exposes a key value store with mediocre performance and an intricate API. As it stands in Consul 0.7, the storage system does not scales well; systems requiring millions of keys will suffer from high latencies and memory pressure. The key value API is missing, most notably, multi-version keys, conditional transactions, and reliable streaming watches.
etcd and Consul solve different problems. If looking for a distributed consistent key value store, etcd is a better choice over Consul. If looking for end-to-end cluster service discovery, etcd will not have enough features; choose Kubernetes, Consul, or SmartStack.
### NewSQL (Cloud Spanner, CockroachDB, TiDB)
Both etcd and NewSQL databases (e.g., [Cockroach][cockroach], [TiDB][tidb], [Google Spanner][spanner]) provide strong data consistency guarantees with high availability. However, the significantly different system design parameters lead to significantly different client APIs and performance characteristics.
NewSQL databases are meant to horizontally scale across data centers. These systems typically partition data across multiple consistent replication groups (shards), potentially distant, storing data sets on the order of terabytes and above. This sort of scaling makes them poor candidates for distributed coordination as they have long latencies from waiting on clocks and expect updates with mostly localized dependency graphs. The data is organized into tables, including SQL-style query facilities with richer semantics than etcd, but at the cost of additional complexity for processing, planning, and optimizing queries.
In short, choose etcd for storing metadata or coordinating distributed applications. If storing more than a few GB of data or if full SQL queries are needed, choose a NewSQL database.
## Using etcd for metadata
etcd replicates all data within a single consistent replication group. For storing up to a few GB of data with consistent ordering, this is the most efficient approach. Each modification of cluster state, which may change multiple keys, is assigned a global unique ID, called a revision in etcd, from a monotonically increasing counter for reasoning over ordering. Since there’s only a single replication group, the modification request only needs to go through the raft protocol to commit. By limiting consensus to one replication group, etcd gets distributed consistency with a simple protocol while achieving low latency and high throughput.
The replication behind etcd cannot horizontally scale because it lacks data sharding. In contrast, NewSQL databases usually shard data across multiple consistent replication groups, storing data sets on the order of terabytes and above. However, to assign each modification a global unique and increasing ID, each request must go through an additional coordination protocol among replication groups. This extra coordination step may potentially conflict on the global ID, forcing ordered requests to retry. The result is a more complicated approach with typically worse performance than etcd for strict ordering.
If an application reasons primarily about metadata or metadata ordering, such as to coordinate processes, choose etcd. If the application needs a large data store spanning multiple data centers and does not heavily depend on strong global ordering properties, choose a NewSQL database.
## Using etcd for distributed coordination
etcd has distributed coordination primitives such as event watches, leases, elections, and distributed shared locks out of the box. These primitives are both maintained and supported by the etcd developers; leaving these primitives to external libraries shirks the responsibility of developing foundational distributed software, essentially leaving the system incomplete. NewSQL databases usually expect these distributed coordination primitives to be authored by third parties. Likewise, ZooKeeper famously has a separate and independent [library][curator] of coordination recipes. Consul, which provides a native locking API, goes so far as to apologize that it’s “[not a bulletproof method][consul-bulletproof]”.
In theory, it’s possible to build these primitives atop any storage systems providing strong consistency. However, the algorithms tend to be subtle; it is easy to develop a locking algorithm that appears to work, only to suddenly break due to thundering herd and timing skew. Furthermore, other primitives supported by etcd, such as transactional memory depend on etcd’s MVCC data model; simple strong consistency is not enough.
For distributed coordination, choosing etcd can help prevent operational headaches and save engineering effort.
etcd uses [Prometheus][prometheus] for metrics reporting. The metrics can be used for real-time monitoring and debugging. etcd does not persist its metrics; if a member restarts, the metrics will be reset.
The simplest way to see the available metrics is to cURL the metrics endpoint `/metrics`. The format is described [here](http://prometheus.io/docs/instrumenting/exposition_formats/).
Follow the [Prometheus getting started doc][prometheus-getting-started] to spin up a Prometheus server to collect etcd metrics.
The naming of metrics follows the suggested [Prometheus best practices][prometheus-naming]. A metric name has an `etcd` or `etcd_debugging` prefix as its namespace and a subsystem prefix (for example `wal` and `etcdserver`).
## etcd namespace metrics
The metrics under the `etcd` prefix are for monitoring and alerting. They are stable high level metrics. If there is any change of these metrics, it will be included in release notes.
Metrics that are etcd2 related are documented [v2 metrics guide][v2-http-metrics].
### Server
These metrics describe the status of the etcd server. In order to detect outages or problems for troubleshooting, the server metrics of every production etcd cluster should be closely monitored.
All these metrics are prefixed with `etcd_server_`
| has_leader | Whether or not a leader exists. 1 is existence, 0 is not.| Gauge |
| leader_changes_seen_total | The number of leader changes seen. | Counter |
| proposals_committed_total | The total number of consensus proposals committed. | Gauge |
| proposals_applied_total | The total number of consensus proposals applied. | Gauge |
| proposals_pending | The current number of pending proposals. | Gauge |
| proposals_failed_total | The total number of failed proposals seen. | Counter |
`has_leader` indicates whether the member has a leader. If a member does not have a leader, it is
totally unavailable. If all the members in the cluster do not have any leader, the entire cluster
is totally unavailable.
`leader_changes_seen_total` counts the number of leader changes the member has seen since its start. Rapid leadership changes impact the performance of etcd significantly. It also signals that the leader is unstable, perhaps due to network connectivity issues or excessive load hitting the etcd cluster.
`proposals_committed_total` records the total number of consensus proposals committed. This gauge should increase over time if the cluster is healthy. Several healthy members of an etcd cluster may have different total committed proposals at once. This discrepancy may be due to recovering from peers after starting, lagging behind the leader, or being the leader and therefore having the most commits. It is important to monitor this metric across all the members in the cluster; a consistently large lag between a single member and its leader indicates that member is slow or unhealthy.
`proposals_applied_total` records the total number of consensus proposals applied. The etcd server applies every committed proposal asynchronously. The difference between `proposals_committed_total` and `proposals_applied_total` should usually be small (within a few thousands even under high load). If the difference between them continues to rise, it indicates that the etcd server is overloaded. This might happen when applying expensive queries like heavy range queries or large txn operations.
`proposals_pending` indicates how many proposals are queued to commit. Rising pending proposals suggests there is a high client load or the member cannot commit proposals.
`proposals_failed_total` are normally related to two issues: temporary failures related to a leader election or longer downtime caused by a loss of quorum in the cluster.
### Disk
These metrics describe the status of the disk operations.
| wal_fsync_duration_seconds | The latency distributions of fsync called by wal | Histogram |
| backend_commit_duration_seconds | The latency distributions of commit called by backend.| Histogram |
A `wal_fsync` is called when etcd persists its log entries to disk before applying them.
A `backend_commit` is called when etcd commits an incremental snapshot of its most recent changes to disk.
High disk operation latencies (`wal_fsync_duration_seconds` or `backend_commit_duration_seconds`) often indicate disk issues. It may cause high request latency or make the cluster unstable.
### Network
These metrics describe the status of the network.
All these metrics are prefixed with `etcd_network_`
| peer_sent_bytes_total | The total number of bytes sent to the peer with ID `To`. | Counter(To) |
| peer_received_bytes_total | The total number of bytes received from the peer with ID `From`. | Counter(From) |
| peer_sent_failures_total | The total number of send failures from the peer with ID `To`. | Counter(To) |
| peer_received_failures_total | The total number of receive failures from the peer with ID `From`. | Counter(From) |
| peer_round_trip_time_seconds | Round-Trip-Time histogram between peers. | Histogram(To) |
| client_grpc_sent_bytes_total | The total number of bytes sent to grpc clients. | Counter |
| client_grpc_received_bytes_total| The total number of bytes received to grpc clients. | Counter |
`peer_sent_bytes_total` counts the total number of bytes sent to a specific peer. Usually the leader member sends more data than other members since it is responsible for transmitting replicated data.
`peer_received_bytes_total` counts the total number of bytes received from a specific peer. Usually follower members receive data only from the leader member.
### gRPC requests
These metrics are exposed via [go-grpc-prometheus][go-grpc-prometheus].
## etcd_debugging namespace metrics
The metrics under the `etcd_debugging` prefix are for debugging. They are very implementation dependent and volatile. They might be changed or removed without any warning in new etcd releases. Some of the metrics might be moved to the `etcd` prefix when they become more stable.
| process_open_fds | Number of open file descriptors. | Gauge |
| process_max_fds | Maximum number of open file descriptors. | Gauge |
Heavy file descriptor (`process_open_fds`) usage (i.e., near the process's file descriptor limit, `process_max_fds`) indicates a potential file descriptor exhaustion issue. If the file descriptors are exhausted, etcd may panic because it cannot create new WAL files.
Authentication was added in etcd 2.1. The etcd v3 API slightly modified the authentication feature's API and user interface to better fit the new data model. This guide is intended to help users set up basic authentication and role-based access control in etcd v3.
## Special users and roles
There is one special user, `root`, and one special role, `root`.
### User `root`
The `root` user, which has full access to etcd, must be created before activating authentication. The idea behind the `root` user is for administrative purposes: managing roles and ordinary users. The `root` user must have the `root` role and is allowed to change anything inside etcd.
### Role `root`
The role `root` may be granted to any user, in addition to the root user. A user with the `root` role has both global read-write access and permission to update the cluster's authentication configuration. Furthermore, the `root` role grants privileges for general cluster maintenance, including modifying cluster membership, defragmenting the store, and taking snapshots.
## Working with users
The `user` subcommand for `etcdctl` handles all things having to do with user accounts.
A listing of users can be found with:
```
$ etcdctl user list
```
Creating a user is as easy as
```
$ etcdctl user add myusername
```
Creating a new user will prompt for a new password. The password can be supplied from standard input when an option `--interactive=false` is given.
Roles can be granted and revoked for a user with:
```
$ etcdctl user grant-role myusername foo
$ etcdctl user revoke-role myusername bar
```
The user's settings can be inspected with:
```
$ etcdctl user get myusername
```
And the password for a user can be changed with
```
$ etcdctl user passwd myusername
```
Changing the password will prompt again for a new password. The password can be supplied from standard input when an option `--interactive=false` is given.
Delete an account with:
```
$ etcdctl user delete myusername
```
## Working with roles
The `role` subcommand for `etcdctl` handles all things having to do with access controls for particular roles, as were granted to individual users.
List roles with:
```
$ etcdctl role list
```
Create a new role with:
```
$ etcdctl role add myrolename
```
A role has no password; it merely defines a new set of access rights.
Roles are granted access to a single key or a range of keys.
The range can be specified as an interval [start-key, end-key) where start-key should be lexically less than end-key in an alphabetical manner.
Access can be granted as either read, write, or both, as in the following examples:
```
# Give read access to a key /foo
$ etcdctl role grant-permission myrolename read /foo
# Give read access to keys with a prefix /foo/. The prefix is equal to the range [/foo/, /foo0)
$ etcdctl role grant-permission myrolename --prefix=true read /foo/
# Give write-only access to the key at /foo/bar
$ etcdctl role grant-permission myrolename write /foo/bar
# Give full access to keys in a range of [key1, key5)
$ etcdctl role grant-permission myrolename readwrite key1 key5
# Give full access to keys with a prefix /pub/
$ etcdctl role grant-permission myrolename --prefix=true readwrite /pub/
```
To see what's granted, we can look at the role at any time:
```
$ etcdctl role get myrolename
```
Revocation of permissions is done the same logical way:
```
$ etcdctl role revoke-permission myrolename /foo/bar
```
As is removing a role entirely:
```
$ etcdctl role remove myrolename
```
## Enabling authentication
The minimal steps to enabling auth are as follows. The administrator can set up users and roles before or after enabling authentication, as a matter of preference.
Make sure the root user is created:
```
$ etcdctl user add root
Password of root:
```
Enable authentication:
```
$ etcdctl auth enable
```
After this, etcd is running with authentication enabled. To disable it for any reason, use the reciprocal command:
```
$ etcdctl --user root:rootpw auth disable
```
## Using `etcdctl` to authenticate
`etcdctl` supports a similar flag as `curl` for authentication.
```
$ etcdctl --user user:password get foo
```
The password can be taken from a prompt:
```
$ etcdctl --user user get foo
```
Otherwise, all `etcdctl` commands remain the same. Users and roles can still be created and modified, but require authentication by a user with the root role.
## Using TLS Common Name
If an etcd server is launched with the option `--client-cert-auth=true`, the field of Common Name (CN) in the client's TLS cert will be used as an etcd user. In this case, the common name authenticates the user and the client does not need a password. Note that if both of 1. `--client-cert-auth=true` is passed and CN is provided by the client, and 2. username and password are provided by the client, the username and password based authentication is prioritized.
Starting an etcd cluster statically requires that each member knows another in the cluster. In a number of cases, the IPs of the cluster members may be unknown ahead of time. In these cases, the etcd cluster can be bootstrapped with the help of a discovery service.
Once an etcd cluster is up and running, adding or removing members is done via [runtime reconfiguration][runtime-conf]. To better understand the design behind runtime reconfiguration, we suggest reading [the runtime configuration design document][runtime-reconf-design].
This guide will cover the following mechanisms for bootstrapping an etcd cluster:
* [Static](#static)
* [etcd Discovery](#etcd-discovery)
* [DNS Discovery](#dns-discovery)
Each of the bootstrapping mechanisms will be used to create a three machine etcd cluster with the following details:
|Name|Address|Hostname|
|------|---------|------------------|
|infra0|10.0.1.10|infra0.example.com|
|infra1|10.0.1.11|infra1.example.com|
|infra2|10.0.1.12|infra2.example.com|
## Static
As we know the cluster members, their addresses and the size of the cluster before starting, we can use an offline bootstrap configuration by setting the `initial-cluster` flag. Each machine will get either the following environment variables or command line:
Note that the URLs specified in `initial-cluster` are the _advertised peer URLs_, i.e. they should match the value of `initial-advertise-peer-urls` on the respective nodes.
If spinning up multiple clusters (or creating and destroying a single cluster) with same configuration for testing purpose, it is highly recommended that each cluster is given a unique `initial-cluster-token`. By doing this, etcd can generate unique cluster IDs and member IDs for the clusters even if they otherwise have the exact same configuration. This can protect etcd from cross-cluster-interaction, which might corrupt the clusters.
etcd listens on [`listen-client-urls`][conf-listen-client] to accept client traffic. etcd member advertises the URLs specified in [`advertise-client-urls`][conf-adv-client] to other members, proxies, clients. Please make sure the `advertise-client-urls` are reachable from intended clients. A common mistake is setting `advertise-client-urls` to localhost or leave it as default if the remote clients should reach etcd.
The command line parameters starting with `--initial-cluster` will be ignored on subsequent runs of etcd. Feel free to remove the environment variables or command line flags after the initial bootstrap process. If the configuration needs changes later (for example, adding or removing members to/from the cluster), see the [runtime configuration][runtime-conf] guide.
### TLS
etcd supports encrypted communication through the TLS protocol. TLS channels can be used for encrypted internal cluster communication between peers as well as encrypted client traffic. This section provides examples for setting up a cluster with peer and client TLS. Additional information detailing etcd's TLS support can be found in the [security guide][security-guide].
#### Self-signed certificates
A cluster using self-signed certificates both encrypts traffic and authenticates its connections. To start a cluster with self-signed certificates, each cluster member should have a unique key pair (`member.crt`, `member.key`) signed by a shared cluster CA certificate (`ca.crt`) for both peer connections and client connections. Certificates may be generated by following the etcd [TLS setup][tls-setup] example.
On each machine, etcd would be started with these flags:
If the cluster needs encrypted communication but does not require authenticated connections, etcd can be configured to automatically generate its keys. On initialization, each member creates its own set of keys based on its advertised IP addresses and hosts.
On each machine, etcd would be started with these flags:
In the following example, we have not included our new host in the list of enumerated nodes. If this is a new cluster, the node _must_ be added to the list of initial cluster members.
etcd: infra1 not listed in the initial cluster config
exit 1
```
In this example, we are attempting to map a node (infra0) on a different address (127.0.0.1:2380) than its enumerated address in the cluster list (10.0.1.10:2380). If this node is to listen on multiple addresses, all addresses _must_ be reflected in the "initial-cluster" configuration directive.
etcd: error setting up initial cluster: infra0 has different advertised URLs in the cluster and advertised peer URLs list
exit 1
```
If a peer is configured with a different set of configuration arguments and attempts to join this cluster, etcd will report a cluster ID mismatch will exit.
etcd: conflicting cluster ID to the target cluster (c6ab534d07e8fcc4 != bc25ea2a74fb18b0). Exiting.
exit 1
```
## Discovery
In a number of cases, the IPs of the cluster peers may not be known ahead of time. This is common when utilizing cloud providers or when the network uses DHCP. In these cases, rather than specifying a static configuration, use an existing etcd cluster to bootstrap a new one. This process is called "discovery".
There two methods that can be used for discovery:
* etcd discovery service
* DNS SRV records
### etcd discovery
To better understand the design of the discovery service protocol, we suggest reading the discovery service protocol [documentation][discovery-proto].
#### Lifetime of a discovery URL
A discovery URL identifies a unique etcd cluster. Instead of reusing an existing discovery URL, each etcd instance shares a new discovery URL to bootstrap the new cluster.
Moreover, discovery URLs should ONLY be used for the initial bootstrapping of a cluster. To change cluster membership after the cluster is already running, see the [runtime reconfiguration][runtime-conf] guide.
