Merge pull request grpc#863 from menghanl/setTrailer

Allow multiple setTrailer

server.go

@@ -886,8 +886,8 @@ func SendHeader(ctx context.Context, md metadata.MD) error {
 }
 
 // SetTrailer sets the trailer metadata that will be sent when an RPC returns.
-// It may be called at most once from a unary RPC handler. The ctx is the RPC
-// handler's Context or one derived from it.
+// When called more than once, all the provided metadata will be merged.
+// The ctx is the RPC handler's Context or one derived from it.
 func SetTrailer(ctx context.Context, md metadata.MD) error {
 	if md.Len() == 0 {
 		return nil

stream.go

@@ -414,8 +414,8 @@ type ServerStream interface {
 	// after SendProto. It fails if called multiple times or if
 	// called after SendProto.
 	SendHeader(metadata.MD) error
-	// SetTrailer sets the trailer metadata which will be sent with the
-	// RPC status.
+	// SetTrailer sets the trailer metadata which will be sent with the RPC status.
+	// When called more than once, all the provided metadata will be merged.
 	SetTrailer(metadata.MD)
 	Stream
 }

test/end2end_test.go

@@ -79,6 +79,10 @@ var (
 		"tkey1": []string{"trailerValue1"},
 		"tkey2": []string{"trailerValue2"},
 	}
+	testTrailerMetadata2 = metadata.MD{
+		"tkey1": []string{"trailerValue12"},
+		"tkey2": []string{"trailerValue22"},
+	}
 	// capital "Key" is illegal in HTTP/2.
 	malformedHTTP2Metadata = metadata.MD{
 		"Key": []string{"foo"},
@@ -89,8 +93,9 @@ var (
 var raceMode bool // set by race_test.go in race mode
 
 type testServer struct {
-	security  string // indicate the authentication protocol used by this server.
-	earlyFail bool   // whether to error out the execution of a service handler prematurely.
+	security           string // indicate the authentication protocol used by this server.
+	earlyFail          bool   // whether to error out the execution of a service handler prematurely.
+	multipleSetTrailer bool   // whether to call setTrailer multiple times.
 }
 
 func (s *testServer) EmptyCall(ctx context.Context, in *testpb.Empty) (*testpb.Empty, error) {
@@ -136,14 +141,21 @@ func (s *testServer) UnaryCall(ctx context.Context, in *testpb.SimpleRequest) (*
 		if err := grpc.SendHeader(ctx, md); err != nil {
 			return nil, grpc.Errorf(grpc.Code(err), "grpc.SendHeader(_, %v) = %v, want %v", md, err, nil)
 		}
-		grpc.SetTrailer(ctx, testTrailerMetadata)
+		if err := grpc.SetTrailer(ctx, testTrailerMetadata); err != nil {
+			return nil, grpc.Errorf(grpc.Code(err), "grpc.SetTrailer(_, %v) = %v, want <nil>", testTrailerMetadata, err)
+		}
+		if s.multipleSetTrailer {
+			if err := grpc.SetTrailer(ctx, testTrailerMetadata2); err != nil {
+				return nil, grpc.Errorf(grpc.Code(err), "grpc.SetTrailer(_, %v) = %v, want <nil>", testTrailerMetadata2, err)
+			}
+		}
 	}
 	pr, ok := peer.FromContext(ctx)
 	if !ok {
-		return nil, fmt.Errorf("failed to get peer from ctx")
+		return nil, grpc.Errorf(codes.DataLoss, "failed to get peer from ctx")
 	}
 	if pr.Addr == net.Addr(nil) {
-		return nil, fmt.Errorf("failed to get peer address")
+		return nil, grpc.Errorf(codes.DataLoss, "failed to get peer address")
 	}
 	if s.security != "" {
 		// Check Auth info
@@ -153,13 +165,13 @@ func (s *testServer) UnaryCall(ctx context.Context, in *testpb.SimpleRequest) (*
 			authType = info.AuthType()
 			serverName = info.State.ServerName
 		default:
-			return nil, fmt.Errorf("Unknown AuthInfo type")
+			return nil, grpc.Errorf(codes.Unauthenticated, "Unknown AuthInfo type")
 		}
 		if authType != s.security {
-			return nil, fmt.Errorf("Wrong auth type: got %q, want %q", authType, s.security)
+			return nil, grpc.Errorf(codes.Unauthenticated, "Wrong auth type: got %q, want %q", authType, s.security)
 		}
 		if serverName != "x.test.youtube.com" {
-			return nil, fmt.Errorf("Unknown server name %q", serverName)
+			return nil, grpc.Errorf(codes.Unauthenticated, "Unknown server name %q", serverName)
 		}
 	}
 	// Simulate some service delay.
@@ -229,9 +241,12 @@ func (s *testServer) FullDuplexCall(stream testpb.TestService_FullDuplexCallServ
 	md, ok := metadata.FromContext(stream.Context())
 	if ok {
 		if err := stream.SendHeader(md); err != nil {
-			return fmt.Errorf("%v.SendHeader(%v) = %v, want %v", stream, md, err, nil)
+			return grpc.Errorf(grpc.Code(err), "%v.SendHeader(%v) = %v, want %v", stream, md, err, nil)
+		}
+		stream.SetTrailer(testTrailerMetadata)
+		if s.multipleSetTrailer {
+			stream.SetTrailer(testTrailerMetadata2)
 		}
-		stream.SetTrailer(md)
 	}
 	for {
 		in, err := stream.Recv()
@@ -1193,6 +1208,76 @@ func testMetadataUnaryRPC(t *testing.T, e env) {
 	}
 }
 
