KAFKA-19734 Adding application tag to clientstate metric

[gensericghiro]

Summary

As a follow-on to the improvements introduced in
KIP-1091
it would be useful to add the application-id as a tag to the
client-state metric. This allows Kafka Streams developers and
operators to connect metrics containing a thread-id (which embeds the
application-id) across separate deployments of Kafka Streams
instances, which are members of the same logical application.

Reviewers: Bill Bejeck[email protected] Matthias
Sax[email protected]

[bbejeck]

Thanks for the PR @gensericghiro! Can you update/add a test to StreamsMetricsImplTest otherwise lgtm

[mjsax]

Don't forget doc updates -> https://github.com/apache/kafka/blob/trunk/docs/ops.html#L3003 and https://github.com/apache/kafka/blob/trunk/docs/ops.html#L3040 plus https://github.com/apache/kafka/blob/trunk/docs/streams/upgrade-guide.html

[bbejeck]

Thanks @gensericghiro LGTM

[bbejeck]

Merged #20766 into trunk

[bbejeck]

@gensericghiro let's do the documentation in a follow-up PR

[chia7712]

Pardon me. I see this new tag applied al all metrics, yet the KIP only specifies the client-state metric. Am I misunderstanding the scope? thanks!

[gensericghiro]

You're right, good catch. It doesn't seem like I can add a tag for a specific metric however. Since addClientStateTelemetryMetric is calling the generic addClientLevelMutableMetric method, where tags get added, we'd need to add conditional logic there, which I don't think is something we want.

[bbejeck]

@chia7712 - thanks for pointing this out. I'm going to start a discussion on the mailing list with a couple of options on how to address the situation.