#### Custom etcd discovery service
Discovery uses an existing cluster to bootstrap itself. If using a private etcd cluster, create a URL like so:
```
$ curl -X PUT https://myetcd.local/v2/keys/discovery/6c007a14875d53d9bf0ef5a6fc0257c817f0fb83/_config/size -d value=3
```
By setting the size key to the URL, a discovery URL is created with an expected cluster size of 3.
The URL to use in this case will be `https://myetcd.local/v2/keys/discovery/6c007a14875d53d9bf0ef5a6fc0257c817f0fb83` and the etcd members will use the `https://myetcd.local/v2/keys/discovery/6c007a14875d53d9bf0ef5a6fc0257c817f0fb83` directory for registration as they start.
**Each member must have a different name flag specified. `Hostname` or `machine-id` can be a good choice. Or discovery will fail due to duplicated name.**
Now we start etcd with those relevant flags for each member:
This will cause each member to register itself with the custom etcd discovery service and begin the cluster once all machines have been registered.
#### Public etcd discovery service
If no exiting cluster is available, use the public discovery service hosted at `discovery.etcd.io`. To create a private discovery URL using the "new" endpoint, use the command:
**Each member must have a different name flag specified or else discovery will fail due to duplicated names. `Hostname` or `machine-id` can be a good choice.**
Now we start etcd with those relevant flags for each member:
etcdserver: discovery token ignored since a cluster has already been initialized. Valid log found at /var/lib/etcd
```
### DNS discovery
DNS [SRV records][rfc-srv] can be used as a discovery mechanism.
The `-discovery-srv` flag can be used to set the DNS domain name where the discovery SRV records can be found.
The following DNS SRV records are looked up in the listed order:
* _etcd-server-ssl._tcp.example.com
* _etcd-server._tcp.example.com
If `_etcd-server-ssl._tcp.example.com` is found then etcd will attempt the bootstrapping process over TLS.
To help clients discover the etcd cluster, the following DNS SRV records are looked up in the listed order:
* _etcd-client._tcp.example.com
* _etcd-client-ssl._tcp.example.com
If `_etcd-client-ssl._tcp.example.com` is found, clients will attempt to communicate with the etcd cluster over SSL/TLS.
If etcd is using TLS without a custom certificate authority, the discovery domain (e.g., example.com) must match the SRV record domain (e.g., infra1.example.com). This is to mitigate attacks that forge SRV records to point to a different domain; the domain would have a valid certificate under PKI but be controlled by an unknown third party.
etcd cluster members can listen on domain names or IP address, the bootstrap process will resolve DNS A records.
The resolved address in `--initial-advertise-peer-urls`*must match* one of the resolved addresses in the SRV targets. The etcd member reads the resolved address to find out if it belongs to the cluster defined in the SRV records.
Since v3.1.0 (except v3.2.9), when `etcd --discovery-srv=example.com` is configured with TLS, server will only authenticate peers/clients when the provided certs have root domain `example.com` as an entry in Subject Alternative Name (SAN) field. See [Notes for DNS SRV][security-guide-dns-srv].
### Gateway
etcd gateway is a simple TCP proxy that forwards network data to the etcd cluster. Please read [gateway guide][gateway] for more information.
### Proxy
When the `--proxy` flag is set, etcd runs in [proxy mode][proxy]. This proxy mode only supports the etcd v2 API; there are no plans to support the v3 API. Instead, for v3 API support, there will be a new proxy with enhanced features following the etcd 3.0 release.
To setup an etcd cluster with proxies of v2 API, please read the the [clustering doc in etcd 2.3 release][clustering_etcd2].
etcd is configurable through command-line flags and environment variables. Options set on the command line take precedence over those from the environment.
The format of environment variable for flag `--my-flag` is `ETCD_MY_FLAG`. It applies to all flags.
The [official etcd ports][iana-ports] are 2379 for client requests and 2380 for peer communication. The etcd ports can be set to accept TLS traffic, non-TLS traffic, or both TLS and non-TLS traffic.
To start etcd automatically using custom settings at startup in Linux, using a [systemd][systemd-intro] unit is highly recommended.
## Member flags
### --name
+ Human-readable name for this member.
+ default: "default"
+ env variable: ETCD_NAME
+ This value is referenced as this node's own entries listed in the `--initial-cluster` flag (e.g., `default=http://localhost:2380`). This needs to match the key used in the flag if using [static bootstrapping][build-cluster]. When using discovery, each member must have a unique name. `Hostname` or `machine-id` can be a good choice.
### --data-dir
+ Path to the data directory.
+ default: "${name}.etcd"
+ env variable: ETCD_DATA_DIR
### --wal-dir
+ Path to the dedicated wal directory. If this flag is set, etcd will write the WAL files to the walDir rather than the dataDir. This allows a dedicated disk to be used, and helps avoid io competition between logging and other IO operations.
+ default: ""
+ env variable: ETCD_WAL_DIR
### --snapshot-count
+ Number of committed transactions to trigger a snapshot to disk.
+ default: "100000"
+ env variable: ETCD_SNAPSHOT_COUNT
### --heartbeat-interval
+ Time (in milliseconds) of a heartbeat interval.
+ default: "100"
+ env variable: ETCD_HEARTBEAT_INTERVAL
### --election-timeout
+ Time (in milliseconds) for an election to timeout. See [Documentation/tuning.md][tuning] for details.
+ default: "1000"
+ env variable: ETCD_ELECTION_TIMEOUT
### --listen-peer-urls
+ List of URLs to listen on for peer traffic. This flag tells the etcd to accept incoming requests from its peers on the specified scheme://IP:port combinations. Scheme can be either http or https.If 0.0.0.0 is specified as the IP, etcd listens to the given port on all interfaces. If an IP address is given as well as a port, etcd will listen on the given port and interface. Multiple URLs may be used to specify a number of addresses and ports to listen on. The etcd will respond to requests from any of the listed addresses and ports.
+ default: "http://localhost:2380"
+ env variable: ETCD_LISTEN_PEER_URLS
+ example: "http://10.0.0.1:2380"
+ invalid example: "http://example.com:2380" (domain name is invalid for binding)
### --listen-client-urls
+ List of URLs to listen on for client traffic. This flag tells the etcd to accept incoming requests from the clients on the specified scheme://IP:port combinations. Scheme can be either http or https. If 0.0.0.0 is specified as the IP, etcd listens to the given port on all interfaces. If an IP address is given as well as a port, etcd will listen on the given port and interface. Multiple URLs may be used to specify a number of addresses and ports to listen on. The etcd will respond to requests from any of the listed addresses and ports.
+ default: "http://localhost:2379"
+ env variable: ETCD_LISTEN_CLIENT_URLS
+ example: "http://10.0.0.1:2379"
+ invalid example: "http://example.com:2379" (domain name is invalid for binding)
### --max-snapshots
+ Maximum number of snapshot files to retain (0 is unlimited)
+ default: 5
+ env variable: ETCD_MAX_SNAPSHOTS
+ The default for users on Windows is unlimited, and manual purging down to 5 (or some preference for safety) is recommended.
### --max-wals
+ Maximum number of wal files to retain (0 is unlimited)
+ default: 5
+ env variable: ETCD_MAX_WALS
+ The default for users on Windows is unlimited, and manual purging down to 5 (or some preference for safety) is recommended.
### --cors
+ Comma-separated white list of origins for CORS (cross-origin resource sharing).
+ default: ""
+ env variable: ETCD_CORS
### --quota-backend-bytes
+ Raise alarms when backend size exceeds the given quota (0 defaults to low space quota).
+ default: 0
+ env variable: ETCD_QUOTA_BACKEND_BYTES
### --max-txn-ops
+ Maximum number of operations permitted in a transaction.
+ default: 128
+ env variable: ETCD_MAX_TXN_OPS
### --max-request-bytes
+ Maximum client request size in bytes the server will accept.
+ default: 1572864
+ env variable: ETCD_MAX_REQUEST_BYTES
### --grpc-keepalive-min-time
+ Minimum duration interval that a client should wait before pinging server.
+ default: 5s
+ env variable: ETCD_GRPC_KEEPALIVE_MIN_TIME
### --grpc-keepalive-interval
+ Frequency duration of server-to-client ping to check if a connection is alive (0 to disable).
+ default: 2h
+ env variable: ETCD_GRPC_KEEPALIVE_INTERVAL
### --grpc-keepalive-timeout
+ Additional duration of wait before closing a non-responsive connection (0 to disable).
+ default: 20s
+ env variable: ETCD_GRPC_KEEPALIVE_TIMEOUT
## Clustering flags
`--initial` prefix flags are used in bootstrapping ([static bootstrap][build-cluster], [discovery-service bootstrap][discovery] or [runtime reconfiguration][reconfig]) a new member, and ignored when restarting an existing member.
`--discovery` prefix flags need to be set when using [discovery service][discovery].
### --initial-advertise-peer-urls
+ List of this member's peer URLs to advertise to the rest of the cluster. These addresses are used for communicating etcd data around the cluster. At least one must be routable to all cluster members. These URLs can contain domain names.
+ Initial cluster configuration for bootstrapping.
+ default: "default=http://localhost:2380"
+ env variable: ETCD_INITIAL_CLUSTER
+ The key is the value of the `--name` flag for each node provided. The default uses `default` for the key because this is the default for the `--name` flag.
### --initial-cluster-state
+ Initial cluster state ("new" or "existing"). Set to `new` for all members present during initial static or DNS bootstrapping. If this option is set to `existing`, etcd will attempt to join the existing cluster. If the wrong value is set, etcd will attempt to start but fail safely.
+ default: "new"
+ env variable: ETCD_INITIAL_CLUSTER_STATE
[static bootstrap]: clustering.md#static
### --initial-cluster-token
+ Initial cluster token for the etcd cluster during bootstrap.
+ default: "etcd-cluster"
+ env variable: ETCD_INITIAL_CLUSTER_TOKEN
### --advertise-client-urls
+ List of this member's client URLs to advertise to the rest of the cluster. These URLs can contain domain names.
+ Be careful if advertising URLs such as http://localhost:2379 from a cluster member and are using the proxy feature of etcd. This will cause loops, because the proxy will be forwarding requests to itself until its resources (memory, file descriptors) are eventually depleted.
### --discovery
+ Discovery URL used to bootstrap the cluster.
+ default: ""
+ env variable: ETCD_DISCOVERY
### --discovery-srv
+ DNS srv domain used to bootstrap the cluster.
+ default: ""
+ env variable: ETCD_DISCOVERY_SRV
### --discovery-fallback
+ Expected behavior ("exit" or "proxy") when discovery services fails. "proxy" supports v2 API only.
+ default: "proxy"
+ env variable: ETCD_DISCOVERY_FALLBACK
### --discovery-proxy
+ HTTP proxy to use for traffic to discovery service.
+ default: ""
+ env variable: ETCD_DISCOVERY_PROXY
### --strict-reconfig-check
+ Reject reconfiguration requests that would cause quorum loss.
+ default: false
+ env variable: ETCD_STRICT_RECONFIG_CHECK
### --auto-compaction-retention
+ Auto compaction retention for mvcc key value store in hour. 0 means disable auto compaction.
+ default: 0
+ env variable: ETCD_AUTO_COMPACTION_RETENTION
### --auto-compaction-mode
+ Interpret 'auto-compaction-retention' one of: periodic|revision. 'periodic' for duration based retention, defaulting to hours if no time unit is provided (e.g. '5m'). 'revision' for revision number based retention.
+ default: periodic
+ env variable: ETCD_AUTO_COMPACTION_MODE
### --enable-v2
+ Accept etcd V2 client requests
+ default: true
+ env variable: ETCD_ENABLE_V2
## Proxy flags
`--proxy` prefix flags configures etcd to run in [proxy mode][proxy]. "proxy" supports v2 API only.
### --proxy
+ Proxy mode setting ("off", "readonly" or "on").
+ default: "off"
+ env variable: ETCD_PROXY
### --proxy-failure-wait
+ Time (in milliseconds) an endpoint will be held in a failed state before being reconsidered for proxied requests.
+ default: 5000
+ env variable: ETCD_PROXY_FAILURE_WAIT
### --proxy-refresh-interval
+ Time (in milliseconds) of the endpoints refresh interval.
+ default: 30000
+ env variable: ETCD_PROXY_REFRESH_INTERVAL
### --proxy-dial-timeout
+ Time (in milliseconds) for a dial to timeout or 0 to disable the timeout
+ default: 1000
+ env variable: ETCD_PROXY_DIAL_TIMEOUT
### --proxy-write-timeout
+ Time (in milliseconds) for a write to timeout or 0 to disable the timeout.
+ default: 5000
+ env variable: ETCD_PROXY_WRITE_TIMEOUT
### --proxy-read-timeout
+ Time (in milliseconds) for a read to timeout or 0 to disable the timeout.
+ Don't change this value if using watches because use long polling requests.
+ default: 0
+ env variable: ETCD_PROXY_READ_TIMEOUT
## Security flags
The security flags help to [build a secure etcd cluster][security].
### --ca-file
**DEPRECATED**
+ Path to the client server TLS CA file. `--ca-file ca.crt` could be replaced by `--trusted-ca-file ca.crt --client-cert-auth` and etcd will perform the same.
+ default: ""
+ env variable: ETCD_CA_FILE
### --cert-file
+ Path to the client server TLS cert file.
+ default: ""
+ env variable: ETCD_CERT_FILE
### --key-file
+ Path to the client server TLS key file.
+ default: ""
+ env variable: ETCD_KEY_FILE
### --client-cert-auth
+ Enable client cert authentication.
+ default: false
+ env variable: ETCD_CLIENT_CERT_AUTH
### --client-crl-file
+ Path to the client certificate revocation list file.
+ default: ""
+ env variable: ETCD_CLIENT_CRL_FILE
### --trusted-ca-file
+ Path to the client server TLS trusted CA cert file.
+ default: ""
+ env variable: ETCD_TRUSTED_CA_FILE
### --auto-tls
+ Client TLS using generated certificates
+ default: false
+ env variable: ETCD_AUTO_TLS
### --peer-ca-file
**DEPRECATED**
+ Path to the peer server TLS CA file. `--peer-ca-file ca.crt` could be replaced by `--peer-trusted-ca-file ca.crt --peer-client-cert-auth` and etcd will perform the same.
+ default: ""
+ env variable: ETCD_PEER_CA_FILE
### --peer-cert-file
+ Path to the peer server TLS cert file.
+ default: ""
+ env variable: ETCD_PEER_CERT_FILE
### --peer-key-file
+ Path to the peer server TLS key file.
+ default: ""
+ env variable: ETCD_PEER_KEY_FILE
### --peer-client-cert-auth
+ Enable peer client cert authentication.
+ default: false
+ env variable: ETCD_PEER_CLIENT_CERT_AUTH
### --peer-crl-file
+ Path to the peer certificate revocation list file.
+ default: ""
+ env variable: ETCD_PEER_CRL_FILE
### --peer-trusted-ca-file
+ Path to the peer server TLS trusted CA file.
+ default: ""
+ env variable: ETCD_PEER_TRUSTED_CA_FILE
### --peer-auto-tls
+ Peer TLS using generated certificates
+ default: false
+ env variable: ETCD_PEER_AUTO_TLS
### --peer-cert-allowed-cn
+ Allowed CommonName for inter peer authentication.
+ default: none
+ env variable: ETCD_PEER_CERT_ALLOWED_CN
## Logging flags
### --debug
+ Drop the default log level to DEBUG for all subpackages.
+ default: false (INFO for all packages)
+ env variable: ETCD_DEBUG
### --log-package-levels
+ Set individual etcd subpackages to specific log levels. An example being `etcdserver=WARNING,security=DEBUG`
+ default: "" (INFO for all packages)
+ env variable: ETCD_LOG_PACKAGE_LEVELS
## Unsafe flags
Please be CAUTIOUS when using unsafe flags because it will break the guarantees given by the consensus protocol.
For example, it may panic if other members in the cluster are still alive.
Follow the instructions when using these flags.
### --force-new-cluster
+ Force to create a new one-member cluster. It commits configuration changes forcing to remove all existing members in the cluster and add itself. It needs to be set to [restore a backup][restore].
+ default: false
+ env variable: ETCD_FORCE_NEW_CLUSTER
## Miscellaneous flags
### --version
+ Print the version and exit.
+ default: false
### --config-file
+ Load server configuration from a file.
+ default: ""
## Profiling flags
### --enable-pprof
+ Enable runtime profiling data via HTTP server. Address is at client URL + "/debug/pprof/"
+ default: false
### --metrics
+ Set level of detail for exported metrics, specify 'extensive' to include histogram metrics.
+ default: basic
### --listen-metrics-urls
+ List of URLs to listen on for metrics.
+ default: ""
## Auth flags
### --auth-token
+ Specify a token type and token specific options, especially for JWT. Its format is "type,var1=val1,var2=val2,...". Possible type is 'simple' or 'jwt'. Possible variables are 'sign-method' for specifying a sign method of jwt (its possible values are 'ES256', 'ES384', 'ES512', 'HS256', 'HS384', 'HS512', 'RS256', 'RS384', 'RS512', 'PS256', 'PS384', or 'PS512'), 'pub-key' for specifying a path to a public key for verifying jwt, and 'priv-key' for specifying a path to a private key for signing jwt.
