*: etcd member rejects unary call with leader requirement when it does not have leader

etcdserver/api/v3rpc/grpc.go

@@ -28,7 +28,7 @@ func Server(s *etcdserver.EtcdServer, tls *tls.Config) *grpc.Server {
 	if tls != nil {
 		opts = append(opts, grpc.Creds(credentials.NewTLS(tls)))
 	}
-	opts = append(opts, grpc.UnaryInterceptor(metricsUnaryInterceptor))
+	opts = append(opts, grpc.UnaryInterceptor(newUnaryInterceptor(s)))
 	opts = append(opts, grpc.StreamInterceptor(metricsStreamInterceptor))
 
 	grpcServer := grpc.NewServer(opts...)

etcdserver/api/v3rpc/interceptor.go

@@ -0,0 +1,77 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package v3rpc
+
+import (
+	"strings"
+	"time"
+
+	"github.com/coreos/etcd/etcdserver"
+	"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
+	"github.com/coreos/etcd/pkg/types"
+	"github.com/coreos/etcd/raft"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+)
+
+func newUnaryInterceptor(s *etcdserver.EtcdServer) grpc.UnaryServerInterceptor {
+	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
+		md, ok := metadata.FromContext(ctx)
+		if ok {
+			if ks := md[rpctypes.MetadataRequireLeaderKey]; len(ks) > 0 && ks[0] == rpctypes.MetadataHasLeader {
+				if s.Leader() == types.ID(raft.None) {
+					return nil, rpctypes.ErrGRPCNoLeader
+				}
+			}
+		}
+		return metricsUnaryInterceptor(ctx, req, info, handler)
+	}
+}
+
+func metricsUnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
+	service, method := splitMethodName(info.FullMethod)
+	receivedCounter.WithLabelValues(service, method).Inc()
+
+	start := time.Now()
+	resp, err = handler(ctx, req)
+	if err != nil {
+		failedCounter.WithLabelValues(service, method, grpc.Code(err).String()).Inc()
+	}
+	handlingDuration.WithLabelValues(service, method).Observe(time.Since(start).Seconds())
+
+	return resp, err
+}
+
+func metricsStreamInterceptor(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+	service, method := splitMethodName(info.FullMethod)
+	receivedCounter.WithLabelValues(service, method).Inc()
+
+	err := handler(srv, ss)
+	if err != nil {
+		failedCounter.WithLabelValues(service, method, grpc.Code(err).String()).Inc()
+	}
+
+	return err
+}
+
+func splitMethodName(fullMethodName string) (string, string) {
+	fullMethodName = strings.TrimPrefix(fullMethodName, "/") // remove leading slash
+	if i := strings.Index(fullMethodName, "/"); i >= 0 {
+		return fullMethodName[:i], fullMethodName[i+1:]
+	}
+	return "unknown", "unknown"
+}

etcdserver/api/v3rpc/metrics.go

@@ -14,15 +14,7 @@
 
 package v3rpc
 
-import (
+import "github.com/prometheus/client_golang/prometheus"
-	"strings"
-	"time"
-
-	"github.com/prometheus/client_golang/prometheus"
-
-	"golang.org/x/net/context"
-	"google.golang.org/grpc"
-)
 
 var (
 	receivedCounter = prometheus.NewCounterVec(
@@ -51,40 +43,6 @@ var (
 		}, []string{"grpc_service", "grpc_method"})
 )
 
-func metricsUnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
-	service, method := splitMethodName(info.FullMethod)
-	receivedCounter.WithLabelValues(service, method).Inc()
-
-	start := time.Now()
-	resp, err = handler(ctx, req)
-	if err != nil {
-		failedCounter.WithLabelValues(service, method, grpc.Code(err).String()).Inc()
-	}
-	handlingDuration.WithLabelValues(service, method).Observe(time.Since(start).Seconds())
-
-	return resp, err
-}
-
-func metricsStreamInterceptor(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
-	service, method := splitMethodName(info.FullMethod)
-	receivedCounter.WithLabelValues(service, method).Inc()
-
-	err := handler(srv, ss)
-	if err != nil {
-		failedCounter.WithLabelValues(service, method, grpc.Code(err).String()).Inc()
-	}
-
-	return err
-}
-
-func splitMethodName(fullMethodName string) (string, string) {
-	fullMethodName = strings.TrimPrefix(fullMethodName, "/") // remove leading slash
-	if i := strings.Index(fullMethodName, "/"); i >= 0 {
-		return fullMethodName[:i], fullMethodName[i+1:]
-	}
-	return "unknown", "unknown"
-}
-
 func init() {
 	prometheus.MustRegister(receivedCounter)
 	prometheus.MustRegister(failedCounter)

