fix(grpcproxy): support grpc context propagation in grpc proxy;fix th…

…e problem that watch exits when recvLoop exits but sendLoop still running

server/etcdmain/grpc_proxy.go

@@ -19,6 +19,7 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"fmt"
+	"google.golang.org/grpc/metadata"
 	"io"
 	"log"
 	"math"
@@ -422,6 +423,20 @@ func mustListenCMux(lg *zap.Logger, tlsinfo *transport.TLSInfo) cmux.CMux {
 	return cmux.New(l)
 }
 
+func contextPropagationUnaryServerInterceptor() grpc.UnaryServerInterceptor {
+	return func(
+		ctx context.Context,
+		req interface{},
+		info *grpc.UnaryServerInfo,
+		handler grpc.UnaryHandler,
+	) (interface{}, error) {
+		if md, ok := metadata.FromIncomingContext(ctx); ok {
+			ctx = metadata.NewOutgoingContext(ctx, md)
+		}
+		return handler(ctx, req)
+	}
+}
+
 func newGRPCProxyServer(lg *zap.Logger, client *clientv3.Client) *grpc.Server {
 	if grpcProxyEnableOrdering {
 		vf := ordering.NewOrderViolationSwitchEndpointClosure(client)
@@ -467,6 +482,7 @@ func newGRPCProxyServer(lg *zap.Logger, client *clientv3.Client) *grpc.Server {
 	}
 	grpcChainUnaryList := []grpc.UnaryServerInterceptor{
 		grpc_prometheus.UnaryServerInterceptor,
+		contextPropagationUnaryServerInterceptor(),
 	}
 	if grpcProxyEnableLogging {
 		grpcChainStreamList = append(grpcChainStreamList,

server/proxy/grpcproxy/watch.go

@@ -123,7 +123,8 @@ func (wp *watchProxy) Watch(stream pb.Watch_WatchServer) (err error) {
 
 	// post to stopc => terminate server stream; can't use a waitgroup
 	// since all goroutines will only terminate after Watch() exits.
-	stopc := make(chan struct{}, 3)
+	stopc := make(chan struct{}, 2)
+	leaderc := make(chan struct{}, 1)
 	go func() {
 		defer func() { stopc <- struct{}{} }()
 		wps.recvLoop()
@@ -134,15 +135,15 @@ func (wp *watchProxy) Watch(stream pb.Watch_WatchServer) (err error) {
 	}()
 	// tear down watch if leader goes down or entire watch proxy is terminated
 	go func() {
-		defer func() { stopc <- struct{}{} }()
+		defer func() { leaderc <- struct{}{} }()
 		select {
 		case <-lostLeaderC:
 		case <-ctx.Done():
 		case <-wp.ctx.Done():
 		}
 	}()
 
-	<-stopc
+	<-leaderc
 	cancel()
 
 	// recv/send may only shutdown after function exits;