+ Example option of JWT: '--auth-token jwt,pub-key=app.rsa.pub,priv-key=app.rsa,sign-method=RS512'
+ default: "simple"
## Experimental flags
### --experimental-corrupt-check-time
+ Duration of time between cluster corruption check passes
ETCDCTL_API=3 etcdctl --endpoints=http://172.16.28.21:2379,http://172.16.28.22:2379,http://172.16.28.23:2379 endpoint health
```
### DNS
Production clusters which refer to peers by DNS name known to the local resolver must mount the [host's DNS configuration](https://coreos.com/kubernetes/docs/latest/kubelet-wrapper.html#customizing-rkt-options).
## Docker
In order to expose the etcd API to clients outside of Docker host, use the host IP address of the container. Please see [`docker inspect`](https://docs.docker.com/engine/reference/commandline/inspect) for more detail on how to get the IP address. Alternatively, specify `--net=host` flag to `docker run` command to skip placing the container inside of a separate network stack.
To provision a 3 node etcd cluster on bare-metal, the examples in the [baremetal repo](https://github.com/coreos/coreos-baremetal/tree/master/examples) may be useful.
## Mounting a certificate volume
The etcd release container does not include default root certificates. To use HTTPS with certificates trusted by a root authority (e.g., for discovery), mount a certificate directory into the etcd container:
# alert if another failed member will result in an unavailable cluster
ALERT InsufficientMembers
IF count(up{job="etcd"} == 0) > (count(up{job="etcd"}) / 2 - 1)
FOR 3m
LABELS {
severity = "critical"
}
ANNOTATIONS {
summary = "etcd cluster insufficient members",
description = "If one more etcd member goes down the cluster will be unavailable",
}
# etcd leader alerts
# ==================
# alert if any etcd instance has no leader
ALERT NoLeader
IF etcd_server_has_leader{job="etcd"} == 0
FOR 1m
LABELS {
severity = "critical"
}
ANNOTATIONS {
summary = "etcd member has no leader",
description = "etcd member {{ $labels.instance }} has no leader",
}
# alert if there are lots of leader changes
ALERT HighNumberOfLeaderChanges
IF increase(etcd_server_leader_changes_seen_total{job="etcd"}[1h]) > 3
LABELS {
severity = "warning"
}
ANNOTATIONS {
summary = "a high number of leader changes within the etcd cluster are happening",
description = "etcd instance {{ $labels.instance }} has seen {{ $value }} leader changes within the last hour",
}
# gRPC request alerts
# ===================
# alert if more than 1% of gRPC method calls have failed within the last 5 minutes
ALERT HighNumberOfFailedGRPCRequests
IF sum by(grpc_method) (rate(etcd_grpc_requests_failed_total{job="etcd"}[5m]))
/ sum by(grpc_method) (rate(etcd_grpc_total{job="etcd"}[5m])) > 0.01
FOR 10m
LABELS {
severity = "warning"
}
ANNOTATIONS {
summary = "a high number of gRPC requests are failing",
description = "{{ $value }}% of requests for {{ $labels.grpc_method }} failed on etcd instance {{ $labels.instance }}",
}
# alert if more than 5% of gRPC method calls have failed within the last 5 minutes
ALERT HighNumberOfFailedGRPCRequests
IF sum by(grpc_method) (rate(etcd_grpc_requests_failed_total{job="etcd"}[5m]))
/ sum by(grpc_method) (rate(etcd_grpc_total{job="etcd"}[5m])) > 0.05
FOR 5m
LABELS {
severity = "critical"
}
ANNOTATIONS {
summary = "a high number of gRPC requests are failing",
description = "{{ $value }}% of requests for {{ $labels.grpc_method }} failed on etcd instance {{ $labels.instance }}",
}
# alert if the 99th percentile of gRPC method calls take more than 150ms
ALERT GRPCRequestsSlow
IF histogram_quantile(0.99, sum(rate(grpc_server_handling_seconds_bucket{job="etcd",grpc_type="unary"}[5m])) by (grpc_service, grpc_method, le)) > 0.15
FOR 10m
LABELS {
severity = "critical"
}
ANNOTATIONS {
summary = "slow gRPC requests",
description = "on etcd instance {{ $labels.instance }} gRPC requests to {{ $labels.grpc_method }} are slow",
}
# HTTP requests alerts
# ====================
# alert if more than 1% of requests to an HTTP endpoint have failed within the last 5 minutes
ALERT HighNumberOfFailedHTTPRequests
IF sum(rate(grpc_server_handled_total{grpc_code!="OK",job="etcd"}[5m])) BY (grpc_service, grpc_method)
/ sum(rate(grpc_server_handled_total{job="etcd"}[5m])) BY (grpc_service, grpc_method) > 0.01
FOR 10m
LABELS {
severity = "warning"
}
ANNOTATIONS {
summary = "a high number of HTTP requests are failing",
description = "{{ $value }}% of requests for {{ $labels.method }} failed on etcd instance {{ $labels.instance }}",
}
# alert if more than 5% of requests to an HTTP endpoint have failed within the last 5 minutes
ALERT HighNumberOfFailedHTTPRequests
IF sum(rate(grpc_server_handled_total{grpc_code!="OK",job="etcd"}[5m])) BY (grpc_service, grpc_method)
/ sum(rate(grpc_server_handled_total{job="etcd"}[5m])) BY (grpc_service, grpc_method) > 0.05
FOR 5m
LABELS {
severity = "critical"
}
ANNOTATIONS {
summary = "a high number of HTTP requests are failing",
description = "{{ $value }}% of requests for {{ $labels.method }} failed on etcd instance {{ $labels.instance }}",
}
# alert if the 99th percentile of HTTP requests take more than 150ms
ALERT HTTPRequestsSlow
IF histogram_quantile(0.99, rate(etcd_http_successful_duration_seconds_bucket[5m])) > 0.15
FOR 10m
LABELS {
severity = "warning"
}
ANNOTATIONS {
summary = "slow HTTP requests",
description = "on etcd instance {{ $labels.instance }} HTTP requests to {{ $labels.method }} are slow",
Failures are common in a large deployment of machines. A machine fails when its hardware or software malfunctions. Multiple machines fail together when there are power failures or network issues. Multiple kinds of failures can also happen at once; it is almost impossible to enumerate all possible failure cases.
In this section, we catalog kinds of failures and discuss how etcd is designed to tolerate these failures. Most users, if not all, can map a particular failure into one kind of failure. To prepare for rare or [unrecoverable failures][unrecoverable], always [back up][backup] the etcd cluster.
## Minor followers failure
When fewer than half of the followers fail, the etcd cluster can still accept requests and make progress without any major disruption. For example, two follower failures will not affect a five member etcd cluster’s operation. However, clients will lose connectivity to the failed members. Client libraries should hide these interruptions from users for read requests by automatically reconnecting to other members. Operators should expect the system load on the other members to increase due to the reconnections.
## Leader failure
When a leader fails, the etcd cluster automatically elects a new leader. The election does not happen instantly once the leader fails. It takes about an election timeout to elect a new leader since the failure detection model is timeout based.
During the leader election the cluster cannot process any writes. Write requests sent during the election are queued for processing until a new leader is elected.
Writes already sent to the old leader but not yet committed may be lost. The new leader has the power to rewrite any uncommitted entries from the previous leader. From the user perspective, some write requests might time out after a new leader election. However, no committed writes are ever lost.
The new leader extends timeouts automatically for all leases. This mechanism ensures a lease will not expire before the granted TTL even if it was granted by the old leader.
## Majority failure
When the majority members of the cluster fail, the etcd cluster fails and cannot accept more writes.
The etcd cluster can only recover from a majority failure once the majority of members become available. If a majority of members cannot come back online, then the operator must start [disaster recovery][unrecoverable] to recover the cluster.
Once a majority of members works, the etcd cluster elects a new leader automatically and returns to a healthy state. The new leader extends timeouts automatically for all leases. This mechanism ensures no lease expires due to server side unavailability.
## Network partition
A network partition is similar to a minor followers failure or a leader failure. A network partition divides the etcd cluster into two parts; one with a member majority and the other with a member minority. The majority side becomes the available cluster and the minority side is unavailable; there is no “split-brain” in etcd.
If the leader is on the majority side, then from the majority point of view the failure is a minority follower failure. If the leader is on the minority side, then it is a leader failure. The leader on the minority side steps down and the majority side elects a new leader.
Once the network partition clears, the minority side automatically recognizes the leader from the majority side and recovers its state.
## Failure during bootstrapping
A cluster bootstrap is only successful if all required members successfully start. If any failure happens during bootstrapping, remove the data directories on all members and re-bootstrap the cluster with a new cluster-token or new discovery token.
Of course, it is possible to recover a failed bootstrapped cluster like recovering a running cluster. However, it almost always takes more time and resources to recover that cluster than bootstrapping a new one, since there is no data to recover.
etcd gateway is a simple TCP proxy that forwards network data to the etcd cluster. The gateway is stateless and transparent; it neither inspects client requests nor interferes with cluster responses.
The gateway supports multiple etcd server endpoints and works on a simple round-robin policy. It only routes to available enpoints and hides failures from its clients. Other retry policies, such as weighted round-robin, may be supported in the future.
## When to use etcd gateway
Every application that accesses etcd must first have the address of an etcd cluster client endpoint. If multiple applications on the same server access the same etcd cluster, every application still needs to know the advertised client endpoints of the etcd cluster. If the etcd cluster is reconfigured to have different endpoints, every application may also need to update its endpoint list. This wide-scale reconfiguration is both tedious and error prone.
etcd gateway solves this problem by serving as a stable local endpoint. A typical etcd gateway configuration has each machine running a gateway listening on a local address and every etcd application connecting to its local gateway. The upshot is only the gateway needs to update its endpoints instead of updating each and every application.
In summary, to automatically propagate cluster endpoint changes, the etcd gateway runs on every machine serving multiple applications accessing the same etcd cluster.
## When not to use etcd gateway
- Improving performance
The gateway is not designed for improving etcd cluster performance. It does not provide caching, watch coalescing or batching. The etcd team is developing a caching proxy designed for improving cluster scalability.
- Running on a cluster management system
Advanced cluster management systems like Kubernetes natively support service discovery. Applications can access an etcd cluster with a DNS name or a virtual IP address managed by the system. For example, kube-proxy is equivalent to etcd gateway.
## Start etcd gateway
Consider an etcd cluster with the following static endpoints:
|Name|Address|Hostname|
|------|---------|------------------|
|infra0|10.0.1.10|infra0.example.com|
|infra1|10.0.1.11|infra1.example.com|
|infra2|10.0.1.12|infra2.example.com|
Start the etcd gateway to use these static endpoints with the command:
The gRPC proxy is a stateless etcd reverse proxy operating at the gRPC layer (L7). The proxy is designed to reduce the total processing load on the core etcd cluster. For horizontal scalability, it coalesces watch and lease API requests. To protect the cluster against abusive clients, it caches key range requests.
The gRPC proxy supports multiple etcd server endpoints. When the proxy starts, it randomly picks one etcd server endpoint to use. This endpoint serves all requests until the proxy detects an endpoint failure. If the gRPC proxy detects an endpoint failure, it switches to a different endpoint, if available, to hide failures from its clients. Other retry policies, such as weighted round-robin, may be supported in the future.
## Scalable watch API
The gRPC proxy coalesces multiple client watchers (`c-watchers`) on the same key or range into a single watcher (`s-watcher`) connected to an etcd server. The proxy broadcasts all events from the `s-watcher` to its `c-watchers`.
Assuming N clients watch the same key, one gRPC proxy can reduce the watch load on the etcd server from N to 1. Users can deploy multiple gRPC proxies to further distribute server load.
In the following example, three clients watch on key A. The gRPC proxy coalesces the three watchers, creating a single watcher attached to the etcd server.
```
+-------------+
| etcd server |
+------+------+
^ watch key A (s-watcher)
|
+-------+-----+
| gRPC proxy | <-------+
| | |
++-----+------+ |watch key A (c-watcher)
watch key A ^ ^ watch key A |
(c-watcher) | | (c-watcher) |
+-------+-+ ++--------+ +----+----+
| client | | client | | client |
| | | | | |
+---------+ +---------+ +---------+
```
### Limitations
To effectively coalesce multiple client watchers into a single watcher, the gRPC proxy coalesces new `c-watchers` into an existing `s-watcher` when possible. This coalesced `s-watcher` may be out of sync with the etcd server due to network delays or buffered undelivered events. When the watch revision is unspecified, the gRPC proxy will not guarantee the `c-watcher` will start watching from the most recent store revision. For example, if a client watches from an etcd server with revision 1000, that watcher will begin at revision 1000. If a client watches from the gRPC proxy, may begin watching from revision 990.
Similar limitations apply to cancellation. When the watcher is cancelled, the etcd server’s revision may be greater than the cancellation response revision.
These two limitations should not cause problems for most use cases. In the future, there may be additional options to force the watcher to bypass the gRPC proxy for more accurate revision responses.
## Scalable lease API
To keep its leases alive, a client must establish at least one gRPC stream to an etcd server for sending periodic heartbeats. If an etcd workload involves heavy lease activity spread over many clients, these streams may contribute to excessive CPU utilization. To reduce the total number of streams on the core cluster, the proxy supports lease stream coalescing.
Assuming N clients are updating leases, a single gRPC proxy reduces the stream load on the etcd server from N to 1. Deployments may have additional gRPC proxies to further distribute streams across multiple proxies.
In the following example, three clients update three independent leases (`L1`, `L2`, and `L3`). The gRPC proxy coalesces the three client lease streams (`c-streams`) into a single lease keep alive stream (`s-stream`) attached to an etcd server. The proxy forwards client-side lease heartbeats from the c-streams to the s-stream, then returns the responses to the corresponding c-streams.
```
+-------------+
| etcd server |
+------+------+
^
| heartbeat L1, L2, L3
| (s-stream)
v
+-------+-----+
| gRPC proxy +<-----------+
+---+------+--+ | heartbeat L3
^ ^ | (c-stream)
heartbeat L1 | | heartbeat L2 |
(c-stream) v v (c-stream) v
+------+-+ +-+------+ +-----+--+
| client | | client | | client |
+--------+ +--------+ +--------+
```
## Abusive clients protection
The gRPC proxy caches responses for requests when it does not break consistency requirements. This can protect the etcd server from abusive clients in tight for loops.
## Start etcd gRPC proxy
Consider an etcd cluster with the following static endpoints:
|Name|Address|Hostname|
|------|---------|------------------|
|infra0|10.0.1.10|infra0.example.com|
|infra1|10.0.1.11|infra1.example.com|
|infra2|10.0.1.12|infra2.example.com|
Start the etcd gRPC proxy to use these static endpoints with the command:
The etcd gRPC proxy starts and listens on port 8080. It forwards client requests to one of the three endpoints provided above.
Sending requests through the proxy:
```bash
$ ETCDCTL_API=3 etcdctl --endpoints=127.0.0.1:2379 put foo bar
OK
$ ETCDCTL_API=3 etcdctl --endpoints=127.0.0.1:2379 get foo
foo
bar
```
## Client endpoint synchronization and name resolution
The proxy supports registering its endpoints for discovery by writing to a user-defined endpoint. This serves two purposes. First, it allows clients to synchronize their endpoints against a set of proxy endpoints for high availability. Second, it is an endpoint provider for etcd [gRPC naming](../dev-guide/grpc_naming.md).
Register proxy(s) by providing a user-defined prefix:
Suppose an application expects full control over the entire key space, but the etcd cluster is shared with other applications. To let all appications run without interfering with each other, the proxy can partition the etcd keyspace so clients appear to have access to the complete keyspace. When the proxy is given the flag `--namespace`, all client requests going into the proxy are translated to have a user-defined prefix on the keys. Accesses to the etcd cluster will be under the prefix and responses from the proxy will strip away the prefix; to the client, it appears as if there is no prefix at all.
To namespace a proxy, start it with `--namespace`:
etcd usually runs well with limited resources for development or testing purposes; it’s common to develop with etcd on a laptop or a cheap cloud machine. However, when running etcd clusters in production, some hardware guidelines are useful for proper administration. These suggestions are not hard rules; they serve as a good starting point for a robust production deployment. As always, deployments should be tested with simulated workloads before running in production.
## CPUs
Few etcd deployments require a lot of CPU capacity. Typical clusters need two to four cores to run smoothly.
Heavily loaded etcd deployments, serving thousands of clients or tens of thousands of requests per second, tend to be CPU bound since etcd can serve requests from memory. Such heavy deployments usually need eight to sixteen dedicated cores.
## Memory
etcd has a relatively small memory footprint but its performance still depends on having enough memory. An etcd server will aggressively cache key-value data and spends most of the rest of its memory tracking watchers. Typically 8GB is enough. For heavy deployments with thousands of watchers and millions of keys, allocate 16GB to 64GB memory accordingly.
## Disks
Fast disks are the most critical factor for etcd deployment performance and stability.
A slow disk will increase etcd request latency and potentially hurt cluster stability. Since etcd’s consensus protocol depends on persistently storing metadata to a log, a majority of etcd cluster members must write every request down to disk. Additionally, etcd will also incrementally checkpoint its state to disk so it can truncate this log. If these writes take too long, heartbeats may time out and trigger an election, undermining the stability of the cluster.
etcd is very sensitive to disk write latency. Typically 50 sequential IOPS (e.g., a 7200 RPM disk) is required. For heavily loaded clusters, 500 sequential IOPS (e.g., a typical local SSD or a high performance virtualized block device) is recommended. Note that most cloud providers publish concurrent IOPS rather than sequential IOPS; the published concurrent IOPS can be 10x greater than the sequential IOPS. To measure actual sequential IOPS, we suggest using a disk benchmarking tool such as [diskbench][diskbench] or [fio][fio].
etcd requires only modest disk bandwidth but more disk bandwidth buys faster recovery times when a failed member has to catch up with the cluster. Typically 10MB/s will recover 100MB data within 15 seconds. For large clusters, 100MB/s or higher is suggested for recovering 1GB data within 15 seconds.
