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Python websockets: how to override sync method WebSocketCommonProtocol.connection_made() with async call?

Currently WebSocketCommonProtocol.connection_made() is defined as a sync call. If I want override it and add some async call, it seems no way to do it.

WebSocketCommonProtocol.connection_made()

Example: I use aioredis to talk to Redis; but I cannot use aioredis when overriding WebSocketCommonProtocol.connection_made(). The only workaround I can think out is using a sync library redis-py in this function, but use aioredis in other places. It works but very ugly.

WebSocketCommonProtocol.connection_made()

asgiref.sync.async_to_sync() doesn't work here: I already have event loop running. This commit will prevent me from using it: https://github.com/django/asgiref/commit/9d42cb57129bd8d94a529a5c95dcf9f5d35a9beb

asgiref.sync.async_to_sync()

WebSocketCommonProtocol.connection_made() is inherited from asyncio.StreamReaderProtocol.connection_made(). So this is a generic question even for python standard library. Don't know whether anyone knows a solution already.

WebSocketCommonProtocol.connection_made()

asyncio.StreamReaderProtocol.connection_made()

Please give me some suggestions to solve this issue.

connection_made

loop.create_task(async_function(args...))

connection_made

1 Answer
1

Worked out one solution: https://pypi.org/project/syncasync/

It will run the async code in a new thread. So it will not have a race condition with the sync code. This approach is very slow: the main thread will wait for the sync code, and the sync code will wait for the new thread to finish.

Compared to the other solution: use both sync and async libraries in your program, this solution will allow you to only use async library.

Give it a try and let me know any bugs, or suggest a better approach.

Example:

#!/usr/bin/env python

import asyncio

from syncasync import async_to_sync


class Base:
def method(self):
pass

def run(self):
self.method()


class Derived(Base):
@async_to_sync
async def method(self):
await asyncio.sleep(0)


async def test():
d = Derived()
d.run()


if __name__ == '__main__':
asyncio.get_event_loop().run_until_complete(test())


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