AbstractConnection.register_connect_callback was made private in version 5.0.1

[woutdenolf]

Version: redis-py 5.0.1

Platform: Ubuntu 20.04

Description:

In #2870 the public API of AbstractConnection changed

# redis-py 5.0.0

class AbstractConnection:
    def register_connect_callback(self, callback):

# redis-py 5.0.1

class AbstractConnection:
    def _register_connect_callback(self, callback):

We use the public method register_connect_callback in our code:

  File "/home/denolf/dev/bliss/blissdata/blissdata/redis/caching.py", line 150, in _create_invalidation_connection
    connection.register_connect_callback(stop_callback)
AttributeError: 'UnixDomainSocketConnection' object has no attribute 'register_connect_callback'

[woutdenolf]

Ping @kristjanvalur

[kristjanvalur]

Ah, this was done as a result to this comment here: #2870 (comment)
by @chayim. These apis were supposed to be internal, I guess, since they were designed for the PubSub class, I gather. There previously was no "unregister" (only clear) and so it wasn't really well suited for non-library code.
I'm happy to change it back, to remove the underscore, if that is what the maintainers decide.

[woutdenolf]

Same goes for clear_connect_callbacks: it was replace by _deregister_connect_callback.

[kristjanvalur]

Yes, that one was problematic because it clears them all, not just the one you registered. But it is not really needed because the callbacks are weak anyway.

[hiimdoublej-swag]

Hello @kristjanvalur,
We have a use case that is currently achieved by registering our own callbacks using register_connect_callback
Are there plans to bring the public functions back ?

[kristjanvalur]

Well, I'm not a maintainer here, just a submitter of pull-requests. I can prepare one where we move these functions back, but it is up to the maintainers whether they want them. I think it would help your argument if you could explain your use case, because as I understand, these apis were only ever intended to be private to begin with.

[hiimdoublej-swag]

@chayim Need your opinion on restoring these functions, please kindly take a look at this thread, thanks.

[woutdenolf]

We use it for client side caching in which you need to set TRACKING on upon connecting (off when disconnecting) to invalidate client side cache when a value changes on the server.

[kristjanvalur]

We use it for client side caching in which you need to set TRACKING on upon connecting (off when disconnecting) to invalidate client side cache when a value changes on the server.

cool use case. Yes, I totally get it, the client needs to know when the connection was automatically re-connected in order to enable tracking again. Who knows what other ephemeral connection state a client might want to set on a re-connected connection?

I'll prepare a PR making those non-semi-private again, lets see what the maintainers think. I can't be bothered to document those though :)

[hiimdoublej-swag]

ping @chayim

[kristjanvalur]

in the mean-time, these aren't private-private, you can continue to use them with the leading underscore. It is called hacking and all the cool kids are doing it, I'm told.

[syphar]

Just to add here, register_connect_callback is used by the celery redis result backend:
https://github.com/celery/celery/blob/0bc89cc594638e1d88655764807fcc59fb32efc6/celery/backends/redis.py#L122

So with redis-py 5.0.1 we see errors with checking celery results in some cases

I can dig deeper if more information is needed, will skip 5.0.1 as a quickfix

[Shineaki]

Thanks for this post, I just ran into this bug and wasn't sure what to make of it:

Exception ignored in: <function AsyncResult.__del__ at 0x7f7222a3b9d0> Traceback (most recent call last): File "/usr/local/lib/python3.9/site-packages/celery/result.py", line 417, in __del__ self.backend.remove_pending_result(self) File "/usr/local/lib/python3.9/site-packages/celery/backends/asynchronous.py", line 208, in remove_pending_result self.on_result_fulfilled(result) File "/usr/local/lib/python3.9/site-packages/celery/backends/asynchronous.py", line 216, in on_result_fulfilled self.result_consumer.cancel_for(result.id) File "/usr/local/lib/python3.9/site-packages/celery/backends/redis.py", line 184, in cancel_for self._pubsub.unsubscribe(key) File "/usr/local/lib/python3.9/contextlib.py", line 137, in __exit__ self.gen.throw(typ, value, traceback) File "/usr/local/lib/python3.9/site-packages/celery/backends/redis.py", line 130, in reconnect_on_error self._ensure(self._reconnect_pubsub, ()) File "/usr/local/lib/python3.9/site-packages/celery/backends/redis.py", line 384, in ensure return retry_over_time( File "/usr/local/lib/python3.9/site-packages/kombu/utils/functional.py", line 318, in retry_over_time return fun(*args, **kwargs) File "/usr/local/lib/python3.9/site-packages/celery/backends/redis.py", line 122, in _reconnect_pubsub self._pubsub.connection.register_connect_callback(self._pubsub.on_connect) AttributeError: 'SSLConnection' object has no attribute 'register_connect_callback'

• Redis = 5.0.1
• Celery = 5.3.6

[dvora-h]

Fixed in #2980