When possible, back etcd’s storage with a SSD. A SSD usually provides lower write latencies and with less variance than a spinning disk, thus improving the stability and reliability of etcd. If using spinning disk, get the fastest disks possible (15,000 RPM). Using RAID 0 is also an effective way to increase disk speed, for both spinning disks and SSD. With at least three cluster members, mirroring and/or parity variants of RAID are unnecessary; etcd's consistent replication already gets high availability.
## Network
Multi-member etcd deployments benefit from a fast and reliable network. In order for etcd to be both consistent and partition tolerant, an unreliable network with partitioning outages will lead to poor availability. Low latency ensures etcd members can communicate fast. High bandwidth can reduce the time to recover a failed etcd member. 1GbE is sufficient for common etcd deployments. For large etcd clusters, a 10GbE network will reduce mean time to recovery.
Deploy etcd members within a single data center when possible to avoid latency overheads and lessen the possibility of partitioning events. If a failure domain in another data center is required, choose a data center closer to the existing one. Please also read the [tuning][tuning] documentation for more information on cross data center deployment.
## Example hardware configurations
Here are a few example hardware setups on AWS and GCE environments. As mentioned before, but must be stressed regardless, administrators should test an etcd deployment with a simulated workload before putting it into production.
Note that these configurations assume these machines are totally dedicated to etcd. Running other applications along with etcd on these machines may cause resource contentions and lead to cluster instability.
### Small cluster
A small cluster serves fewer than 100 clients, fewer than 200 of requests per second, and stores no more than 100MB of data.
Example application workload: A 50-node Kubernetes cluster
| Provider | Type | vCPUs | Memory (GB) | Max concurrent IOPS | Disk bandwidth (MB/s) |
An etcd cluster needs periodic maintenance to remain reliable. Depending on an etcd application's needs, this maintenance can usually be automated and performed without downtime or significantly degraded performance.
All etcd maintenance manages storage resources consumed by the etcd keyspace. Failure to adequately control the keyspace size is guarded by storage space quotas; if an etcd member runs low on space, a quota will trigger cluster-wide alarms which will put the system into a limited-operation maintenance mode. To avoid running out of space for writes to the keyspace, the etcd keyspace history must be compacted. Storage space itself may be reclaimed by defragmenting etcd members. Finally, periodic snapshot backups of etcd member state makes it possible to recover any unintended logical data loss or corruption caused by operational error.
## History compaction
Since etcd keeps an exact history of its keyspace, this history should be periodically compacted to avoid performance degradation and eventual storage space exhaustion. Compacting the keyspace history drops all information about keys superseded prior to a given keyspace revision. The space used by these keys then becomes available for additional writes to the keyspace.
The keyspace can be compacted automatically with `etcd`'s time windowed history retention policy, or manually with `etcdctl`. The `etcdctl` method provides fine-grained control over the compacting process whereas automatic compacting fits applications that only need key history for some length of time.
`etcd` can be set to automatically compact the keyspace with the `--auto-compaction` option with a period of hours:
```sh
# keep one hour of history
$ etcd --auto-compaction-retention=1
```
An `etcdctl` initiated compaction works as follows:
```sh
# compact up to revision 3
$ etcdctl compact 3
```
Revisions prior to the compaction revision become inaccessible:
```sh
$ etcdctl get --rev=2 somekey
Error: rpc error: code=11desc= etcdserver: mvcc: required revision has been compacted
```
## Defragmentation
After compacting the keyspace, the backend database may exhibit internal fragmentation. Any internal fragmentation is space that is free to use by the backend but still consumes storage space. The process of defragmentation releases this storage space back to the file system. Defragmentation is issued on a per-member so that cluster-wide latency spikes may be avoided.
Compacting old revisions internally fragments `etcd` by leaving gaps in backend database. Fragmented space is available for use by `etcd` but unavailable to the host filesystem.
To defragment an etcd member, use the `etcdctl defrag` command:
The space quota in `etcd` ensures the cluster operates in a reliable fashion. Without a space quota, `etcd` may suffer from poor performance if the keyspace grows excessively large, or it may simply run out of storage space, leading to unpredictable cluster behavior. If the keyspace's backend database for any member exceeds the space quota, `etcd` raises a cluster-wide alarm that puts the cluster into a maintenance mode which only accepts key reads and deletes. Only after freeing enough space in the keyspace and defragmenting the backend database, along with clearing the space quota alarm can the cluster resume normal operation.
By default, `etcd` sets a conservative space quota suitable for most applications, but it may be configured on the command line, in bytes:
```sh
# set a very small 16MB quota
$ etcd --quota-backend-bytes=$((16*1024*1024))
```
The space quota can be triggered with a loop:
```sh
# fill keyspace
$ while [ 1 ]; do dd if=/dev/urandom bs=1024 count=1024 | ETCDCTL_API=3 etcdctl put key || break; done
Snapshotting the `etcd` cluster on a regular basis serves as a durable backup for an etcd keyspace. By taking periodic snapshots of an etcd member's backend database, an `etcd` cluster can be recovered to a point in time with a known good state.
A snapshot is taken with `etcdctl`:
```sh
$ etcdctl snapshot save backup.db
$ etcdctl --write-out=table snapshot status backup.db
Each etcd server provides local monitoring information on its client port through http endpoints. The monitoring data is useful for both system health checking and cluster debugging.
## Debug endpoint
If `--debug` is set, the etcd server exports debugging information on its client port under the `/debug` path. Take care when setting `--debug`, since there will be degraded performance and verbose logging.
The `/debug/pprof` endpoint is the standard go runtime profiling endpoint. This can be used to profile CPU, heap, mutex, and goroutine utilization. For example, here `go tool pprof` gets the top 10 functions where etcd spends its time:
```sh
$ go tool pprof http://localhost:2379/debug/pprof/profile
Fetching profile from http://localhost:2379/debug/pprof/profile
Please wait... (30s)
Saved profile in /home/etcd/pprof/pprof.etcd.localhost:2379.samples.cpu.001.pb.gz
The `/debug/requests` endpoint gives gRPC traces and performance statistics through a web browser. For example, here is a `Range` request for the key `abc`:
Now Prometheus will scrape etcd metrics every 10 seconds.
### Alerting
There is a set of default alerts for etcd v3 clusters for [Prometheus 1.x](./etcd3_alert.rules) as well as [Prometheus 2.x](./etcd3_alert.rules.yml).
> Note: `job` labels may need to be adjusted to fit a particular need. The rules were written to apply to a single cluster so it is recommended to choose labels unique to a cluster.
### Grafana
[Grafana][grafana] has built-in Prometheus support; just add a Prometheus data source:
```
Name: test-etcd
Type: Prometheus
Url: http://localhost:9090
Access: proxy
```
Then import the default [etcd dashboard template][template] and customize. For instance, if Prometheus data source name is `my-etcd`, the `datasource` field values in JSON also need to be `my-etcd`.
etcd provides stable, sustained high performance. Two factors define performance: latency and throughput. Latency is the time taken to complete an operation. Throughput is the total operations completed within some time period. Usually average latency increases as the overall throughput increases when etcd accepts concurrent client requests. In common cloud environments, like a standard `n-4` on Google Compute Engine (GCE) or a comparable machine type on AWS, a three member etcd cluster finishes a request in less than one millisecond under light load, and can complete more than 30,000 requests per second under heavy load.
etcd uses the Raft consensus algorithm to replicate requests among members and reach agreement. Consensus performance, especially commit latency, is limited by two physical constraints: network IO latency and disk IO latency. The minimum time to finish an etcd request is the network Round Trip Time (RTT) between members, plus the time `fdatasync` requires to commit the data to permanant storage. The RTT within a datacenter may be as long as several hundred microseconds. A typical RTT within the United States is around 50ms, and can be as slow as 400ms between continents. The typical fdatasync latency for a spinning disk is about 10ms. For SSDs, the latency is often lower than 1ms. To increase throughput, etcd batches multiple requests together and submits them to Raft. This batching policy lets etcd attain high throughput despite heavy load.
There are other sub-systems which impact the overall performance of etcd. Each serialized etcd request must run through etcd’s boltdb-backed MVCC storage engine, which usually takes tens of microseconds to finish. Periodically etcd incrementally snapshots its recently applied requests, merging them back with the previous on-disk snapshot. This process may lead to a latency spike. Although this is usually not a problem on SSDs, it may double the observed latency on HDD. Likewise, inflight compactions can impact etcd’s performance. Fortunately, the impact is often insignificant since the compaction is staggered so it does not compete for resources with regular requests. The RPC system, gRPC, gives etcd a well-defined, extensible API, but it also introduces additional latency, especially for local reads.
## Benchmarks
Benchmarking etcd performance can be done with the [benchmark](https://github.com/coreos/etcd/tree/master/tools/benchmark) CLI tool included with etcd.
For some baseline performance numbers, we consider a three member etcd cluster with the following hardware configuration:
With this configuration, etcd can approximately write:
| Number of keys | Key size in bytes | Value size in bytes | Number of connections | Number of clients | Target etcd server | Average write QPS | Average latency per request | Average server RSS |
put --key-size=8 --sequential-keys --total=100000 --val-size=256
```
Linearizable read requests go through a quorum of cluster members for consensus to fetch the most recent data. Serializable read requests are cheaper than linearizable reads since they are served by any single etcd member, instead of a quorum of members, in exchange for possibly serving stale data. etcd can read:
| Number of requests | Key size in bytes | Value size in bytes | Number of connections | Number of clients | Consistency | Average read QPS | Average latency per request |
We encourage running the benchmark test when setting up an etcd cluster for the first time in a new environment to ensure the cluster achieves adequate performance; cluster latency and throughput can be sensitive to minor environment differences.
etcd is designed to withstand machine failures. An etcd cluster automatically recovers from temporary failures (e.g., machine reboots) and tolerates up to *(N-1)/2* permanent failures for a cluster of N members. When a member permanently fails, whether due to hardware failure or disk corruption, it loses access to the cluster. If the cluster permanently loses more than *(N-1)/2* members then it disastrously fails, irrevocably losing quorum. Once quorum is lost, the cluster cannot reach consensus and therefore cannot continue accepting updates.
To recover from disastrous failure, etcd v3 provides snapshot and restore facilities to recreate the cluster without v3 key data loss. To recover v2 keys, refer to the [v2 admin guide][v2_recover].
Recovering a cluster first needs a snapshot of the keyspace from an etcd member. A snapshot may either be taken from a live member with the `etcdctl snapshot save` command or by copying the `member/snap/db` file from an etcd data directory. For example, the following command snapshots the keyspace served by `$ENDPOINT` to the file `snapshot.db`:
```sh
$ ETCDCTL_API=3 etcdctl --endpoints $ENDPOINT snapshot save snapshot.db
```
## Restoring a cluster
To restore a cluster, all that is needed is a single snapshot "db" file. A cluster restore with `etcdctl snapshot restore` creates new etcd data directories; all members should restore using the same snapshot. Restoring overwrites some snapshot metadata (specifically, the member ID and cluster ID); the member loses its former identity. This metadata overwrite prevents the new member from inadvertently joining an existing cluster. Therefore in order to start a cluster from a snapshot, the restore must start a new logical cluster.
Snapshot integrity may be optionally verified at restore time. If the snapshot is taken with `etcdctl snapshot save`, it will have an integrity hash that is checked by `etcdctl snapshot restore`. If the snapshot is copied from the data directory, there is no integrity hash and it will only restore by using `--skip-hash-check`.
A restore initializes a new member of a new cluster, with a fresh cluster configuration using `etcd`'s cluster configuration flags, but preserves the contents of the etcd keyspace. Continuing from the previous example, the following creates new etcd data directories (`m1.etcd`, `m2.etcd`, `m3.etcd`) for a three member cluster:
etcd comes with support for incremental runtime reconfiguration, which allows users to update the membership of the cluster at run time.
Reconfiguration requests can only be processed when a majority of cluster members are functioning. It is **highly recommended** to always have a cluster size greater than two in production. It is unsafe to remove a member from a two member cluster. The majority of a two member cluster is also two. If there is a failure during the removal process, the cluster might not be able to make progress and need to [restart from majority failure][majority failure].
To better understand the design behind runtime reconfiguration, please read [the runtime reconfiguration document][runtime-reconf].
## Reconfiguration use cases
This section will walk through some common reasons for reconfiguring a cluster. Most of these reasons just involve combinations of adding or removing a member, which are explained below under [Cluster Reconfiguration Operations][cluster-reconf].
### Cycle or upgrade multiple machines
If multiple cluster members need to move due to planned maintenance (hardware upgrades, network downtime, etc.), it is recommended to modify members one at a time.
It is safe to remove the leader, however there is a brief period of downtime while the election process takes place. If the cluster holds more than 50MB of v2 data, it is recommended to [migrate the member's data directory][member migration].
### Change the cluster size
Increasing the cluster size can enhance [failure tolerance][fault tolerance table] and provide better read performance. Since clients can read from any member, increasing the number of members increases the overall serialized read throughput.
Decreasing the cluster size can improve the write performance of a cluster, with a trade-off of decreased resilience. Writes into the cluster are replicated to a majority of members of the cluster before considered committed. Decreasing the cluster size lowers the majority, and each write is committed more quickly.
### Replace a failed machine
If a machine fails due to hardware failure, data directory corruption, or some other fatal situation, it should be replaced as soon as possible. Machines that have failed but haven't been removed adversely affect the quorum and reduce the tolerance for an additional failure.
To replace the machine, follow the instructions for [removing the member][remove member] from the cluster, and then [add a new member][add member] in its place. If the cluster holds more than 50MB, it is recommended to [migrate the failed member's data directory][member migration] if it is still accessible.
### Restart cluster from majority failure
If the majority of the cluster is lost or all of the nodes have changed IP addresses, then manual action is necessary to recover safely. The basic steps in the recovery process include [creating a new cluster using the old data][disaster recovery], forcing a single member to act as the leader, and finally using runtime configuration to [add new members][add member] to this new cluster one at a time.
## Cluster reconfiguration operations
With these use cases in mind, the involved operations can be described for each.
Before making any change, a simple majority (quorum) of etcd members must be available. This is essentially the same requirement for any kind of write to etcd.
All changes to the cluster must be done sequentially:
* To update a single member peerURLs, issue an update operation
* To replace a healthy single member, remove the old member then add a new member
* To increase from 3 to 5 members, issue two add operations
* To decrease from 5 to 3, issue two remove operations
All of these examples use the `etcdctl` command line tool that ships with etcd. To change membership without `etcdctl`, use the [v2 HTTP members API][member-api] or the [v3 gRPC members API][member-api-grpc].
### Update a member
#### Update advertise client URLs
To update the advertise client URLs of a member, simply restart that member with updated client urls flag (`--advertise-client-urls`) or environment variable (`ETCD_ADVERTISE_CLIENT_URLS`). The restarted member will self publish the updated URLs. A wrongly updated client URL will not affect the health of the etcd cluster.
#### Update advertise peer URLs
To update the advertise peer URLs of a member, first update it explicitly via member command and then restart the member. The additional action is required since updating peer URLs changes the cluster wide configuration and can affect the health of the etcd cluster.
To update the advertise peer URLs, first find the target member's ID. To list all members with `etcdctl`:
This example will `update` a8266ecf031671f3 member ID and change its peerURLs value to `http://10.0.1.10:2380`:
```sh
$ etcdctl member update a8266ecf031671f3 --peer-urls=http://10.0.1.10:2380
Updated member with ID a8266ecf031671f3 in cluster
```
### Remove a member
Suppose the member ID to remove is a8266ecf031671f3. Use the `remove` command to perform the removal:
```sh
$ etcdctl member remove a8266ecf031671f3
Removed member a8266ecf031671f3 from cluster
```
The target member will stop itself at this point and print out the removal in the log:
```
etcd: this member has been permanently removed from the cluster. Exiting.
```
It is safe to remove the leader, however the cluster will be inactive while a new leader is elected. This duration is normally the period of election timeout plus the voting process.
### Add a new member
Adding a member is a two step process:
* Add the new member to the cluster via the [HTTP members API][member-api], the [gRPC members API][member-api-grpc], or the `etcdctl member add` command.
* Start the new member with the new cluster configuration, including a list of the updated members (existing members + the new member).
`etcdctl` adds a new member to the cluster by specifying the member's [name][conf-name] and [advertised peer URLs][conf-adv-peer]:
`etcdctl` has informed the cluster about the new member and printed out the environment variables needed to successfully start it. Now start the new etcd process with the relevant flags for the new member:
The new member will run as a part of the cluster and immediately begin catching up with the rest of the cluster.
If adding multiple members the best practice is to configure a single member at a time and verify it starts correctly before adding more new members. If adding a new member to a 1-node cluster, the cluster cannot make progress before the new member starts because it needs two members as majority to agree on the consensus. This behavior only happens between the time `etcdctl member add` informs the cluster about the new member and the new member successfully establishing a connection to the existing one.
#### Error cases when adding members
In the following case a new host is not included in the list of enumerated nodes. If this is a new cluster, the node must be added to the list of initial cluster members.
