Fix/22

[pwoolvett]

• test: add concurrent checks

  • group together fixtures for backend testing
  • Add per-backend setup to allow slow initialization.
    This is specially important as kafka subscribe can return while the consumer
    is not ready. See related test setup upstream:
    • https://github.com/aio-libs/aiokafka/blob/2c54e10c57760f779961a8c2f5df8ad609ef6983/tests/test_consumer.py#L433
    • https://github.com/aio-libs/aiokafka/blob/2c54e10c57760f779961a8c2f5df8ad609ef6983/tests/_testutil.py#L376
    • https://github.com/aio-libs/aiokafka/blob/2c54e10c57760f779961a8c2f5df8ad609ef6983/tests/_testutil.py#L364

• chore: update remnants, packages

• fix(backend/kafka): consumer unsubscribe not awaitable

• fix(backend/postgres): allow concurrent pubs

  This fix adds a lock (asyncio.Event based) to avoid
  asyncpg.exceptions._base.InterfaceError: cannot perform operation: another operation is in progress

fixes #22
fixes #42

[amacfie]

Wouldn't it be simpler to use asyncio.Lock?

[pwoolvett]

Simpler, and better.

[skyforeverRivian]

recently, my project facing some issue

File "*****/python3.9/site-packages/broadcaster/_base.py", line 62, in connect
    await self._backend.connect()
AttributeError: 'Broadcast' object has no attribute '_backend'

seems like this PR doesn't resolve slow backend initialization issue

[logankaser]

Why didn't this merge? If I fixed its conflicts, would it be accepted?

[alex-oleshkevich]

@logankaser let's have it split into multiple PRs. I believe there is only one issue related to postgres left.

[logankaser]

I think there are two:

1. This issue, the connection is not guarded by a lock, so it can be accessed while the connection is active.
   Can be with using a asyncio lock like this PR did, or better something like https://github.com/permitio/broadcaster/blob/master/broadcaster/_backends/postgres.py
2. Postgres backend: handle connection loss #66 Postgres backend cannot gracefully handle connection loss

[alex-oleshkevich]

#66 looks like a good merge candidate, but I did not test it yet.