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https://issues.apache.org/jira/browse/KAFKA-17116?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17869467#comment-17869467
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Kirk True commented on KAFKA-17116:
-----------------------------------
My understanding is:
# This is an edge case
# The broker contains logic to remove stale members
If the above two statements are true, what's the downside of letting the broker
handle the member as it does today, namely removing it after some configured
amount of time?
I agree that it makes sense to augment the client logic to only send the 'leave
group' request if we have a member ID. At this point, I'm -1 on the idea of
introducing temporary IDs to handle edge cases like this.
> New consumer may not send effective leave group if member ID received after
> close
> ----------------------------------------------------------------------------------
>
> Key: KAFKA-17116
> URL: https://issues.apache.org/jira/browse/KAFKA-17116
> Project: Kafka
> Issue Type: Bug
> Components: clients, consumer
> Affects Versions: 3.8.0
> Reporter: Lianet Magrans
> Assignee: TengYao Chi
> Priority: Major
> Labels: kip-848-client-support
> Fix For: 3.9.0
>
>
> If the new consumer is closed after sending a HB to join, but before
> receiving the response to it, it will send a leave group request but without
> member ID (will simply fail with UNKNOWN_MEMBER_ID). This will make that the
> broker will have a registered new member, for which it will never receive a
> leave request for it.
> # consumer.subscribe -> sends HB to join, transitions to JOINING
> # consumer.close -> will transition to LEAVING and send HB with epoch -1
> (without waiting for in-flight requests)
> # consumer receives response to initial HB, containing the assigned member
> ID. It will simply ignore it because it's not in the group anymore
> (UNSUBSCRIBED)
> Note that the expectation, with the current logic, and main downsides of this
> are:
> # If the case was that the member received partitions on the first HB, those
> partitions won't be re-assigned (broker waiting for the closed consumer to
> reconcile them), until the rebalance timeout expires.
> # Even if no partitions were assigned to it, the member will remain in the
> group from the broker point of view (but not from the client POV). The member
> will be eventually kicked out for not sending HBs, but only when it's session
> timeout expires.
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