Multi-thread support for python asyncio gRPC clients

[Michael McCarthy]

Hi folks,

I have an asyncio gRPC client that is used in a multithreaded environment. When multiple threads connect to the service via the client simultaneously, I see a stream of the following errors:

2021-01-27 09:33:56,937 ERROR [asyncio] [thread_0] Exception in callback PollerCompletionQueue._handle_events()() handle: )()> Traceback (most recent call last): File "/usr/local/lib/python3.8/asyncio/events.py", line 81, in _run self._context.run(self._callback, *self._args) File "src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pyx.pxi", line 147, in grpc._cython.cygrpc.PollerCompletionQueue._handle_events BlockingIOError: [Errno 11] Resource temporarily unavailable 2021-01-27 09:33:56,937 ERROR [asyncio] [thread_1] Exception in callback PollerCompletionQueue._handle_events()() handle: )()> Traceback (most recent call last): File "/usr/local/lib/python3.8/asyncio/events.py", line 81, in _run self._context.run(self._callback, *self._args) File "src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pyx.pxi", line 147, in grpc._cython.cygrpc.PollerCompletionQueue._handle_events BlockingIOError: [Errno 11] Resource temporarily unavailable

The requests appear to be completing successfully, however, the messages are flooding my logs and making me nervous!

In my tests, each thread creates its own channel and submits its own async requests. The errors occur regardless of the load on the service. The errors do not occur if the clients are running in different processes.

My setup:

• Python version: 3.8.6
• grpcio version: 1.35.0

Is the behaviour expected? Any insight is appreciated!

I've also created this SO post.

[Lidi Zheng]

Answered in the SO post. Let's continue the discussion there.