mcs: tso service should not forward again (tikv#7348)

ref tikv#5836

Signed-off-by: Ryan Leung <rleungx@gmail.com>

Co-authored-by: ti-chi-bot[bot] <108142056+ti-chi-bot[bot]@users.noreply.github.com>

pkg/mcs/tso/server/grpc_service.go

@@ -28,8 +28,6 @@ import (
 	bs "github.com/tikv/pd/pkg/basicserver"
 	"github.com/tikv/pd/pkg/mcs/registry"
 	"github.com/tikv/pd/pkg/utils/apiutil"
-	"github.com/tikv/pd/pkg/utils/grpcutil"
-	"github.com/tikv/pd/pkg/utils/tsoutil"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
@@ -88,21 +86,9 @@ func (s *Service) RegisterRESTHandler(userDefineHandlers map[string]http.Handler
 
 // Tso returns a stream of timestamps
 func (s *Service) Tso(stream tsopb.TSO_TsoServer) error {
-	var (
-		doneCh chan struct{}
-		errCh  chan error
-	)
 	ctx, cancel := context.WithCancel(stream.Context())
 	defer cancel()
 	for {
-		// Prevent unnecessary performance overhead of the channel.
-		if errCh != nil {
-			select {
-			case err := <-errCh:
-				return errors.WithStack(err)
-			default:
-			}
-		}
 		request, err := stream.Recv()
 		if err == io.EOF {
 			return nil
@@ -111,26 +97,6 @@ func (s *Service) Tso(stream tsopb.TSO_TsoServer) error {
 			return errors.WithStack(err)
 		}
 
-		streamCtx := stream.Context()
-		forwardedHost := grpcutil.GetForwardedHost(streamCtx)
-		if !s.IsLocalRequest(forwardedHost) {
-			clientConn, err := s.GetDelegateClient(s.Context(), s.GetTLSConfig(), forwardedHost)
-			if err != nil {
-				return errors.WithStack(err)
-			}
-
-			if errCh == nil {
-				doneCh = make(chan struct{})
-				defer close(doneCh)
-				errCh = make(chan error)
-			}
-
-			tsoProtoFactory := s.tsoProtoFactory
-			tsoRequest := tsoutil.NewTSOProtoRequest(forwardedHost, clientConn, request, stream)
-			s.tsoDispatcher.DispatchRequest(ctx, tsoRequest, tsoProtoFactory, doneCh, errCh)
-			continue
-		}
-
 		start := time.Now()
 		// TSO uses leader lease to determine validity. No need to check leader here.
 		if s.IsClosed() {

pkg/mcs/tso/server/server.go

@@ -78,9 +78,6 @@ type Server struct {
 	service              *Service
 	keyspaceGroupManager *tso.KeyspaceGroupManager
 
-	// tsoDispatcher is used to dispatch the TSO requests to
-	// the corresponding forwarding TSO channels.
-	tsoDispatcher *tsoutil.TSODispatcher
 	// tsoProtoFactory is the abstract factory for creating tso
 	// related data structures defined in the tso grpc protocol
 	tsoProtoFactory *tsoutil.TSOProtoFactory