Cythonized async python gRPC server not working

Question

I have to cythonize a python script which contains an asyncio gRPC server.
The script is working well when is running with Python. I've written a non asyncio version of the script and both python and cythonized variants are working without any problems.
The only problem is when using asyncio + cythonization.

spam.proto

syntax = "proto3";

message EchoRequest {
  string data = 1;
}

message EchoResponse {
  string data = 1;
}

service Spam {
  rpc Echo (EchoRequest) returns (EchoResponse);
  rpc EchoStream (stream EchoRequest) returns (stream EchoResponse);
}

srv.py

import asyncio
import grpc
import spam_pb2
import spam_pb2_grpc


class Spam(spam_pb2_grpc.SpamServicer):

    async def Echo(self, request, context):
        response = spam_pb2.EchoResponse(data=request.data)
        return response

    async def EchoStream(self, request_iterator, context):
        async for request in request_iterator:
            response = spam_pb2.EchoResponse(data=request.data)
            yield response


async def main():
    server = grpc.aio.server()
    spam_pb2_grpc.add_SpamServicer_to_server(Spam(), server)
    server.add_insecure_port('0.0.0.0:60000')
    await server.start()
    await server.wait_for_termination()


if __name__ == '__main__':
    asyncio.run(main())

cli.py

import asyncio
import time

import grpc
import spam_pb2
import spam_pb2_grpc


async def _yield_request():
    for _ in range(3):
        yield spam_pb2.EchoRequest(data=time.asctime())


async def main():
    channel = grpc.aio.insecure_channel('localhost:60000')
    stub = spam_pb2_grpc.SpamStub(channel)

    response = await stub.Echo(spam_pb2.EchoRequest(data=time.asctime()))
    print(response)

    response_iterator = stub.EchoStream(_yield_request())
    async for response in response_iterator:
        print(response)


if __name__ == '__main__':
    asyncio.run(main())

gen-pb2.sh

#!/bin/sh

python -m grpc_tools.protoc --proto_path=. --python_out=. --grpc_python_out=. spam.proto

build.sh

#!/bin/sh

cython -3 --embed --output-file srv.c srv.py
gcc $(pkg-config --cflags python3) srv.c -o srv -lpython3.8

srv

$ PYTHONPATH=$PYTHONPATH:venv/lib/python3.8/site-packages ./srv 
/usr/lib/python3.8/asyncio/base_events.py:1860: RuntimeWarning: coroutine 'Spam.Echo' was never awaited
  handle = None  # Needed to break cycles when an exception occurs.

stub.Echo()

$ python cli.py 
Traceback (most recent call last):
  File "cli.py", line 27, in <module>
    asyncio.run(main())
  File "/usr/lib/python3.8/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.8/asyncio/base_events.py", line 616, in run_until_complete
    return future.result()
  File "cli.py", line 18, in main
    response = await stub.Echo(spam_pb2.EchoRequest(data=time.asctime()))
  File "/home/slava/cython-grpc-aio/venv/lib/python3.8/site-packages/grpc/aio/_call.py", line 290, in __await__
    raise _create_rpc_error(self._cython_call._initial_metadata,
grpc.aio._call.AioRpcError: <AioRpcError of RPC that terminated with:
    status = StatusCode.UNKNOWN
    details = "Unexpected <class 'TypeError'>: descriptor 'SerializeToString' for 'google.protobuf.pyext._message.CMessage' objects doesn't apply to a 'coroutine' object"
    debug_error_string = "{"created":"@1636478705.359130370","description":"Error received from peer ipv6:[::1]:60000","file":"src/core/lib/surface/call.cc","file_line":1069,"grpc_message":"Unexpected <class 'TypeError'>: descriptor 'SerializeToString' for 'google.protobuf.pyext._message.CMessage' objects doesn't apply to a 'coroutine' object","grpc_status":2}"
>

stub.EchoStream()

$ python cli.py 
Traceback (most recent call last):
  File "cli.py", line 27, in <module>
    asyncio.run(main())
  File "/usr/lib/python3.8/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.8/asyncio/base_events.py", line 616, in run_until_complete
    return future.result()
  File "cli.py", line 22, in main
    async for response in response_iterator:
  File "/home/slava/cython-grpc-aio/venv/lib/python3.8/site-packages/grpc/aio/_call.py", line 326, in _fetch_stream_responses
    await self._raise_for_status()
  File "/home/slava/cython-grpc-aio/venv/lib/python3.8/site-packages/grpc/aio/_call.py", line 236, in _raise_for_status
    raise _create_rpc_error(await self.initial_metadata(), await
grpc.aio._call.AioRpcError: <AioRpcError of RPC that terminated with:
    status = StatusCode.UNKNOWN
    details = "Unexpected <class 'TypeError'>: 'async_generator' object is not iterable"
    debug_error_string = "{"created":"@1636479008.742822012","description":"Error received from peer ipv6:[::1]:60000","file":"src/core/lib/surface/call.cc","file_line":1069,"grpc_message":"Unexpected <class 'TypeError'>: 'async_generator' object is not iterable","grpc_status":2}"
>

Cythonized async python gRPC server not working

0 Answers0