As described in the above, the best practice of adding new members is to configure a single member at a time and verify it starts correctly before adding more new members. This step by step approach is very important because if newly added members is not configured correctly (for example the peer URLs are incorrect), the cluster can lose quorum. The quorum loss happens since the newly added member are counted in the quorum even if that member is not reachable from other existing members. Also quorum loss might happen if there is a connectivity issue or there are operational issues.
For avoiding this problem, etcd provides an option `-strict-reconfig-check`. If this option is passed to etcd, etcd rejects reconfiguration requests if the number of started members will be less than a quorum of the reconfigured cluster.
Runtime reconfiguration is one of the hardest and most error prone features in a distributed system, especially in a consensus based system like etcd.
Read on to learn about the design of etcd's runtime reconfiguration commands and how we tackled these problems.
## Two phase config changes keep the cluster safe
In etcd, every runtime reconfiguration has to go through [two phases][add-member] for safety reasons. For example, to add a member, first inform cluster of new configuration and then start the new member.
Phase 1 - Inform cluster of new configuration
To add a member into etcd cluster, make an API call to request a new member to be added to the cluster. This is the only way to add a new member into an existing cluster. The API call returns when the cluster agrees on the configuration change.
Phase 2 - Start new member
To join the new etcd member into the existing cluster, specify the correct `initial-cluster` and set `initial-cluster-state` to `existing`. When the member starts, it will contact the existing cluster first and verify the current cluster configuration matches the expected one specified in `initial-cluster`. When the new member successfully starts, the cluster has reached the expected configuration.
By splitting the process into two discrete phases users are forced to be explicit regarding cluster membership changes. This actually gives users more flexibility and makes things easier to reason about. For example, if there is an attempt to add a new member with the same ID as an existing member in an etcd cluster, the action will fail immediately during phase one without impacting the running cluster. Similar protection is provided to prevent adding new members by mistake. If a new etcd member attempts to join the cluster before the cluster has accepted the configuration change, it will not be accepted by the cluster.
Without the explicit workflow around cluster membership etcd would be vulnerable to unexpected cluster membership changes. For example, if etcd is running under an init system such as systemd, etcd would be restarted after being removed via the membership API, and attempt to rejoin the cluster on startup. This cycle would continue every time a member is removed via the API and systemd is set to restart etcd after failing, which is unexpected.
We expect runtime reconfiguration to be an infrequent operation. We decided to keep it explicit and user-driven to ensure configuration safety and keep the cluster always running smoothly under explicit control.
## Permanent loss of quorum requires new cluster
If a cluster permanently loses a majority of its members, a new cluster will need to be started from an old data directory to recover the previous state.
It is entirely possible to force removing the failed members from the existing cluster to recover. However, we decided not to support this method since it bypasses the normal consensus committing phase, which is unsafe. If the member to remove is not actually dead or force removed through different members in the same cluster, etcd will end up with a diverged cluster with same clusterID. This is very dangerous and hard to debug/fix afterwards.
With a correct deployment, the possibility of permanent majority lose is very low. But it is a severe enough problem that worth special care. We strongly suggest reading the [disaster recovery documentation][disaster-recovery] and preparing for permanent majority lose before putting etcd into production.
## Do not use public discovery service for runtime reconfiguration
The public discovery service should only be used for bootstrapping a cluster. To join member into an existing cluster, use runtime reconfiguration API.
Discovery service is designed for bootstrapping an etcd cluster in the cloud environment, when the IP addresses of all the members are not known beforehand. After successfully bootstrapping a cluster, the IP addresses of all the members are known. Technically, the discovery service should no longer be needed.
It seems that using public discovery service is a convenient way to do runtime reconfiguration, after all discovery service already has all the cluster configuration information. However relying on public discovery service brings troubles:
1. it introduces external dependencies for the entire life-cycle of the cluster, not just bootstrap time. If there is a network issue between the cluster and public discovery service, the cluster will suffer from it.
2. public discovery service must reflect correct runtime configuration of the cluster during it life-cycle. It has to provide security mechanism to avoid bad actions, and it is hard.
3. public discovery service has to keep tens of thousands of cluster configurations. Our public discovery service backend is not ready for that workload.
To have a discovery service that supports runtime reconfiguration, the best choice is to build a private one.
etcd supports automatic TLS as well as authentication through client certificates for both clients to server as well as peer (server to server / cluster) communication.
To get up and running, first have a CA certificate and a signed key pair for one member. It is recommended to create and sign a new key pair for every member in a cluster.
For convenience, the [cfssl] tool provides an easy interface to certificate generation, and we provide an example using the tool [here][tls-setup]. Alternatively, try this [guide to generating self-signed key pairs][tls-guide].
## Basic setup
etcd takes several certificate related configuration options, either through command-line flags or environment variables:
**Client-to-server communication:**
`--cert-file=<path>`: Certificate used for SSL/TLS connections **to** etcd. When this option is set, advertise-client-urls can use the HTTPS schema.
`--key-file=<path>`: Key for the certificate. Must be unencrypted.
`--client-cert-auth`: When this is set etcd will check all incoming HTTPS requests for a client certificate signed by the trusted CA, requests that don't supply a valid client certificate will fail. If [authentication][auth] is enabled, the certificate provides credentials for the user name given by the Common Name field.
The peer options work the same way as the client-to-server options:
`--peer-cert-file=<path>`: Certificate used for SSL/TLS connections between peers. This will be used both for listening on the peer address as well as sending requests to other peers.
`--peer-key-file=<path>`: Key for the certificate. Must be unencrypted.
`--peer-client-cert-auth`: When set, etcd will check all incoming peer requests from the cluster for valid client certificates signed by the supplied CA.
`--peer-auto-tls`: Use automatically generated self-signed certificates for TLS connections between peers.
If either a client-to-server or peer certificate is supplied the key must also be set. All of these configuration options are also available through the environment variables, `ETCD_CA_FILE`, `ETCD_PEER_CA_FILE` and so on.
## Example 1: Client-to-server transport security with HTTPS
For this, have a CA certificate (`ca.crt`) and signed key pair (`server.crt`, `server.key`) ready.
Let us configure etcd to provide simple HTTPS transport security step by step:
The command should show that the handshake succeed. Since we use self-signed certificates with our own certificate authority, the CA must be passed to curl using the `--cacert` option. Another possibility would be to add the CA certificate to the system's trusted certificates directory (usually in `/etc/pki/tls/certs` or `/etc/ssl/certs`).
**OSX 10.9+ Users**: curl 7.30.0 on OSX 10.9+ doesn't understand certificates passed in on the command line.
Instead, import the dummy ca.crt directly into the keychain or add the `-k` flag to curl to ignore errors.
To test without the `-k` flag, run `open ./fixtures/ca/ca.crt` and follow the prompts.
Please remove this certificate after testing!
If there is a workaround, let us know.
## Example 2: Client-to-server authentication with HTTPS client certificates
For now we've given the etcd client the ability to verify the server identity and provide transport security. We can however also use client certificates to prevent unauthorized access to etcd.
The clients will provide their certificates to the server and the server will check whether the cert is signed by the supplied CA and decide whether to serve the request.
The same files mentioned in the first example are needed for this, as well as a key pair for the client (`client.crt`, `client.key`) signed by the same certificate authority.
## Example 3: Transport security & client certificates in a cluster
etcd supports the same model as above for **peer communication**, that means the communication between etcd members in a cluster.
Assuming we have our `ca.crt` and two members with their own keypairs (`member1.crt`&`member1.key`, `member2.crt`&`member2.key`) signed by this CA, we launch etcd as follows:
```sh
DISCOVERY_URL=... # from https://discovery.etcd.io/new
The etcd members will form a cluster and all communication between members in the cluster will be encrypted and authenticated using the client certificates. The output of etcd will show that the addresses it connects to use HTTPS.
## Example 4: Automatic self-signed transport security
For cases where communication encryption, but not authentication, is needed, etcd supports encrypting its messages with automatically generated self-signed certificates. This simplifies deployment because there is no need for managing certificates and keys outside of etcd.
Configure etcd to use self-signed certificates for client and peer connections with the flags `--auto-tls` and `--peer-auto-tls`:
```sh
DISCOVERY_URL=... # from https://discovery.etcd.io/new
Since v3.1.0 (except v3.2.9), discovery SRV bootstrapping authenticates `ServerName` with a root domain name from `--discovery-srv` flag. This is to avoid man-in-the-middle cert attacks, by requiring a certificate to have matching root domain name in its Subject Alternative Name (SAN) field. For instance, `etcd --discovery-srv=etcd.local` will only authenticate peers/clients when the provided certs have root domain `etcd.local` as an entry in Subject Alternative Name (SAN) field
## Notes for etcd proxy
etcd proxy terminates the TLS from its client if the connection is secure, and uses proxy's own key/cert specified in `--peer-key-file` and `--peer-cert-file` to communicate with etcd members.
The proxy communicates with etcd members through both the `--advertise-client-urls` and `--advertise-peer-urls` of a given member. It forwards client requests to etcd members’ advertised client urls, and it syncs the initial cluster configuration through etcd members’ advertised peer urls.
When client authentication is enabled for an etcd member, the administrator must ensure that the peer certificate specified in the proxy's `--peer-cert-file` option is valid for that authentication. The proxy's peer certificate must also be valid for peer authentication if peer authentication is enabled.
## Frequently asked questions
### I'm seeing a SSLv3 alert handshake failure when using TLS client authentication?
The `crypto/tls` package of `golang` checks the key usage of the certificate public key before using it.
To use the certificate public key to do client auth, we need to add `clientAuth` to `Extended Key Usage` when creating the certificate public key.
Here is how to do it:
Add the following section to openssl.cnf:
```
[ ssl_client ]
...
extendedKeyUsage = clientAuth
...
```
When creating the cert be sure to reference it in the `-extensions` flag:
### With peer certificate authentication I receive "certificate is valid for 127.0.0.1, not $MY_IP"
Make sure to sign the certificates with a Subject Name the member's public IP address. The `etcd-ca` tool for example provides an `--ip=` option for its `new-cert` command.
The certificate needs to be signed for the member's FQDN in its Subject Name, use Subject Alternative Names (short IP SANs) to add the IP address. The `etcd-ca` tool provides `--domain=` option for its `new-cert` command, and openssl can make [it][alt-name] too.
* etcd-maintainers are listed in https://github.com/coreos/etcd/blob/master/MAINTAINERS.
Experimental platforms appear to work in practice and have some platform specific code in etcd, but do not fully conform to the stable support policy. Unstable platforms have been lightly tested, but less than experimental. Unlisted architecture and operating system pairs are currently unsupported; caveat emptor.
## Supporting a new system platform
For etcd to officially support a new platform as stable, a few requirements are necessary to ensure acceptable quality:
1. An "official" maintainer for the platform with clear motivation; someone must be responsible for taking care of the platform.
2. Set up CI for build; etcd must compile.
3. Set up CI for running unit tests; etcd must pass simple tests.
4. Set up CI (TravisCI, SemaphoreCI or Jenkins) for running integration tests; etcd must pass intensive tests.
5. (Optional) Set up a functional testing cluster; an etcd cluster should survive stress testing.
## 32-bit and other unsupported systems
etcd has known issues on 32-bit systems due to a bug in the Go runtime. See the [Go issue][go-issue] and [atomic package][go-atomic] for more information.
To avoid inadvertently running a possibly unstable etcd server, `etcd` on unstable or unsupported architectures will print a warning message and immediately exit if the environment variable `ETCD_UNSUPPORTED_ARCH` is not set to the target architecture.
Currently amd64 and ppc64le architectures are officially supported by `etcd`.
# Migrate applications from using API v2 to API v3
The data store v2 is still accessible from the API v2 after upgrading to etcd3. Thus, it will work as before and require no application changes. With etcd 3, applications use the new grpc API v3 to access the mvcc store, which provides more features and improved performance. The mvcc store and the old store v2 are separate and isolated; writes to the store v2 will not affect the mvcc store and, similarly, writes to the mvcc store will not affect the store v2.
Migrating an application from the API v2 to the API v3 involves two steps: 1) migrate the client library and, 2) migrate the data. If the application can rebuild the data, then migrating the data is unnecessary.
## Migrate client library
API v3 is different from API v2, thus application developers need to use a new client library to send requests to etcd API v3. The documentation of the client v3 is available at https://godoc.org/github.com/coreos/etcd/clientv3.
There are some notable differences between API v2 and API v3:
- Transaction: In v3, etcd provides multi-key conditional transactions. Applications should use transactions in place of `Compare-And-Swap` operations.
- Flat key space: There are no directories in API v3, only keys. For example, "/a/b/c/" is a key. Range queries support getting all keys matching a given prefix.
- Compacted responses: Operations like `Delete` no longer return previous values. To get the deleted value, a transaction can be used to atomically get the key and then delete its value.
- Leases: A replacement for v2 TTLs; the TTL is bound to a lease and keys attach to the lease. When the TTL expires, the lease is revoked and all attached keys are removed.
## Migrate data
Application data can be migrated either offline or online. Offline migration is much simpler than online migration and is recommended.
Sometimes an etcd cluster will possibly have v3 data which should not be overwritten. In this case, the migration process may want to confirm no v3 data is committed before proceeding. One way to check the cluster has no v3 keys is to issue the following `etcdctl` command, which scans the entire v3 keyspace for any key, expecting `0` as output:
```sh
ETCDCTL_API=3 etcdctl get "" --from-key --keys-only --limit 1| wc -l
```
### Offline migration
Offline migration is very simple but requires etcd downtime. If an etcd downtime window spanning from seconds to minutes is acceptable, offline migration is a good choice and is easy to automate.
First, all members in the etcd cluster must converge to the same state. This can be achieved by stopping all applications that write keys to etcd. Alternatively, if the applications must remain running, configure etcd to listen on a different client URL and restart all etcd members. To check if the states converged, within a few seconds, use the `ETCDCTL_API=3 etcdctl endpoint status` command to confirm that the `raft index` of all members match (or differ by at most 1 due to an internal sync raft command).
Second, migrate the v2 keys into v3 with the [migrate][migrate_command] (`ETCDCTL_API=3 etcdctl migrate`) command. The migrate command writes keys in the v2 store to a user-provided transformer program and reads back transformed keys. It then writes transformed keys into the mvcc store. This usually takes at most tens of seconds.
Restart the etcd members and everything should just work.
For etcd v3.3+, run `ETCDCTL_API=3 etcdctl endpoint hashkv --cluster` to ensure key-value stores are consistent post migration.
**Warn**: When v2 store has expiring TTL keys and migrate command intends to preserve TTLs, migration may be inconsistent with the last committed v2 state when run on any member with a raft index less than the last leader's raft index.
### Online migration
If the application cannot tolerate any downtime, then it must migrate online. The implementation of online migration will vary from application to application but the overall idea is the same.
First, write application code using the v3 API. The application must support two modes: a migration mode and a normal mode. The application starts in migration mode. When running in migration mode, the application reads keys using the v3 API first, and, if it cannot find the key, it retries with the API v2. In normal mode, the application only reads keys using the v3 API. The application writes keys over the API v3 in both modes. To acknowledge a switch from migration mode to normal mode, the application watches on a switch mode key. When switch key’s value turns to `true`, the application switches over from migration mode to normal mode.
Second, start a background job to migrate data from the store v2 to the mvcc store by reading keys from the API v2 and writing keys to the API v3.
After finishing data migration, the background job writes `true` into the switch mode key to notify the application that it may switch modes.
Online migration can be difficult when the application logic depends on store v2 indexes. Applications will need additional logic to convert mvcc store revisions to store v2 indexes.
This guide assumes operational knowledge of Amazon Web Services (AWS), specifically Amazon Elastic Compute Cloud (EC2). This guide provides an introduction to design considerations when designing an etcd deployment on AWS EC2 and how AWS specific features may be utilized in that context.
## Capacity planning
As a critical building block for distributed systems it is crucial to perform adequate capacity planning in order to support the intended cluster workload. As a highly available and strongly consistent data store increasing the number of nodes in an etcd cluster will generally affect performance adversely. This makes sense intuitively, as more nodes means more members for the leader to coordinate state across. The most direct way to increase throughput and decrease latency of an etcd cluster is allocate more disk I/O, network I/O, CPU, and memory to cluster members. In the event it is impossible to temporarily divert incoming requests to the cluster, scaling the EC2 instances which comprise the etcd cluster members one at a time may improve performance. It is, however, best to avoid bottlenecks through capacity planning.
The etcd team has produced a [hardware recommendation guide](../op-guide/hardware.md) which is very useful for “ballparking” how many nodes and what instance type are necessary for a cluster.
AWS provides a service for creating groups of EC2 instances which are dynamically sized to match load on the instances. Using an Auto Scaling Group ([ASG](http://docs.aws.amazon.com/autoscaling/latest/userguide/AutoScalingGroup.html)) to dynamically scale an etcd cluster is not recommended for several reasons including:
* etcd performance is generally inversely proportional to the number of members in a cluster due to the synchronous replication which provides strong consistency of data stored in etcd
* the operational complexity of adding [lifecycle hooks](http://docs.aws.amazon.com/autoscaling/latest/userguide/lifecycle-hooks.html) to properly add and remove members from an etcd cluster by modifying the [runtime configuration](../op-guide/runtime-configuration.md)
Auto Scaling Groups do provide a number of benefits besides cluster scaling which include:
* distribution of EC2 instances across Availability Zones (AZs)
* EC2 instance fail over across AZs
* consolidated monitoring and life cycle control of instances within an ASG
The use of an ASG to create a [self healing etcd cluster](#self-healing) is one of the design considerations when deploying an etcd cluster to AWS.
