fix MPEngine poll

[grimoire]

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[Copilot]

Pull request overview

This PR adjusts the ZMQ-based RPC server loop used by the multi-process PyTorch engine, aiming to improve/repair polling behavior in AsyncRPCServer.run().

Changes:

• Reworked the server’s poll loop to drain queued socket events via repeated non-blocking polls.
• Removed the init_event wait when starting streaming RPC calls (now responds with stream_id immediately).

Comments suppressed due to low confidence (1)

lmdeploy/pytorch/engine/mp_engine/zmq_rpc.py:158

• Removing the init_event wait introduces a race: the client can receive the stream_id and call _asyncrpcserver_get_stream_output before _method_async_streaming_task has populated self.stream_output[stream_id], which will raise ValueError('Stream ID ... not found') and can make streaming calls flaky (e.g., tests/pytorch/engine/test_zmq_rpc.py streaming case). Please ensure the stream state is created before replying (e.g., restore await init_event.wait() before sending the response, or pre-create self.stream_output[stream_id] synchronously in call_method_async and let the task only fill results).

            response = dict(success=True, request_id=request_id, result=stream_id)
            session_id = kwargs.get('session_id', None)
            if session_id is None:
                session_id = args[0]
            self.send_multipart(client_id, response)

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[RunningLeon]

LGTM