[ray] Async actor not working in local mode.

What is the problem?

Async actor is not being recognized in local mode. cc: @ijrsvt

Ray version and other system information (Python version, TensorFlow version, OS):

• ray version: latest master
• python: 3.7.4
• OS: macos 10.15.3.

Reproduction

import ray 
ray.init(local_mode=True)

@ray.remote
class test_actor:
    async def start(self):
        return 1
actor = test_actor.remote()
ray.get(actor.start.remote())

The error I’m getting

E0507 17:19:21.404151 381615552 core_worker.cc:1082] Pushed Error with JobID: 0100 of type: task with message: ray::test_actor.start() (pid=60331, ip=192.168.0.7)
  File "python/ray/_raylet.pyx", line 464, in ray._raylet.execute_task
  File "python/ray/_raylet.pyx", line 465, in ray._raylet.execute_task
  File "python/ray/_raylet.pyx", line 1136, in ray._raylet.CoreWorker.store_task_outputs
  File "/Users/allenyin/Test/ray/python/ray/serialization.py", line 401, in serialize
    return self._serialize_to_msgpack(metadata, value)
  File "/Users/allenyin/Test/ray/python/ray/serialization.py", line 373, in _serialize_to_msgpack
    self._serialize_to_pickle5(metadata, python_objects)
  File "/Users/allenyin/Test/ray/python/ray/serialization.py", line 353, in _serialize_to_pickle5
    raise e
  File "/Users/allenyin/Test/ray/python/ray/serialization.py", line 350, in _serialize_to_pickle5
    value, protocol=5, buffer_callback=writer.buffer_callback)
  File "/Users/allenyin/Test/ray/python/ray/cloudpickle/cloudpickle_fast.py", line 72, in dumps
    cp.dump(obj)
  File "/Users/allenyin/Test/ray/python/ray/cloudpickle/cloudpickle_fast.py", line 617, in dump
    return Pickler.dump(self, obj)
TypeError: can't pickle coroutine objects at time: 1.5889e+09

• I have verified my script runs in a clean environment and reproduces the issue.
• I have verified the issue also occurs with the latest wheels.

[nirvana-msu]

I would argue with this not being a common use-case. Sure, you’re not gonna run Ray in Local mode in production - but you may have to do it during development for debugging purposes. And since async actors are not supported in local mode - it means you simply cannot use them in your code. That is unless you’re prepared to maintain two versions of your code - one with async actors for production, and one with sync actors for development… who would want to do that?

It would not have been an issue for me if not for debugging requirements. #14005 could be an alternative solution here (that would enable seamless debugging of workers/actors in PyCharm in non-local mode).

[bkatwal]

The same problem I am facing too. As I am testing my actor. Earlier I had used ray.init() unfortunately, this does not record test coverage. To test i changed to local_mode=True. Now the problem is my actor’s remote function call never returns, as the actor code runs infinitely 😦