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https://issues.apache.org/jira/browse/KAFKA-17116?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17869982#comment-17869982
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Kirk True commented on KAFKA-17116:
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{color:#172b4d}For the sake of discussion, if we were to consciously ignore
this case for now (and let the broker reassign the partitions after the
timeout), do we have a sense of the actual impact to the user? I'm wondering if
this is an optimization that we can save for when we have empirical evidence to
justify a specialized fix?{color}
> 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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