grpc python library server streaming issue

[sam reddy]

a simple grpc server client, client send a int and server streams int's back.

client is reading the messages one by one but server is running the generator function immediately for all responses.

server code: 

    import test_pb2_grpc as pb_grpc
    import test_pb2 as pb2
    import time
    import grpc
    from concurrent import futures


    class test_servcie(pb_grpc.TestServicer):


        def Produce(self, request, context):
            for i in range(request.val):
                print("request came")
                rs = pb2.Rs()
                rs.st = i + 1
                yield rs






        def serve():




            server =
            grpc.server(futures.ThreadPoolExecutor(max_workers=10))
            pb_grpc.add_TestServicer_to_server(test_servcie(), server)
            server.add_insecure_port('[::]:50051')
            print("service started")
            server.start()
            try:
                while True:
                    time.sleep(3600)
            except KeyboardInterrupt:
                server.stop(0)




    if __name__ == '__main__':
        serve()

client code:

 

   import grpc
    import test_pb2_grpc as pb_grpc
    import test_pb2 as pb
    def test():
        channel = grpc.insecure_channel(
        '{host}:{port}'.format(host="localhost", port=50051))


        stub = pb_grpc.TestStub(channel=channel)


        req = pb.Rq()
        req.val = 20
        for s in stub.Produce(req):
            print(s.st)
            import time
            time.sleep(10)


    test()

proto file:
    syntax = "proto3";


    service Test {
        rpc Produce (Rq) returns (stream Rs);
    }


    message Rq{
     int32 val = 1;
    }
    message Rs{
     int32 st = 1;
    }

after starting the server

when i run the client, server side generator started running and completed immediately it looped for the range.

what i expected is it will one by one as client calls but that is not the case.

is this an expected behaviour. my client is still printing the values but the sever is already completed the function.

[Ken Payson]

This behavior is expected for a unary request/stream response rpc.

If you want the service handler to loop over requests, you should use bidirectional streaming (stream request/ stream response).

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