Make use of LabelHints.Limit for label names and values requests

[charleskorn]

Is your feature request related to a problem? Please describe.

#8780 brings in prometheus/prometheus#14109, which allows storage implementations to know that the label names or label values request has a limit applied.

However, we currently don't make use of this information, so ingesters and store-gateways may do a bunch of work retrieving values that will then be thrown away in the querier.

Describe the solution you'd like

Pass the limit to ingesters and store-gateways, and modify them so they never return more values than the limit allows.

Describe alternatives you've considered

(none)

Additional context

prometheus/prometheus#12795 has more context on this functionality.

[AidanKenney]

Hi @charleskorn, I'd like to give this a shot and get more familiar with this project.

Am I on the right track to think that LabelHints.Limit will need to be passed down to the implementations of LabelNames and LabelValues on the StoreGatewayServer interface?

[charleskorn]

Hi @charleskorn, I'd like to give this a shot and get more familiar with this project.

Awesome, thanks!

Am I on the right track to think that LabelHints.Limit will need to be passed down to the implementations of LabelNames and LabelValues on the StoreGatewayServer interface?

Yep, that's right. We'll also need a similar change for ingesters, but we could do that as a separate PR.

[samyakjain10]

Hi @charleskorn , just checking if the issue is up for grab since it has been quite sometime that the PR has not been raised

[charleskorn]

That would be a question for @AidanKenney - are you still interested in working on this issue?

[AidanKenney]

Thanks @charleskorn, still interested but haven't had the time I hoped for to dig into this. @samyakjain10 feel free to work on it.

[santileira]

@AidanKenney / @charleskorn / @samyakjain10 could I work on this feature? It doesn't have updates since September (3 months ago).

[santileira]

@AidanKenney / @charleskorn / @samyakjain10 working on it.

[santileira]

@aknuds1 I think that you are maintainer and you can help me here, is this still an issue that we want to fix? I'm about to start working on this but I want to be sure that we still want this. Thanks

[santileira]

hey @dimitarvdimitrov. I saw you commenting and discussing in other issues. Could you help me to understand if this is still important and we should fix it? If so, I'm happy to work on it. Thanks :)

[aknuds1]

@santileira hi - yes, @charleskorn has more context than me, but I should think we'd still like to fix this issue.

[charleskorn]

Hi @santileira, sorry for the slow response, I've been on leave.

I don't believe we've implemented this yet and it would be a nice improvement, so if you'd like to work on it, that would be great.

[santileira]

Hi @charleskorn, @dimitarvdimitrov and @aknuds1! PR (#10410) is ready for review. Could you take a look at it and give me feedback? Thanks