128 lines
3.3 KiB
Go
128 lines
3.3 KiB
Go
// Copyright 2016 CoreOS, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package command
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import (
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"fmt"
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"io"
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"os"
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"github.com/coreos/etcd/clientv3"
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"github.com/coreos/etcd/clientv3/mirror"
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"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
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"github.com/spf13/cobra"
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"golang.org/x/net/context"
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)
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// NewSnapshotCommand returns the cobra command for "snapshot".
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func NewSnapshotCommand() *cobra.Command {
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return &cobra.Command{
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Use: "snapshot [filename]",
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Short: "Snapshot streams a point-in-time snapshot of the store",
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Run: snapshotCommandFunc,
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}
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}
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// snapshotCommandFunc watches for the length of the entire store and records
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// to a file.
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func snapshotCommandFunc(cmd *cobra.Command, args []string) {
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switch {
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case len(args) == 0:
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snapshotToStdout(mustClientFromCmd(cmd))
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case len(args) == 1:
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snapshotToFile(mustClientFromCmd(cmd), args[0])
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default:
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err := fmt.Errorf("snapshot takes at most one argument")
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ExitWithError(ExitBadArgs, err)
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}
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}
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// snapshotToStdout streams a snapshot over stdout
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func snapshotToStdout(c *clientv3.Client) {
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// must explicitly fetch first revision since no retry on stdout
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wr := <-c.Watch(context.TODO(), "", clientv3.WithPrefix(), clientv3.WithRev(1))
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if wr.Err() == nil {
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wr.CompactRevision = 1
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}
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if rev := snapshot(os.Stdout, c, wr.CompactRevision+1); rev != 0 {
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err := fmt.Errorf("snapshot interrupted by compaction %v", rev)
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ExitWithError(ExitInterrupted, err)
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}
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os.Stdout.Sync()
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}
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// snapshotToFile atomically writes a snapshot to a file
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func snapshotToFile(c *clientv3.Client, path string) {
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partpath := path + ".part"
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f, err := os.Create(partpath)
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defer f.Close()
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if err != nil {
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exiterr := fmt.Errorf("could not open %s (%v)", partpath, err)
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ExitWithError(ExitBadArgs, exiterr)
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}
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rev := int64(1)
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for rev != 0 {
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f.Seek(0, 0)
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f.Truncate(0)
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rev = snapshot(f, c, rev)
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}
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f.Sync()
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if err := os.Rename(partpath, path); err != nil {
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exiterr := fmt.Errorf("could not rename %s to %s (%v)", partpath, path, err)
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ExitWithError(ExitIO, exiterr)
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}
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}
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// snapshot reads all of a watcher; returns compaction revision if incomplete
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// TODO: stabilize snapshot format
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func snapshot(w io.Writer, c *clientv3.Client, rev int64) int64 {
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s := mirror.NewSyncer(c, "", rev)
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rc, errc := s.SyncBase(context.TODO())
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for r := range rc {
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for _, kv := range r.Kvs {
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fmt.Fprintln(w, kv)
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}
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}
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err := <-errc
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if err != nil {
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if err == rpctypes.ErrCompacted {
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// will get correct compact revision on retry
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return rev + 1
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}
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// failed for some unknown reason, retry on same revision
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return rev
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}
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wc := s.SyncUpdates(context.TODO())
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for wr := range wc {
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if wr.Err() != nil {
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return wr.CompactRevision
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}
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for _, ev := range wr.Events {
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fmt.Fprintln(w, ev)
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}
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rev := wr.Events[len(wr.Events)-1].Kv.ModRevision
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if rev >= wr.Header.Revision {
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break
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}
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}
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return 0
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}
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