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 @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.

@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.

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.

Hi @AndrewJSchofield . The KIP has been accepted, Thanks a lot!

So we can move forward now. I built the client SDK with the branch and tested it with the following cases today. I think the results meet my expectations. I’m sharing them with you for your review! Thanks!

Case 1

kafka 4.1
client: set the rack and group.protocol=consumer
test result:
[(memberId=9Qlf0K6gSzC1FZ6hcTHxPg, groupInstanceId=null, rackId=us-east-1a, clientId=consumer-new_consume_group-1, host=/10.224.49.116, assignment=(topicPartitions=test_topic-2,test_topic-1,test_topic-0), targetAssignment=Optional[(topicPartitions=test_topic-2,test_topic-1,test_topic-0)], memberEpoch=1, upgraded=true)]

Case 2

kafka 4.1
client: set the rack only
test result:
[(memberId=Lcg5NrPXQrK04J6Txz3E6w, groupInstanceId=null, rackId=null, clientId=consumer-new_consume_group-1, host=/10.224.49.116, assignment=(topicPartitions=test_topic-1,test_topic-0,test_topic-2), targetAssignment=Optional.empty, memberEpoch=null, upgraded=null)]

Case 3

kafka3.9
client: set the rack
test result:
[(memberId=3dc3-419e-a7ee-f112bfc622ac, groupInstanceId=null, rackId=null, clientId=5488f769c8-vl97x, host=/10.51.88.67, assignment=(topicPartitions=test_topic-0), targetAssignment=Optional.empty, memberEpoch=null, upgraded=null),

Case 4

kafka 4.1-Share Group
server: group.share.enable=true
client: set the rack
test result:
[(memberId=tjq3E3xdQ9S6UB1wIkQL7w, rackId=us-east-1a, clientId=consumer-new_consume_group_shard-1, host=/10.224.49.116, assignment=(topicPartitions=test_topic-1,test_topic-0,test_topic-2), memberEpoch=2)]

Case 5

kafka 4.1-Share Group
server: group.share.enable=true
client: no set the rack
test result:
[(memberId=xq-7K6o_SBWao-_E7ER-Gw, rackId=null, clientId=consumer-new_consume_group_shard2-1, host=/10.224.49.116, assignment=(topicPartitions=test_topic-2,test_topic-1,test_topic-0), memberEpoch=2)]

@AndrewJSchofield Done for all the changed. Help to review it again. Really appreciate it!

@AndrewJSchofield Thank you so much for your thorough review and continuous follow-up — really appreciate it!

@jiafu1115 Thanks for your first KIP.