## Cluster design
The purpose of this section is to provide foundational guidance for deploying etcd on AWS. The discussion will be framed by the following three critical design criteria about the etcd cluster itself:
* block device provider: limited to the tradeoffs between EBS or instance storage (InstanceStore)
* cluster topology: how many nodes should make up an etcd cluster; should these nodes be distributed over multiple AZs
* managing etcd members: creating a static cluster of EC2 instances or using an ASG.
The intended cluster workload should dictate the cluster design. A configuration store for microservices may require different design considerations than a distributed lock service, a secrets store, or a Kubernetes control plane. Cluster design tradeoffs include considerations such as:
* availability
* data durability after member failure
* performance/throughput
* self healing
### Availability
Instance availability on AWS is ultimately determined by the Amazon EC2 Region Service Level Agreement ([SLA](https://aws.amazon.com/ec2/sla/)) which is the policy by which Amazon describes their precise definition of a regional outage.
In the context of an etcd cluster this means a cluster must contain a minimum of three members where EC2 instances are spread across at least two AZs in order for an etcd cluster to be considered highly available at a Regional level.
For most use cases the additional latency associated with a cluster spanning across Availability Zones will introduce a negligible performance impact.
Availability considerations apply to all components of an application; if the application which accesses the etcd cluster will only be deployed to a single Availability Zone it may not make sense to make the etcd cluster highly available across zones.
### Data durability after member failure
A highly available etcd cluster is resilient to member loss, however, it is important to consider data durability in the event of disaster when designing an etcd deployment. Deploying etcd on AWS supports multiple mechanisms for data durability.
* replication: etcd replicates all data to all members of the etcd cluster. Therefore, given more members in the cluster and more independent failure domains, the less likely that data stored in an etcd cluster will be permanently lost in the event of disaster.
* Point in time etcd snapshotting: the etcd v3 API introduced support for snapshotting clusters. The operation is cheap enough (completing in the order of minutes) to run quite frequently and the resulting archives can be archived in a storage service like Amazon Simple Storage Service (S3).
* Amazon Elastic Block Storage (EBS): an EBS volume is a replicated network attached block device which have stronger storage safety guarantees than InstanceStore which has a life cycle associated with the life cycle of the attached EC2 instance. The life cycle of an EBS volume is not necessarily tied to an EC2 instance and can be detached and snapshotted independently which means that a single node etcd cluster backed by an EBS volume can provide a fairly reasonable level of data durability.
### Performance/Throughput
The performance of an etcd cluster is roughly quantifiable through latency and throughput metrics which are primarily affected by disk and network performance. Detailed performance planning information is provided in the [performance section](../op-guide/performance.md) of the etcd operations guide.
#### Network
AWS offers EC2 Placement Groups which allow the collocation of EC2 instances within a single Availability Zone which can be utilized in order to minimize network latency between etcd members in the cluster. It is important to remember that collocation of etcd nodes within a single AZ will provide weaker fault tolerance than distributing members across multiple AZs. [Enhanced networking for EC2 instances](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/enhanced-networking.html) may also improve network performance of individual EC2 instances.
#### Disk
AWS provides two basic types of block storage: [EBS volumes](https://aws.amazon.com/ebs/) and [EC2 Instance Store](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html). As mentioned, an EBS volume is a network attached block device while instance storage is directly attached to the hypervisor of the EC2 host. EBS volumes will generally have higher latency, lower throughput, and greater performance variance than Instance Store volumes. If performance, rather than data safety, is the primary concern it is highly recommended that instance storage on the EC2 instances be utilized. Remember that the amount of available instance storage varies by EC2 [instance types](https://aws.amazon.com/ec2/instance-types/) which may impose additional performance considerations.
Inconsistent EBS volume performance can introduce etcd cluster instability. [Provisioned IOPS](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSVolumeTypes.html#EBSVolumeTypes_piops) can provide more consistent performance than general purpose SSD EBS volumes. More information about EBS volume performance is available [from AWS](https://aws.amazon.com/ebs/details/) and Datadog has shared their experience with [getting optimal performance with AWS EBS Provisioned IOPS](https://www.datadoghq.com/blog/aws-ebs-provisioned-iops-getting-optimal-performance/) in their engineering blog.
### Self healing
While using an ASG to scale the size of an etcd cluster is not recommended, an ASG can be used effectively to maintain the desired number of nodes in the event of node failure. The maintenance of a stable number of etcd nodes will provide the etcd cluster with a measure of self healing.
### Next steps
The operational life cycle of an etcd cluster can be greatly simplified through the use of the etcd-operator. The open source etcd operator is a Kubernetes control plane operator which deploys and manages etcd clusters atop Kubernetes. While still in its early stages the etcd-operator already offers periodic backups to S3, detection and replacement of failed nodes, and automated disaster recovery from backups in the event of permanent quorum loss.
The following guide shows how to run etcd with [systemd][systemd-docs] under [Container Linux][container-linux-docs].
## Provisioning an etcd cluster
Cluster bootstrapping in Container Linux is simplest with [Ignition][container-linux-ignition]; `coreos-metadata.service` dynamically fetches the machine's IP for discovery. Note that etcd's discovery service protocol is only meant for bootstrapping, and cannot be used with runtime reconfiguration or cluster monitoring.
The [Container Linux Config Transpiler][container-linux-ct] compiles etcd configuration files into Ignition configuration files:
See [Container Linux Provisioning][container-linux-provision] for more details.
## etcd 3.x service
[Container Linux][container-linux-docs] does not include etcd 3.x binaries by default. Different versions of etcd 3.x can be fetched via `etcd-member.service`.
Confirm unit file exists:
```
systemctl cat etcd-member.service
```
Check if the etcd service is running:
```
systemctl status etcd-member.service
```
Example systemd drop-in unit to override the default service settings:
To see all runtime drop-in changes for system units:
```
systemd-delta --type=extended
```
To enable and start:
```
systemctl daemon-reload
systemctl enable --now etcd-member.service
```
To see the logs:
```
journalctl --unit etcd-member.service --lines 10
```
To stop and disable the service:
```
systemctl disable --now etcd-member.service
```
## etcd 2.x service
[Container Linux][container-linux-docs] includes a unit file `etcd2.service` for etcd 2.x, which will be removed in the near future. See [Container Linux FAQ][container-linux-faq] for more details.
Startingwithversion0.1.2bothetcdandetcdctlhavebeenportedtoFreeBSDandcan beinstalledeitherviapackagesorportssystem.Theirversionshavebeenrecently updatedto0.2.0sonowetcd and etcdctl can be enjoyedonFreeBSD10.0(RC4as ofnow)and9.x,wheretheyhavebeentested.Theymightalsoworkwheninstalledfrom portsonearlierversionsofFreeBSD,butit is untested; caveat emptor.
## Installation
### Usingpkgngpackagesystem
1.Ifpkgng is notinstalled,installitwithcommand`pkg`andanswering'Y' whenasked.
5.etcdandetcdctl are ready to use!Formoreinformationaboutusingportssystem, pleasesee:https://www.freebsd.org/doc/handbook/portsusing.html
## Issues
Ifthere are anyissueswiththebuild/installprocedureorthere's aproblemthat islocaltoFreeBSDonly(forexample,bynotbeingableto reproduceit on any otherplatform,like OSX or Linux),pleasesend a problemreportusing thispage for more information:http://www.freebsd.org/sendpr.html
This document tracks people and use cases for etcd in production. By creating a list of production use cases we hope to build a community of advisors that we can reach out to with experience using various etcd applications, operation environments, and cluster sizes. The etcd development team may reach out periodically to check-in on how etcd is working in the field and update this list.
## All Kubernetes Users
- *Application*: https://kubernetes.io/
- *Environments*: AWS, OpenStack, Azure, Google Cloud, Huawei Cloud, Bare Metal, etc
**This is a meta user; please feel free to document specific Kubernetes clusters!**
All Kubernetes clusters use etcd as their primary data store. This means etcd's users include such companies as [Niantic, Inc Pokemon Go](https://cloudplatform.googleblog.com/2016/09/bringing-Pokemon-GO-to-life-on-Google-Cloud.html), [Box](https://blog.box.com/blog/kubernetes-box-microservices-maximum-velocity/), [CoreOS](https://coreos.com/tectonic), [Ticketmaster](https://www.youtube.com/watch?v=wqXVKneP0Hg), [Salesforce](https://www.salesforce.com) and many many more.
discovery.etcd.io is the longest continuously running etcd backed service that we know about. It is the basis of automatic cluster bootstrap and was launched in Feb. 2014: https://coreos.com/blog/etcd-0.3.0-released/.
## OpenTable
- *Application*: OpenTable internal service discovery and cluster configuration management
- *Launched*: May 2014
- *Cluster Size*: 3 members each in 6 independent clusters; approximately 50 nodes reading / writing
- *Backups*: Periodic sync to Ceph RadosGW and DigitalOcean VM
CyCore Systems provides architecture and engineering for computing systems. This cluster provides microservices, virtual machines, databases, storage clusters to a number of clients. It is built on CoreOS machines, with each machine in the cluster running etcd as a peer or proxy.
## Radius Intelligence
- *Application*: multiple internal tools, Kubernetes clusters, bootstrappable system configs
- *Launched*: June 2015
- *Cluster Size*: 2 clusters of 5 and 3 members; approximately a dozen nodes read/write
- *Backups*: None, all data can be recreated if necessary.
Radius Intelligence uses Kubernetes running CoreOS to containerize and scale internal toolsets. Examples include running [JetBrains TeamCity][teamcity] and internal AWS security and cost reporting tools. etcd clusters back these clusters as well as provide some basic environment bootstrapping configuration keys.
## Vonage
- *Application*: kubernetes, vault backend, system configuration for microservices, scheduling, locks (future - service discovery)
- *Launched*: August 2015
- *Cluster Size*: 2 clusters of 5 members in 2 DCs, n local proxies 1-to-1 with microservice, (ssl and SRV look up)
- *Order of Data Size*: kilobytes
- *Operator*: Vonage [devAdmin][raoofm]
- *Environment*: VMWare, AWS
- *Backups*: Daily snapshots on VMs. Backups done for upgrades.
## PD
- *Application*: embed etcd
- *Launched*: Mar 2016
- *Cluster Size*: 3 or 5 members
- *Order of Data Size*: megabytes
- *Operator*: PingCAP, Inc.
- *Environment*: Bare Metal, AWS, etc.
- *Backups*: None.
PD(Placement Driver) is the central controller in the TiDB cluster. It saves the cluster meta information, schedule the data, allocate the global unique timestamp for the distributed transaction, etc. It embeds etcd to supply high availability and auto failover.
## Huawei
- *Application*: System configuration for overlay network (Canal)
- *Backups*: None, all data can be recreated if necessary.
[teamcity]: https://www.jetbrains.com/teamcity/
[raoofm]:https://github.com/raoofm
## Qiniu Cloud
- *Application*: system configuration for microservices, distributed locks
- *Launched*: Jan. 2016
- *Cluster Size*: 3 members each with several clusters
- *Order of Data Size*: kilobytes
- *Operator*: Pandora, chenchao@qiniu.com
- *Environment*: Baremetal
- *Backups*: None, all data can be recreated if necessary
## QingCloud
- *Application*: [QingCloud][qingcloud] appcenter cluster for service discovery as [metad][metad] backend.
- *Launched*: December 2016
- *Cluster Size*: 1 cluster of 3 members per user.
- *Order of Data Size*: kilobytes
- *Operator*: [yunify][yunify]
- *Environment*: QingCloud IaaS
- *Backups*: None, all data can be recreated if necessary.
[metad]:https://github.com/yunify/metad
[yunify]:https://github.com/yunify
[qingcloud]:https://qingcloud.com/
## Yandex
- *Application*: system configuration for services, service discovery
- *Launched*: March 2016
- *Cluster Size*: 3 clusters of 5 members
- *Order of Data Size*: several gigabytes
- *Operator*: Yandex; [nekto0n][nekto0n]
- *Environment*: Bare Metal
- *Backups*: None
[nekto0n]:https://github.com/nekto0n
## Tencent Games
- *Application*: Meta data and configuration data for service discovery, Kubernetes, etc.
- *Launched*: Jan. 2015
- *Cluster Size*: 3 members each with 10s of clusters
- *Order of Data Size*: 10s of Megabytes
- *Operator*: Tencent Game Operations Department
- *Environment*: Baremetal
- *Backups*: Periodic sync to backup server
In Tencent games, we use Docker and Kubernetes to deploy and run our applications, and use etcd to save meta data for service discovery, Kubernetes, etc.
## Hyper.sh
- *Application*: Kubernetes, distributed locks, etc.
- *Launched*: April 2016
- *Cluster Size*: 1 cluster of 3 members
- *Order of Data Size*: 10s of MB
- *Operator*: Hyper.sh
- *Environment*: Baremetal
- *Backups*: None, all data can be recreated if necessary.
In [hyper.sh][hyper.sh], the container service is backed by [hypernetes][hypernetes], a multi-tenant kubernetes distro. Moreover, we use etcd to coordinate the multiple manage services and store global meta data.
If any part of the etcd project has bugs or documentation mistakes, please let us know by [opening an issue][etcd-issue]. We treat bugs and mistakes very seriously and believe no issue is too small. Before creating a bug report, please check that an issue reporting the same problem does not already exist.
To make the bug report accurate and easy to understand, please try to create bug reports that are:
- Specific. Include as much details as possible: which version, what environment, what configuration, etc. If the bug is related to running the etcd server, please attach the etcd log (the starting log with etcd configuration is especially important).
- Reproducible. Include the steps to reproduce the problem. We understand some issues might be hard to reproduce, please includes the steps that might lead to the problem. If possible, please attach the affected etcd data dir and stack strace to the bug report.
- Isolated. Please try to isolate and reproduce the bug with minimum dependencies. It would significantly slow down the speed to fix a bug if too many dependencies are involved in a bug report. Debugging external systems that rely on etcd is out of scope, but we are happy to provide guidance in the right direction or help with using etcd itself.
- Unique. Do not duplicate existing bug report.
- Scoped. One bug per report. Do not follow up with another bug inside one report.
It may be worthwhile to read [Elika Etemad’s article on filing good bug reports][filing-good-bugs] before creating a bug report.
We might ask for further information to locate a bug. A duplicated bug report will be closed.
## Frequently asked questions
### How to get a stack trace
``` bash
$ kill -QUIT $PID
```
### How to get etcd version
``` bash
$ etcd --version
```
### How to get etcd configuration and log when it runs as systemd service ‘etcd2.service’
``` bash
$ sudo systemctl cat etcd2
$ sudo journalctl -u etcd2
```
Due to an upstream systemd bug, journald may miss the last few log lines when its processes exit. If journalctl says etcd stopped without fatal or panic message, try `sudo journalctl -f -t etcd2` to get full log.
The etcd v3 API is designed to give users a more efficient and cleaner abstraction compared to etcd v2. There are a number of semantic and protocol changes in this new API. For an overview [see Xiang Li's video](https://youtu.be/J5AioGtEPeQ?t=211).
To prove out the design of the v3 API the team has also built [a number of example recipes](https://github.com/coreos/etcd/tree/master/contrib/recipes), there is a [video discussing these recipes too](https://www.youtube.com/watch?v=fj-2RY-3yVU&feature=youtu.be&t=590).
# Design
1. Flatten binary key-value space
2. Keep the event history until compaction
- access to old version of keys
- user controlled history compaction
3. Support range query
- Pagination support with limit argument
- Support consistency guarantee across multiple range queries
4. Replace TTL key with Lease
- more efficient/ low cost keep alive
- a logical group of TTL keys
5. Replace CAS/CAD with multi-object Txn
- MUCH MORE powerful and flexible
6. Support efficient watching with multiple ranges
7. RPC API supports the completed set of APIs.
- more efficient than JSON/HTTP
- additional txn/lease support
8. HTTP API supports a subset of APIs.
- easy for people to try out etcd
- easy for people to write simple etcd application
## Notes
### Request Size Limitation
The max request size is around 1MB. Since etcd replicates requests in a streaming fashion, a very large
request might block other requests for a long time. The use case for etcd is to store small configuration
values, so we prevent user from submitting large requests. This also applies to Txn requests. We might loosen
the size in the future a little bit or make it configurable.
## Protobuf Defined API
[api protobuf][api-protobuf]
[kv protobuf][kv-protobuf]
## Examples
### Put a key (foo=bar)
```
// A put is always successful
Put( PutRequest { key = foo, value = bar } )
PutResponse {
cluster_id = 0x1000,
member_id = 0x1,
revision = 1,
raft_term = 0x1,
}
```
### Get a key (assume we have foo=bar)
```
Get ( RangeRequest { key = foo } )
RangeResponse {
cluster_id = 0x1000,
member_id = 0x1,
revision = 1,
raft_term = 0x1,
kvs = {
{
key = foo,
value = bar,
create_revision = 1,
mod_revision = 1,
version = 1;
},
},
}
```
### Range over a key space (assume we have foo0=bar0… foo100=bar100)
The default settings in etcd should work well for installations on a local network where the average network latency is low. However, when using etcd across multiple data centers or over networks with high latency, the heartbeat interval and election timeout settings may need tuning.
The network isn't the only source of latency. Each request and response may be impacted by slow disks on both the leader and follower. Each of these timeouts represents the total time from request to successful response from the other machine.
## Time parameters
The underlying distributed consensus protocol relies on two separate time parameters to ensure that nodes can handoff leadership if one stalls or goes offline. The first parameter is called the *Heartbeat Interval*. This is the frequency with which the leader will notify followers that it is still the leader.
