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redis
Redis pubsub task cancellation raises ConnectionError
Version: 4.5.4
Platform: Windows / Linux - Python 3.10.10
Description: When cancelling a pubsub task that is listening for messages, the ConnectionError exception is thrown. This seems like an internal library problem because I can't catch the exception inside redis_subscribe function and the exception is thrown only after the CancellationError is raised inside the task.
Is this the intended behaviour? If so, what is an elegant work-around?
This code used to work in the previous versions of redis (4.5.3 an below).
redis_client is a global variable, initialized on the startup event of a server. The redis_subscribe function is supposed to be called inside endpoints that feed messages using websockets or server sent events. So the cancellation of the task needs to happen when for example a client disconnects from the server.
from redis.asyncio import Redis
import asyncio
redis_client = Redis()
async def redis_subscribe():
async with redis_client.pubsub() as pubsub:
pubsub.subscribe("channel")
async for message in pubsub.listen():
print(message)
task = asyncio.create_task(redis_subscribe())
asyncio.sleep(5)
task.cancel()
asyncio.sleep(5)
Task exception was never retrieved
future: <Task finished name='Task-27' coro=<Retry.call_with_retry() done, defined at redis/asyncio/retry.py:46> exception=ConnectionError('Connection closed by server.')>
Traceback (most recent call last):
File "redis/asyncio/retry.py", line 62, in call_with_retry
await fail(error)
File "redis/asyncio/client.py", line 779, in _disconnect_raise_connect
raise error
File "redis/asyncio/retry.py", line 59, in call_with_retry
return await do()
File "redis/asyncio/client.py", line 784, in _try_execute
return await command(*arg, **kwargs)
File "redis/asyncio/connection.py", line 840, in read_response
response = await self._parser.read_response(
File "redis/asyncio/connection.py", line 413, in read_response
await self.read_from_socket()
File "redis/asyncio/connection.py", line 396, in read_from_socket
raise ConnectionError(SERVER_CLOSED_CONNECTION_ERROR) from None
redis.exceptions.ConnectionError: Connection closed by server.
See https://github.com/redis/redis-py/pull/2666#issuecomment-1514452720 for the explanation why this happens. PR https://github.com/redis/redis-py/pull/2719 would potentially fix this.
@agronholm I don't think #2719 will fix it because it fixes the sync connection and this issue is in the async connection (maybe #2695 will fix it).
