Regression in v9 due to idle connection behavior change

[bduffany]

With go-redis v9, idle connections are now closed lazily, instead of proactively in the background like they were in v8. As a result, we're hitting redis client connection limits that we weren't hitting before, because we now have tons of idle connections (thousands of idle connections for each of our server instances that are connected to redis).

Some questions:

1. What was the reasoning for this change to close idle conns lazily instead of eagerly?
2. Is it possible to have ConnMaxIdleTime close the idle conns eagerly instead of lazily? The docs on MaxIdleConns say "The idle connections are not closed by default." but "by default" seems to imply there should be a way to get non-lazy behavior?

[ndyakov]

Hello @bduffany and thank you for opening this discussion. I cannot share about the reasoning, will dig deeper in the git history and get back to you if I find something.

[haunt98]

Is this PR #3418 cause this?
I also encounter this regression when I deploy version v9.16.0 recently.

I use metric pool_conn_idle_current from https://github.com/redis/go-redis/blob/master/extra/redisprometheus/README.md

Before:

After:

[ndyakov]

@haunt98 the original issue is for something else, feel free to open a new issue with detailed description what you are experiencing.Please include information about the "before" version as well

[ndyakov]

@haunt98 your problem should be addressed in v9.17.0 as for the initial issue reported here - I still don't have an answer why this change was done but can only assume it was so there are no reinitialization of connections done in the background if they are not used, this will be load on the server (and the client) that can be simply fixed with proper configuration

[haunt98]

Thanks @ndyakov, I will try and will report later

[ndyakov]

@bduffany i would suggest optimising the client options to use lower number of connections if you would wish to close them sooner. Seems like this change was by design in v9. We will play around with different approaches for v10, but overall this won't change right now and may never change. the lazy close of connections seems more efficient and easy to work with.