For best practices, the parameter should be set around round-trip time between members. By default, etcd uses a `100ms` heartbeat interval.
The second parameter is the *Election Timeout*. This timeout is how long a follower node will go without hearing a heartbeat before attempting to become leader itself. By default, etcd uses a `1000ms` election timeout.
Adjusting these values is a trade off. The value of heartbeat interval is recommended to be around the maximum of average round-trip time (RTT) between members, normally around 0.5-1.5x the round-trip time. If heartbeat interval is too low, etcd will send unnecessary messages that increase the usage of CPU and network resources. On the other side, a too high heartbeat interval leads to high election timeout. Higher election timeout takes longer time to detect a leader failure. The easiest way to measure round-trip time (RTT) is to use [PING utility][ping].
The election timeout should be set based on the heartbeat interval and average round-trip time between members. Election timeouts must be at least 10 times the round-trip time so it can account for variance in the network. For example, if the round-trip time between members is 10ms then the election timeout should be at least 100ms.
The upper limit of election timeout is 50000ms (50s), which should only be used when deploying a globally-distributed etcd cluster. A reasonable round-trip time for the continental United States is 130ms, and the time between US and Japan is around 350-400ms. If the network has uneven performance or regular packet delays/loss then it is possible that a couple of retries may be necessary to successfully send a packet. So 5s is a safe upper limit of global round-trip time. As the election timeout should be an order of magnitude bigger than broadcast time, in the case of ~5s for a globally distributed cluster, then 50 seconds becomes a reasonable maximum.
The heartbeat interval and election timeout value should be the same for all members in one cluster. Setting different values for etcd members may disrupt cluster stability.
The default values can be overridden on the command line:
etcd appends all key changes to a log file. This log grows forever and is a complete linear history of every change made to the keys. A complete history works well for lightly used clusters but clusters that are heavily used would carry around a large log.
To avoid having a huge log etcd makes periodic snapshots. These snapshots provide a way for etcd to compact the log by saving the current state of the system and removing old logs.
### Snapshot tuning
Creating snapshots with the V2 backend can be expensive, so snapshots are only created after a given number of changes to etcd. By default, snapshots will be made after every 10,000 changes. If etcd's memory usage and disk usage are too high, try lowering the snapshot threshold by setting the following on the command line:
```sh
# Command line arguments:
$ etcd --snapshot-count=5000
# Environment variables:
$ ETCD_SNAPSHOT_COUNT=5000 etcd
```
## Disk
An etcd cluster is very sensitive to disk latencies. Since etcd must persist proposals to its log, disk activity from other processes may cause long `fsync` latencies. The upshot is etcd may miss heartbeats, causing request timeouts and temporary leader loss. An etcd server can sometimes stably run alongside these processes when given a high disk priority.
On Linux, etcd's disk priority can be configured with `ionice`:
```sh
# best effort, highest priority
$ sudo ionice -c2 -n0 -p `pgrep etcd`
```
## Network
If the etcd leader serves a large number of concurrent client requests, it may delay processing follower peer requests due to network congestion. This manifests as send buffer error messages on the follower nodes:
```
dropped MsgProp to 247ae21ff9436b2d since streamMsg's sending buffer is full
dropped MsgAppResp to 247ae21ff9436b2d since streamMsg's sending buffer is full
```
These errors may be resolved by prioritizing etcd's peer traffic over its client traffic. On Linux, peer traffic can be prioritized by using the traffic control mechanism:
```
tc qdisc add dev eth0 root handle 1: prio bands 3
tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip sport 2380 0xffff flowid 1:1
tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip dport 2380 0xffff flowid 1:1
tc filter add dev eth0 parent 1: protocol ip prio 2 u32 match ip sport 2739 0xffff flowid 1:1
tc filter add dev eth0 parent 1: protocol ip prio 2 u32 match ip dport 2739 0xffff flowid 1:1
In the general case, upgrading from etcd 2.3 to 3.0 can be a zero-downtime, rolling upgrade:
- one by one, stop the etcd v2.3 processes and replace them with etcd v3.0 processes
- after running all v3.0 processes, new features in v3.0 are available to the cluster
Before [starting an upgrade](#upgrade-procedure), read through the rest of this guide to prepare.
### Upgrade checklists
#### Upgrade requirements
To upgrade an existing etcd deployment to 3.0, the running cluster must be 2.3 or greater. If it's before 2.3, please upgrade to [2.3](https://github.com/coreos/etcd/releases/tag/v2.3.8) before upgrading to 3.0.
Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the `etcdctl cluster-health` command before proceeding.
#### Preparation
Before upgrading etcd, always test the services relying on etcd in a staging environment before deploying the upgrade to the production environment.
Before beginning, [backup the etcd data directory](../v2/admin_guide.md#backing-up-the-datastore). Should something go wrong with the upgrade, it is possible to use this backup to [downgrade](#downgrade) back to existing etcd version.
#### Mixed versions
While upgrading, an etcd cluster supports mixed versions of etcd members, and operates with the protocol of the lowest common version. The cluster is only considered upgraded once all of its members are upgraded to version 3.0. Internally, etcd members negotiate with each other to determine the overall cluster version, which controls the reported version and the supported features.
#### Limitations
It might take up to 2 minutes for the newly upgraded member to catch up with the existing cluster when the total data size is larger than 50MB. Check the size of a recent snapshot to estimate the total data size. In other words, it is safest to wait for 2 minutes between upgrading each member.
For a much larger total data size, 100MB or more , this one-time process might take even more time. Administrators of very large etcd clusters of this magnitude can feel free to contact the [etcd team][etcd-contact] before upgrading, and we’ll be happy to provide advice on the procedure.
#### Downgrade
If all members have been upgraded to v3.0, the cluster will be upgraded to v3.0, and downgrade from this completed state is **not possible**. If any single member is still v2.3, however, the cluster and its operations remains “v2.3”, and it is possible from this mixed cluster state to return to using a v2.3 etcd binary on all members.
Please [backup the data directory](../v2/admin_guide.md#backing-up-the-datastore) of all etcd members to make downgrading the cluster possible even after it has been completely upgraded.
### Upgrade procedure
This example details the upgrade of a three-member v2.3 ectd cluster running on a local machine.
#### 1. Check upgrade requirements.
Is the cluster healthy and running v.2.3.x?
```
$ etcdctl cluster-health
member 6e3bd23ae5f1eae0 is healthy: got healthy result from http://localhost:22379
member 924e2e83e93f2560 is healthy: got healthy result from http://localhost:32379
member 8211f1d0f64f3269 is healthy: got healthy result from http://localhost:12379
cluster is healthy
$ curl http://localhost:2379/version
{"etcdserver":"2.3.x","etcdcluster":"2.3.8"}
```
#### 2. Stop the existing etcd process
When each etcd process is stopped, expected errors will be logged by other cluster members. This is normal since a cluster member connection has been (temporarily) broken:
```
2016-06-27 15:21:48.624124 E | rafthttp: failed to dial 8211f1d0f64f3269 on stream Message (dial tcp 127.0.0.1:12380: getsockopt: connection refused)
2016-06-27 15:21:48.624175 I | rafthttp: the connection with 8211f1d0f64f3269 became inactive
```
It’s a good idea at this point to [backup the etcd data directory](../v2/admin_guide.md#backing-up-the-datastore) to provide a downgrade path should any problems occur:
```
$ etcdctl backup \
--data-dir /var/lib/etcd \
--backup-dir /tmp/etcd_backup
```
#### 3. Drop-in etcd v3.0 binary and start the new etcd process
The new v3.0 etcd will publish its information to the cluster:
```
09:58:25.938673 I | etcdserver: published {Name:infra1 ClientURLs:[http://localhost:12379]} to cluster 524400597fb1d5f6
```
Verify that each member, and then the entire cluster, becomes healthy with the new v3.0 etcd binary:
```
$ etcdctl cluster-health
member 6e3bd23ae5f1eae0 is healthy: got healthy result from http://localhost:22379
member 924e2e83e93f2560 is healthy: got healthy result from http://localhost:32379
member 8211f1d0f64f3269 is healthy: got healthy result from http://localhost:12379
cluster is healthy
```
Upgraded members will log warnings like the following until the entire cluster is upgraded. This is expected and will cease after all etcd cluster members are upgraded to v3.0:
```
2016-06-27 15:22:05.679644 W | etcdserver: the local etcd version 2.3.7 is not up-to-date
2016-06-27 15:22:05.679660 W | etcdserver: member 8211f1d0f64f3269 has a higher version 3.0.0
```
#### 4. Repeat step 2 to step 3 for all other members
#### 5. Finish
When all members are upgraded, the cluster will report upgrading to 3.0 successfully:
```
2016-06-27 15:22:19.873751 N | membership: updated the cluster version from 2.3 to 3.0
2016-06-27 15:22:19.914574 I | api: enabled capabilities for version 3.0.0
```
```
$ ETCDCTL_API=3 etcdctl endpoint health
127.0.0.1:12379 is healthy: successfully committed proposal: took = 18.440155ms
127.0.0.1:32379 is healthy: successfully committed proposal: took = 13.651368ms
127.0.0.1:22379 is healthy: successfully committed proposal: took = 18.513301ms
```
## Further considerations
- etcdctl environment variables have been updated. If `ETCDCTL_API=2 etcdctl cluster-health` works properly but `ETCDCTL_API=3 etcdctl endpoints health` responds with `Error: grpc: timed out when dialing`, be sure to use the [new variable names](https://github.com/coreos/etcd/tree/master/etcdctl#etcdctl).
## Known Issues
- etcd < v3.1 does not work properly if built with Go > v1.7. See [Issue 6951](https://github.com/coreos/etcd/issues/6951) for additional information.
- If an error such as `transport: http2Client.notifyError got notified that the client transport was broken unexpected EOF.` shows up in the etcd server logs, be sure etcd is a pre-built release or built with (etcd v3.1+ & go v1.7+) or (etcd <v3.1 & go v1.6.x).
- Adding a v3 node to v2.3 cluster during upgrades is not supported and could trigger panics. See [Issue 7249](https://github.com/coreos/etcd/issues/7429) for additional information. Mixed versions of etcd members are only allowed during v3 migration. Finish upgrades before making any membership changes.
In the general case, upgrading from etcd 3.0 to 3.1 can be a zero-downtime, rolling upgrade:
- one by one, stop the etcd v3.0 processes and replace them with etcd v3.1 processes
- after running all v3.1 processes, new features in v3.1 are available to the cluster
Before [starting an upgrade](#upgrade-procedure), read through the rest of this guide to prepare.
### Upgrade checklists
#### Monitoring
Following metrics from v3.0.x have been deprecated in favor of [go-grpc-prometheus](https://github.com/grpc-ecosystem/go-grpc-prometheus):
-`etcd_grpc_requests_total`
-`etcd_grpc_requests_failed_total`
-`etcd_grpc_active_streams`
-`etcd_grpc_unary_requests_duration_seconds`
#### Upgrade requirements
To upgrade an existing etcd deployment to 3.1, the running cluster must be 3.0 or greater. If it's before 3.0, please [upgrade to 3.0](upgrade_3_0.md) before upgrading to 3.1.
Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the `etcdctl endpoint health` command before proceeding.
#### Preparation
Before upgrading etcd, always test the services relying on etcd in a staging environment before deploying the upgrade to the production environment.
Before beginning, [backup the etcd data](../op-guide/maintenance.md#snapshot-backup). Should something go wrong with the upgrade, it is possible to use this backup to [downgrade](#downgrade) back to existing etcd version. Please note that the `snapshot` command only backs up the v3 data. For v2 data, see [backing up v2 datastore](../v2/admin_guide.md#backing-up-the-datastore).
#### Mixed versions
While upgrading, an etcd cluster supports mixed versions of etcd members, and operates with the protocol of the lowest common version. The cluster is only considered upgraded once all of its members are upgraded to version 3.1. Internally, etcd members negotiate with each other to determine the overall cluster version, which controls the reported version and the supported features.
#### Limitations
Note: If the cluster only has v3 data and no v2 data, it is not subject to this limitation.
If the cluster is serving a v2 data set larger than 50MB, each newly upgraded member may take up to two minutes to catch up with the existing cluster. Check the size of a recent snapshot to estimate the total data size. In other words, it is safest to wait for 2 minutes between upgrading each member.
For a much larger total data size, 100MB or more , this one-time process might take even more time. Administrators of very large etcd clusters of this magnitude can feel free to contact the [etcd team][etcd-contact] before upgrading, and we'll be happy to provide advice on the procedure.
#### Downgrade
If all members have been upgraded to v3.1, the cluster will be upgraded to v3.1, and downgrade from this completed state is **not possible**. If any single member is still v3.0, however, the cluster and its operations remains "v3.0", and it is possible from this mixed cluster state to return to using a v3.0 etcd binary on all members.
Please [backup the data directory](../op-guide/maintenance.md#snapshot-backup) of all etcd members to make downgrading the cluster possible even after it has been completely upgraded.
### Upgrade procedure
This example shows how to upgrade a 3-member v3.0 ectd cluster running on a local machine.
#### 1. Check upgrade requirements
Is the cluster healthy and running v3.0.x?
```
$ ETCDCTL_API=3 etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:2379 is healthy: successfully committed proposal: took = 6.600684ms
localhost:22379 is healthy: successfully committed proposal: took = 8.540064ms
localhost:32379 is healthy: successfully committed proposal: took = 8.763432ms
$ curl http://localhost:2379/version
{"etcdserver":"3.0.16","etcdcluster":"3.0.0"}
```
#### 2. Stop the existing etcd process
When each etcd process is stopped, expected errors will be logged by other cluster members. This is normal since a cluster member connection has been (temporarily) broken:
```
2017-01-17 09:34:18.352662 I | raft: raft.node: 1640829d9eea5cfb elected leader 1640829d9eea5cfb at term 5
2017-01-17 09:34:18.359630 W | etcdserver: failed to reach the peerURL(http://localhost:2380) of member fd32987dcd0511e0 (Get http://localhost:2380/version: dial tcp 127.0.0.1:2380: getsockopt: connection refused)
2017-01-17 09:34:18.359679 W | etcdserver: cannot get the version of member fd32987dcd0511e0 (Get http://localhost:2380/version: dial tcp 127.0.0.1:2380: getsockopt: connection refused)
2017-01-17 09:34:18.548116 W | rafthttp: lost the TCP streaming connection with peer fd32987dcd0511e0 (stream Message writer)
2017-01-17 09:34:19.147816 W | rafthttp: lost the TCP streaming connection with peer fd32987dcd0511e0 (stream MsgApp v2 writer)
2017-01-17 09:34:34.364907 W | etcdserver: failed to reach the peerURL(http://localhost:2380) of member fd32987dcd0511e0 (Get http://localhost:2380/version: dial tcp 127.0.0.1:2380: getsockopt: connection refused)
```
It's a good idea at this point to [backup the etcd data](../op-guide/maintenance.md#snapshot-backup) to provide a downgrade path should any problems occur:
```
$ etcdctl snapshot save backup.db
```
#### 3. Drop-in etcd v3.1 binary and start the new etcd process
The new v3.1 etcd will publish its information to the cluster:
```
2017-01-17 09:36:00.996590 I | etcdserver: published {Name:my-etcd-1 ClientURLs:[http://localhost:2379]} to cluster 46bc3ce73049e678
```
Verify that each member, and then the entire cluster, becomes healthy with the new v3.1 etcd binary:
```
$ ETCDCTL_API=3 /etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:22379 is healthy: successfully committed proposal: took = 5.540129ms
localhost:32379 is healthy: successfully committed proposal: took = 7.321671ms
localhost:2379 is healthy: successfully committed proposal: took = 10.629901ms
```
Upgraded members will log warnings like the following until the entire cluster is upgraded. This is expected and will cease after all etcd cluster members are upgraded to v3.1:
```
2017-01-17 09:36:38.406268 W | etcdserver: the local etcd version 3.0.16 is not up-to-date
2017-01-17 09:36:38.406295 W | etcdserver: member fd32987dcd0511e0 has a higher version 3.1.0
2017-01-17 09:36:42.407695 W | etcdserver: the local etcd version 3.0.16 is not up-to-date
2017-01-17 09:36:42.407730 W | etcdserver: member fd32987dcd0511e0 has a higher version 3.1.0
```
#### 4. Repeat step 2 to step 3 for all other members
#### 5. Finish
When all members are upgraded, the cluster will report upgrading to 3.1 successfully:
```
2017-01-17 09:37:03.100015 I | etcdserver: updating the cluster version from 3.0 to 3.1
2017-01-17 09:37:03.104263 N | etcdserver/membership: updated the cluster version from 3.0 to 3.1
2017-01-17 09:37:03.104374 I | etcdserver/api: enabled capabilities for version 3.1
```
```
$ ETCDCTL_API=3 /etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:2379 is healthy: successfully committed proposal: took = 2.312897ms
localhost:22379 is healthy: successfully committed proposal: took = 2.553476ms
localhost:32379 is healthy: successfully committed proposal: took = 2.516902ms
In the general case, upgrading from etcd 3.1 to 3.2 can be a zero-downtime, rolling upgrade:
- one by one, stop the etcd v3.1 processes and replace them with etcd v3.2 processes
- after running all v3.2 processes, new features in v3.2 are available to the cluster
Before [starting an upgrade](#upgrade-procedure), read through the rest of this guide to prepare.
### Client upgrade checklists
3.2 introduces two breaking changes.
