fix TestDial_Tracing/stream flaking

There was a previous attempt at synchronizing the test by waiting
for the server to close the stream. There is another race in the test
as well though.

The client first sends the stream close to the server and then goes off to finish
the client span. If the server receives the client stream closing before
the client managed to finish its span, the server will race finishing
its 'nested span' with the client's '/mwitkow.testproto/TestService/PingStream'
span.

This commit fixes the race by synchronizing the server's stream handler to only
proceed after the client has returned from the CloseSend method.

1 files changed, 13 insertions, 0 deletions

diff --git a/client/dial_test.go b/client/dial_test.go
index b5f3fc6c8..b9a1dabe2 100644
--- a/client/dial_test.go
+++ b/client/dial_test.go
@@ -252,6 +252,8 @@ func TestDial_Tracing(t *testing.T) {
 	listener, err := net.Listen("unix", serverSocketPath)
 	require.NoError(t, err)
 
+	clientSendClosed := make(chan struct{})
+
 	// This is our test service. All it does is to create additional spans
 	// which should in the end be visible when collecting all registered
 	// spans.
@@ -267,6 +269,14 @@ func TestDial_Tracing(t *testing.T) {
 			return &proxytestdata.PingResponse{}, nil
 		},
 		PingStreamMethod: func(stream proxytestdata.TestService_PingStreamServer) error {
+			// synchronize the client has returned from CloseSend as the client span finishing
+			// races with sending the stream close to the server
+			select {
+			case <-clientSendClosed:
+			case <-stream.Context().Done():
+				return stream.Context().Err()
+			}
+
 			span, _ := opentracing.StartSpanFromContext(stream.Context(), "nested-span")
 			defer span.Finish()
 			span.LogKV("was", "called")
@@ -363,6 +373,9 @@ func TestDial_Tracing(t *testing.T) {
 		stream, err := proxytestdata.NewTestServiceClient(cc).PingStream(ctx)
 		require.NoError(t, err)
 		require.NoError(t, stream.CloseSend())
+		close(clientSendClosed)
+
+		// wait for the server to finish its spans and close the stream
 		resp, err := stream.Recv()
 		require.Equal(t, err, io.EOF)
 		require.Nil(t, resp)