GRPC C++ client finish() blocks forever with Golang server

Question

I have a C++ gRPC client and Golang gRPC server. For a bi-directional stream, when the client wants to close the stream, it blocks forever on the call to Finish().

This only happens if there is no error, that is, the server rpc function returns nil. If the server was written in C++, I understand it would have returned Status::Ok.

If the Golang server returns a non-nil error, then the Finish() function returns as expected. The problem occurs only in the case of no error.

Example:

.proto

service StreamTest {
  rpc Get(stream StreamCommand) returns (stream Result) {}
}
message StreamCommand{
  string cmd = 1;
}
message Result {
  string res = 1;
}

.cpp

std::unique_ptr<ClientReaderWriter<StreamCommand, Result>> readerWriter;
bool Get(Result &res) {
    return readerWriter->Read(&res);
}

bool CloseClient() {
    StreamCommand cmd;
    cmd.set_cmd("stop");
    readerWriter->Write(cmd);
    readerWriter->WritesDone();
    Status status = readerWriter->Finish(); // <------ BLOCKING
    return status.ok();
}

I have tested the server with a Golang gRPC client and it works fine. Should the server return something other than a nil error? Should I report this as a bug?

Any help is appreciated! Thanks!

Answer 1

I am not familiar with Go, but I know c++ layer. Can you run the client with GRPC_VERBOSITY=debug and GRPC_TRACE=api? That would give more insight into the problem.