etcdserver/api/v3rpc/rpctypes/error.go

@@ -44,6 +44,8 @@ var (
 	ErrGRPCRoleNotFound     = grpc.Errorf(codes.FailedPrecondition, "etcdserver: role name not found")
 	ErrGRPCAuthFailed       = grpc.Errorf(codes.InvalidArgument, "etcdserver: authentication failed, invalid user ID or password")
 
+	ErrGRPCNoLeader = grpc.Errorf(codes.Unavailable, "etcdserver: no leader")
+
 	errStringToError = map[string]error{
 		grpc.ErrorDesc(ErrGRPCEmptyKey):     ErrGRPCEmptyKey,
 		grpc.ErrorDesc(ErrGRPCTooManyOps):   ErrGRPCTooManyOps,
@@ -67,6 +69,8 @@ var (
 		grpc.ErrorDesc(ErrGRPCRoleAlreadyExist): ErrGRPCRoleAlreadyExist,
 		grpc.ErrorDesc(ErrGRPCRoleNotFound):     ErrGRPCRoleNotFound,
 		grpc.ErrorDesc(ErrGRPCAuthFailed):       ErrGRPCAuthFailed,
+
+		grpc.ErrorDesc(ErrGRPCNoLeader): ErrGRPCNoLeader,
 	}
 
 	// client-side error
@@ -92,6 +96,8 @@ var (
 	ErrRoleAlreadyExist = Error(ErrGRPCRoleAlreadyExist)
 	ErrRoleNotFound     = Error(ErrGRPCRoleNotFound)
 	ErrAuthFailed       = Error(ErrGRPCAuthFailed)
+
+	ErrNoLeader = Error(ErrGRPCNoLeader)
 )
 
 // EtcdError defines gRPC server errors.

etcdserver/api/v3rpc/rpctypes/md.go

@@ -0,0 +1,20 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rpctypes
+
+var (
+	MetadataRequireLeaderKey = "hasleader"
+	MetadataHasLeader        = "true"
+)

integration/v3_grpc_test.go

@@ -27,6 +27,7 @@ import (
 	"github.com/coreos/etcd/pkg/testutil"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
 )
 
 // TestV3PutOverwrite puts a key with the v3 api to a random cluster member,
@@ -976,3 +977,30 @@ func TestTLSGRPCAcceptSecureAll(t *testing.T) {
 		t.Fatalf("unexpected error on put over tls (%v)", err)
 	}
 }
+
+func TestGRPCRequireLeader(t *testing.T) {
+	defer testutil.AfterTest(t)
+
+	cfg := ClusterConfig{Size: 3}
+	clus := newClusterV3NoClients(t, &cfg)
+	defer clus.Terminate(t)
+
+	clus.Members[1].Stop(t)
+	clus.Members[2].Stop(t)
+
+	client, err := NewClientV3(clus.Members[0])
+	if err != nil {
+		t.Fatalf("expected tls client (%v)", err)
+	}
+	defer client.Close()
+
+	// wait for election timeout, then member[0] will not have a leader.
+	time.Sleep(time.Duration(3*electionTicks) * tickDuration)
+
+	md := metadata.Pairs(rpctypes.MetadataRequireLeaderKey, rpctypes.MetadataHasLeader)
+	ctx := metadata.NewContext(context.Background(), md)
+	reqput := &pb.PutRequest{Key: []byte("foo"), Value: []byte("bar")}
+	if _, err := toGRPC(client).KV.Put(ctx, reqput); grpc.ErrorDesc(err) != rpctypes.ErrNoLeader.Error() {
+		t.Errorf("err = %v, want %v", err, rpctypes.ErrNoLeader)
+	}
+}