Previously, `clientv3.Lease.TimeToLive` API returned `lease.ErrLeaseNotFound` on non-existent lease ID. 3.2 instead returns TTL=-1 in its response and no error (see [#7305](https://github.com/coreos/etcd/pull/7305)).
Before
```go
// when leaseID does not exist
resp,err:=TimeToLive(ctx,leaseID)
resp==nil
err==lease.ErrLeaseNotFound
```
After
```go
// when leaseID does not exist
resp,err:=TimeToLive(ctx,leaseID)
resp.TTL==-1
err==nil
```
`clientv3.NewFromConfigFile` is moved to `yaml.NewConfig`.
>=3.2.10 upgrades `grpc/grpc-go` to >=v1.7.x from v1.2.1, which introduces some breaking changes.
Previously, `grpc.ErrClientConnTimeout` error is returned on client dial time-outs. >=3.2.10 instead returns `context.DeadlineExceeded` (see [#8504](https://github.com/coreos/etcd/issues/8504)).
Before
```go
// expect dial time-out on ipv4 blackhole
_,err:=clientv3.New(clientv3.Config{
Endpoints:[]string{"http://254.0.0.1:12345"},
DialTimeout:2*time.Second
})
iferr==grpc.ErrClientConnTimeout{
// handle errors
}
```
After
```go
_,err:=clientv3.New(clientv3.Config{
Endpoints:[]string{"http://254.0.0.1:12345"},
DialTimeout:2*time.Second
})
iferr==context.DeadlineExceeded{
// handle errors
}
```
### Server upgrade checklists
#### Upgrade requirements
To upgrade an existing etcd deployment to 3.2, the running cluster must be 3.1 or greater. If it's before 3.1, please [upgrade to 3.1](upgrade_3_1.md) before upgrading to 3.2.
Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the `etcdctl endpoint health` command before proceeding.
#### Preparation
Before upgrading etcd, always test the services relying on etcd in a staging environment before deploying the upgrade to the production environment.
Before beginning, [backup the etcd data](../op-guide/maintenance.md#snapshot-backup). Should something go wrong with the upgrade, it is possible to use this backup to [downgrade](#downgrade) back to existing etcd version. Please note that the `snapshot` command only backs up the v3 data. For v2 data, see [backing up v2 datastore](../v2/admin_guide.md#backing-up-the-datastore).
#### Mixed versions
While upgrading, an etcd cluster supports mixed versions of etcd members, and operates with the protocol of the lowest common version. The cluster is only considered upgraded once all of its members are upgraded to version 3.2. Internally, etcd members negotiate with each other to determine the overall cluster version, which controls the reported version and the supported features.
#### Limitations
Note: If the cluster only has v3 data and no v2 data, it is not subject to this limitation.
If the cluster is serving a v2 data set larger than 50MB, each newly upgraded member may take up to two minutes to catch up with the existing cluster. Check the size of a recent snapshot to estimate the total data size. In other words, it is safest to wait for 2 minutes between upgrading each member.
For a much larger total data size, 100MB or more , this one-time process might take even more time. Administrators of very large etcd clusters of this magnitude can feel free to contact the [etcd team][etcd-contact] before upgrading, and we'll be happy to provide advice on the procedure.
#### Downgrade
If all members have been upgraded to v3.2, the cluster will be upgraded to v3.2, and downgrade from this completed state is **not possible**. If any single member is still v3.1, however, the cluster and its operations remains "v3.1", and it is possible from this mixed cluster state to return to using a v3.1 etcd binary on all members.
Please [backup the data directory](../op-guide/maintenance.md#snapshot-backup) of all etcd members to make downgrading the cluster possible even after it has been completely upgraded.
### Upgrade procedure
This example shows how to upgrade a 3-member v3.1 ectd cluster running on a local machine.
#### 1. Check upgrade requirements
Is the cluster healthy and running v3.1.x?
```
$ ETCDCTL_API=3 etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:2379 is healthy: successfully committed proposal: took = 6.600684ms
localhost:22379 is healthy: successfully committed proposal: took = 8.540064ms
localhost:32379 is healthy: successfully committed proposal: took = 8.763432ms
$ curl http://localhost:2379/version
{"etcdserver":"3.1.7","etcdcluster":"3.1.0"}
```
#### 2. Stop the existing etcd process
When each etcd process is stopped, expected errors will be logged by other cluster members. This is normal since a cluster member connection has been (temporarily) broken:
```
2017-04-27 14:13:31.491746 I | raft: c89feb932daef420 [term 3] received MsgTimeoutNow from 6d4f535bae3ab960 and starts an election to get leadership.
2017-04-27 14:13:31.491769 I | raft: c89feb932daef420 became candidate at term 4
2017-04-27 14:13:31.491788 I | raft: c89feb932daef420 received MsgVoteResp from c89feb932daef420 at term 4
2017-04-27 14:13:31.491797 I | raft: c89feb932daef420 [logterm: 3, index: 9] sent MsgVote request to 6d4f535bae3ab960 at term 4
2017-04-27 14:13:31.491805 I | raft: c89feb932daef420 [logterm: 3, index: 9] sent MsgVote request to 9eda174c7df8a033 at term 4
2017-04-27 14:13:31.491815 I | raft: raft.node: c89feb932daef420 lost leader 6d4f535bae3ab960 at term 4
2017-04-27 14:13:31.524084 I | raft: c89feb932daef420 received MsgVoteResp from 6d4f535bae3ab960 at term 4
2017-04-27 14:13:31.524108 I | raft: c89feb932daef420 [quorum:2] has received 2 MsgVoteResp votes and 0 vote rejections
2017-04-27 14:13:31.524123 I | raft: c89feb932daef420 became leader at term 4
2017-04-27 14:13:31.524136 I | raft: raft.node: c89feb932daef420 elected leader c89feb932daef420 at term 4
2017-04-27 14:13:31.592650 W | rafthttp: lost the TCP streaming connection with peer 6d4f535bae3ab960 (stream MsgApp v2 reader)
2017-04-27 14:13:31.592825 W | rafthttp: lost the TCP streaming connection with peer 6d4f535bae3ab960 (stream Message reader)
2017-04-27 14:13:31.693275 E | rafthttp: failed to dial 6d4f535bae3ab960 on stream Message (dial tcp [::1]:2380: getsockopt: connection refused)
2017-04-27 14:13:31.693289 I | rafthttp: peer 6d4f535bae3ab960 became inactive
2017-04-27 14:13:31.936678 W | rafthttp: lost the TCP streaming connection with peer 6d4f535bae3ab960 (stream Message writer)
```
It's a good idea at this point to [backup the etcd data](../op-guide/maintenance.md#snapshot-backup) to provide a downgrade path should any problems occur:
```
$ etcdctl snapshot save backup.db
```
#### 3. Drop-in etcd v3.2 binary and start the new etcd process
The new v3.2 etcd will publish its information to the cluster:
```
2017-04-27 14:14:25.363225 I | etcdserver: published {Name:s1 ClientURLs:[http://localhost:2379]} to cluster a9ededbffcb1b1f1
```
Verify that each member, and then the entire cluster, becomes healthy with the new v3.2 etcd binary:
```
$ ETCDCTL_API=3 /etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:22379 is healthy: successfully committed proposal: took = 5.540129ms
localhost:32379 is healthy: successfully committed proposal: took = 7.321771ms
localhost:2379 is healthy: successfully committed proposal: took = 10.629901ms
```
Upgraded members will log warnings like the following until the entire cluster is upgraded. This is expected and will cease after all etcd cluster members are upgraded to v3.2:
```
2017-04-27 14:15:17.071804 W | etcdserver: member c89feb932daef420 has a higher version 3.2.0
2017-04-27 14:15:21.073110 W | etcdserver: the local etcd version 3.1.7 is not up-to-date
2017-04-27 14:15:21.073142 W | etcdserver: member 6d4f535bae3ab960 has a higher version 3.2.0
2017-04-27 14:15:21.073157 W | etcdserver: the local etcd version 3.1.7 is not up-to-date
2017-04-27 14:15:21.073164 W | etcdserver: member c89feb932daef420 has a higher version 3.2.0
```
#### 4. Repeat step 2 to step 3 for all other members
#### 5. Finish
When all members are upgraded, the cluster will report upgrading to 3.2 successfully:
```
2017-04-27 14:15:54.536901 N | etcdserver/membership: updated the cluster version from 3.1 to 3.2
2017-04-27 14:15:54.537035 I | etcdserver/api: enabled capabilities for version 3.2
```
```
$ ETCDCTL_API=3 /etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:2379 is healthy: successfully committed proposal: took = 2.312897ms
localhost:22379 is healthy: successfully committed proposal: took = 2.553476ms
localhost:32379 is healthy: successfully committed proposal: took = 2.517902ms
In the general case, upgrading from etcd 3.2 to 3.3 can be a zero-downtime, rolling upgrade:
- one by one, stop the etcd v3.2 processes and replace them with etcd v3.3 processes
- after running all v3.3 processes, new features in v3.3 are available to the cluster
Before [starting an upgrade](#upgrade-procedure), read through the rest of this guide to prepare.
### Client upgrade checklists
3.3 introduces breaking changes (TODO: update this before 3.3 release).
Previously, `grpc.ErrClientConnTimeout` error is returned on client dial time-outs. 3.3 instead returns `context.DeadlineExceeded` (see [#8504](https://github.com/coreos/etcd/issues/8504)).
Before
```go
// expect dial time-out on ipv4 blackhole
_,err:=clientv3.New(clientv3.Config{
Endpoints:[]string{"http://254.0.0.1:12345"},
DialTimeout:2*time.Second
})
iferr==grpc.ErrClientConnTimeout{
// handle errors
}
```
After
```go
_,err:=clientv3.New(clientv3.Config{
Endpoints:[]string{"http://254.0.0.1:12345"},
DialTimeout:2*time.Second
})
iferr==context.DeadlineExceeded{
// handle errors
}
```
### Server upgrade checklists
#### Upgrade requirements
To upgrade an existing etcd deployment to 3.3, the running cluster must be 3.2 or greater. If it's before 3.2, please [upgrade to 3.2](upgrade_3_2.md) before upgrading to 3.3.
Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the `etcdctl endpoint health` command before proceeding.
#### Preparation
Before upgrading etcd, always test the services relying on etcd in a staging environment before deploying the upgrade to the production environment.
Before beginning, [backup the etcd data](../op-guide/maintenance.md#snapshot-backup). Should something go wrong with the upgrade, it is possible to use this backup to [downgrade](#downgrade) back to existing etcd version. Please note that the `snapshot` command only backs up the v3 data. For v2 data, see [backing up v2 datastore](../v2/admin_guide.md#backing-up-the-datastore).
#### Mixed versions
While upgrading, an etcd cluster supports mixed versions of etcd members, and operates with the protocol of the lowest common version. The cluster is only considered upgraded once all of its members are upgraded to version 3.3. Internally, etcd members negotiate with each other to determine the overall cluster version, which controls the reported version and the supported features.
#### Limitations
Note: If the cluster only has v3 data and no v2 data, it is not subject to this limitation.
If the cluster is serving a v2 data set larger than 50MB, each newly upgraded member may take up to two minutes to catch up with the existing cluster. Check the size of a recent snapshot to estimate the total data size. In other words, it is safest to wait for 2 minutes between upgrading each member.
For a much larger total data size, 100MB or more , this one-time process might take even more time. Administrators of very large etcd clusters of this magnitude can feel free to contact the [etcd team][etcd-contact] before upgrading, and we'll be happy to provide advice on the procedure.
#### Downgrade
If all members have been upgraded to v3.3, the cluster will be upgraded to v3.3, and downgrade from this completed state is **not possible**. If any single member is still v3.2, however, the cluster and its operations remains "v3.2", and it is possible from this mixed cluster state to return to using a v3.2 etcd binary on all members.
Please [backup the data directory](../op-guide/maintenance.md#snapshot-backup) of all etcd members to make downgrading the cluster possible even after it has been completely upgraded.
### Upgrade procedure
This example shows how to upgrade a 3-member v3.2 ectd cluster running on a local machine.
#### 1. Check upgrade requirements
Is the cluster healthy and running v3.2.x?
```
$ ETCDCTL_API=3 etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:2379 is healthy: successfully committed proposal: took = 6.600684ms
localhost:22379 is healthy: successfully committed proposal: took = 8.540064ms
localhost:32379 is healthy: successfully committed proposal: took = 8.763432ms
$ curl http://localhost:2379/version
{"etcdserver":"3.2.7","etcdcluster":"3.2.0"}
```
#### 2. Stop the existing etcd process
When each etcd process is stopped, expected errors will be logged by other cluster members. This is normal since a cluster member connection has been (temporarily) broken:
```
14:13:31.491746 I | raft: c89feb932daef420 [term 3] received MsgTimeoutNow from 6d4f535bae3ab960 and starts an election to get leadership.
14:13:31.491769 I | raft: c89feb932daef420 became candidate at term 4
14:13:31.491788 I | raft: c89feb932daef420 received MsgVoteResp from c89feb932daef420 at term 4
14:13:31.491797 I | raft: c89feb932daef420 [logterm: 3, index: 9] sent MsgVote request to 6d4f535bae3ab960 at term 4
14:13:31.491805 I | raft: c89feb932daef420 [logterm: 3, index: 9] sent MsgVote request to 9eda174c7df8a033 at term 4
14:13:31.491815 I | raft: raft.node: c89feb932daef420 lost leader 6d4f535bae3ab960 at term 4
14:13:31.524084 I | raft: c89feb932daef420 received MsgVoteResp from 6d4f535bae3ab960 at term 4
14:13:31.524108 I | raft: c89feb932daef420 [quorum:2] has received 2 MsgVoteResp votes and 0 vote rejections
14:13:31.524123 I | raft: c89feb932daef420 became leader at term 4
14:13:31.524136 I | raft: raft.node: c89feb932daef420 elected leader c89feb932daef420 at term 4
14:13:31.592650 W | rafthttp: lost the TCP streaming connection with peer 6d4f535bae3ab960 (stream MsgApp v2 reader)
14:13:31.592825 W | rafthttp: lost the TCP streaming connection with peer 6d4f535bae3ab960 (stream Message reader)
14:13:31.693275 E | rafthttp: failed to dial 6d4f535bae3ab960 on stream Message (dial tcp [::1]:2380: getsockopt: connection refused)
14:13:31.693289 I | rafthttp: peer 6d4f535bae3ab960 became inactive
14:13:31.936678 W | rafthttp: lost the TCP streaming connection with peer 6d4f535bae3ab960 (stream Message writer)
```
It's a good idea at this point to [backup the etcd data](../op-guide/maintenance.md#snapshot-backup) to provide a downgrade path should any problems occur:
```
$ etcdctl snapshot save backup.db
```
#### 3. Drop-in etcd v3.3 binary and start the new etcd process
The new v3.3 etcd will publish its information to the cluster:
```
14:14:25.363225 I | etcdserver: published {Name:s1 ClientURLs:[http://localhost:2379]} to cluster a9ededbffcb1b1f1
```
Verify that each member, and then the entire cluster, becomes healthy with the new v3.3 etcd binary:
```
$ ETCDCTL_API=3 /etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:22379 is healthy: successfully committed proposal: took = 5.540129ms
localhost:32379 is healthy: successfully committed proposal: took = 7.321771ms
localhost:2379 is healthy: successfully committed proposal: took = 10.629901ms
```
Upgraded members will log warnings like the following until the entire cluster is upgraded. This is expected and will cease after all etcd cluster members are upgraded to v3.3:
```
14:15:17.071804 W | etcdserver: member c89feb932daef420 has a higher version 3.3.0
14:15:21.073110 W | etcdserver: the local etcd version 3.2.7 is not up-to-date
14:15:21.073142 W | etcdserver: member 6d4f535bae3ab960 has a higher version 3.3.0
14:15:21.073157 W | etcdserver: the local etcd version 3.2.7 is not up-to-date
14:15:21.073164 W | etcdserver: member c89feb932daef420 has a higher version 3.3.0
```
#### 4. Repeat step 2 to step 3 for all other members
#### 5. Finish
When all members are upgraded, the cluster will report upgrading to 3.3 successfully:
```
14:15:54.536901 N | etcdserver/membership: updated the cluster version from 3.2 to 3.3
14:15:54.537035 I | etcdserver/api: enabled capabilities for version 3.3
```
```
$ ETCDCTL_API=3 /etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
localhost:2379 is healthy: successfully committed proposal: took = 2.312897ms
localhost:22379 is healthy: successfully committed proposal: took = 2.553476ms
localhost:32379 is healthy: successfully committed proposal: took = 2.517902ms
This section contains documents specific to upgrading etcd clusters and applications.
## Moving from etcd API v2 to API v3
* [Migrate applications from using API v2 to API v3][migrate-apps]
## Upgrading an etcd v3.x cluster
* [Upgrade etcd from 3.0 to 3.1][upgrade-3-1]
* [Upgrade etcd from 3.1 to 3.2][upgrade-3-2]
## Upgrading from etcd v2.3
* [Upgrade a v2.3 cluster to v3.0][upgrade-cluster]
[migrate-apps]: ../op-guide/v2-migration.md
[upgrade-cluster]: upgrade_3_0.md
[upgrade-3-1]: upgrade_3_1.md
[upgrade-3-2]: upgrade_3_2.md
Some files were not shown because too many files have changed in this diff
Show More
Reference in New Issue
Block a user
Blocking a user prevents them from interacting with repositories, such as opening or commenting on pull requests or issues. Learn more about blocking a user.