+func TestMultipleSetTrailerUnaryRPC(t *testing.T) {
+	defer leakCheck(t)()
+	for _, e := range listTestEnv() {
+		testMultipleSetTrailerUnaryRPC(t, e)
+	}
+}
+
+func testMultipleSetTrailerUnaryRPC(t *testing.T, e env) {
+	te := newTest(t, e)
+	te.startServer(&testServer{security: e.security, multipleSetTrailer: true})
+	defer te.tearDown()
+	tc := testpb.NewTestServiceClient(te.clientConn())
+
+	const (
+		argSize  = 1
+		respSize = 1
+	)
+	payload, err := newPayload(testpb.PayloadType_COMPRESSABLE, argSize)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	req := &testpb.SimpleRequest{
+		ResponseType: testpb.PayloadType_COMPRESSABLE.Enum(),
+		ResponseSize: proto.Int32(respSize),
+		Payload:      payload,
+	}
+	var trailer metadata.MD
+	ctx := metadata.NewContext(context.Background(), testMetadata)
+	if _, err := tc.UnaryCall(ctx, req, grpc.Trailer(&trailer), grpc.FailFast(false)); err != nil {
+		t.Fatalf("TestService.UnaryCall(%v, _, _, _) = _, %v; want _, <nil>", ctx, err)
+	}
+	expectedTrailer := metadata.Join(testTrailerMetadata, testTrailerMetadata2)
+	if !reflect.DeepEqual(trailer, expectedTrailer) {
+		t.Fatalf("Received trailer metadata %v, want %v", trailer, expectedTrailer)
+	}
+}
+
+func TestMultipleSetTrailerStreamingRPC(t *testing.T) {
+	defer leakCheck(t)()
+	for _, e := range listTestEnv() {
+		testMultipleSetTrailerStreamingRPC(t, e)
+	}
+}
+
+func testMultipleSetTrailerStreamingRPC(t *testing.T, e env) {
+	te := newTest(t, e)
+	te.startServer(&testServer{security: e.security, multipleSetTrailer: true})
+	defer te.tearDown()
+	tc := testpb.NewTestServiceClient(te.clientConn())
+
+	ctx := metadata.NewContext(context.Background(), testMetadata)
+	stream, err := tc.FullDuplexCall(ctx, grpc.FailFast(false))
+	if err != nil {
+		t.Fatalf("%v.FullDuplexCall(_) = _, %v, want <nil>", tc, err)
+	}
+	if err := stream.CloseSend(); err != nil {
+		t.Fatalf("%v.CloseSend() got %v, want %v", stream, err, nil)
+	}
+	if _, err := stream.Recv(); err != io.EOF {
+		t.Fatalf("%v failed to complele the FullDuplexCall: %v", stream, err)
+	}
+
+	trailer := stream.Trailer()
+	expectedTrailer := metadata.Join(testTrailerMetadata, testTrailerMetadata2)
+	if !reflect.DeepEqual(trailer, expectedTrailer) {
+		t.Fatalf("Received trailer metadata %v, want %v", trailer, expectedTrailer)
+	}
+}
+
 // TestMalformedHTTP2Metedata verfies the returned error when the client
 // sends an illegal metadata.
 func TestMalformedHTTP2Metadata(t *testing.T) {
@@ -1601,8 +1686,8 @@ func testMetadataStreamingRPC(t *testing.T, e env) {
 		}
 	}
 	trailerMD := stream.Trailer()
-	if !reflect.DeepEqual(testMetadata, trailerMD) {
-		t.Fatalf("%v.Trailer() = %v, want %v", stream, trailerMD, testMetadata)
+	if !reflect.DeepEqual(testTrailerMetadata, trailerMD) {
+		t.Fatalf("%v.Trailer() = %v, want %v", stream, trailerMD, testTrailerMetadata)
 	}
 }
 

transport/transport.go

@@ -39,7 +39,6 @@ package transport // import "google.golang.org/grpc/transport"
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -287,19 +286,12 @@ func (s *Stream) StatusDesc() string {
 	return s.statusDesc
 }
 
-// ErrIllegalTrailerSet indicates that the trailer has already been set or it
-// is too late to do so.
-var ErrIllegalTrailerSet = errors.New("transport: trailer has been set")
-
 // SetTrailer sets the trailer metadata which will be sent with the RPC status
-// by the server. This can only be called at most once. Server side only.
+// by the server. This can be called multiple times. Server side only.
 func (s *Stream) SetTrailer(md metadata.MD) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.trailer != nil {
-		return ErrIllegalTrailerSet
-	}
-	s.trailer = md.Copy()
+	s.trailer = metadata.Join(s.trailer, md)
 	return nil
 }