feat: Implemented redis.asyncio.SentinelBlockingConnectionPool.

[DABND19]

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Description of change

Added redis.asyncio.SentinelBlockingConnectionPool class

[DABND19]

@dvora-h Hello! How can I improve this pull request so that it gets reviewed?
And what's wrong with this pull request, which does some of the things I did in the current one, but at the same time it has been hanging around for a long time without approval?

[dvora-h]

@vladvildanov

[vladvildanov]

What is the purpose of this proxy class? get_master_address and rotate_slaves methods implementations are exactly the same as in SentinelConnectionPool class. The only difference that I see is the missing calls to parent object in constructor and reset.

[DABND19]

I did it this way because it is already done in the synchronous version: https://github.com/redis/redis-py/blob/master/redis/sentinel.py#L89

[vladvildanov]

Yeah, I get it. It's a bad design approach and I don't want to spread it even more. It should be implemented correctly and I will create an issue for the future to do the same with sync version.

[DABND19]

Okay. I'll think about a better solution

[vladvildanov]

The best solution will be refactor async ConnectionPool the way we don't need to use workarounds to break inheritance limitations

[DABND19]

Hello. What if we move BlockingConnectionPool logic to ConnectionPool?
We can do something like this:

from typing import Optional


# If the timeout parameter is zero, then we have the old behavior,
# else we have a blocking connection pool
class ConnectionPool:
    def __init__(
        self,
        timeout: Optional[int] = 0,
        **kwargs,
    ) -> None:
        ...


# For backward compatibility
class BlockingConnectionPool(ConnectionPool):
    def __init__(self, timeout: Optional[int] = 20, **kwargs) -> None:
        super().__init__(timeout=timeout, **kwargs)

[vladvildanov]

Well, conceptually proxies are used to add an additional functionality before or after we want to access the original object. But here proxy are used just to override super class methods that breaks the functionality of child.

Proxy here is the workaround, to hide a problem with inheritance that we have. We have to either fix it in ConnectionPool so it can be inheritable, or doesn't inherit this at all

[cavemanpi]

@vladvildanov suggested I come over here as well. I have a PR which seems tangentially related. Any others care to give feedback on the idea expressed in this comment? #3359 (comment)