KAFKA-19784: Expose rack ID in MemberDescription and ShareMemberDescription

[jiafu1115]

Hi Team:

Currently, the AdminClient’s describeConsumerGroups API returns a
MemberDescription that does not include rack information, even though
the underlying ConsumerGroupDescribeResponse protocol already supports a
rackId field. This causes users to be unable to retrieve member rack
information through the Admin API.

Rack information is crucial for:

Monitoring and visualization tools > Operational analysis of rack
distribution > Diagnosing rack-aware assignment issues

In addition, StreamsGroupMemberDescription already includes the rackId,
so adding it here would make the behavior more consistent.

BTW, I have currently implemented our AZ/Rack analysis using a
workaround — passing the rack information into the clientId field and
parsing it afterward.

kafkaConsumerConfig.customConfig(ConsumerConfig.CLIENT_ID_CONFIG,
generateClientIdWithRack(ip, rack));

So I propose this change with tiny code change to support this feature.

Thanks for review!

[AndrewJSchofield]

Hi @jiafu1115 . Thanks for the PR. This would be a tiny change to a public interface and that means it needs an accompanying KIP. It would be a small KIP and not at all controversial I think. Would you like to create the KIP or would you like me to do this? Also, note that MemberDescription is also used by share groups, and those too are able to fill in the rack ID using information already present in the protocol response.

[jiafu1115]

Hi @jiafu1115 . Thanks for the PR. This would be a tiny change to a public interface and that means it needs an accompanying KIP. It would be a small KIP and not at all controversial I think. Would you like to create the KIP or would you like me to do this? Also, note that MemberDescription is also used by share groups, and those too are able to fill in the rack ID using information already present in the protocol response.

Hi. @AndrewJSchofield Thanks for your review and reminder. I will create one KIP for the workflow and check the shared group code according to your suggestion.

[jiafu1115]

@AndrewJSchofield Update: KIP https://cwiki.apache.org/confluence/display/KAFKA/KIP-1227%3A+Expose+Rack+ID+in+MemberDescription+and+ShareMemberDescription created and I also updated the change for share group. We can wait one week before the vote to collect feedbacks though it is one tiny change.

[jiafu1115]

Update: I fixed the compile/check style issues and squashed the commits.
BTW, it seems the test is flaky, regardless of the changes in this PR.