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https://issues.apache.org/jira/browse/KAFKA-8420?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Matthew de Detrich reassigned KAFKA-8420:
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Assignee: Matthew de Detrich
> Graceful handling when consumer switches from subscribe to manual assign
> ------------------------------------------------------------------------
>
> Key: KAFKA-8420
> URL: https://issues.apache.org/jira/browse/KAFKA-8420
> Project: Kafka
> Issue Type: Improvement
> Components: consumer
> Reporter: Guozhang Wang
> Assignee: Matthew de Detrich
> Priority: Major
>
> Today if a consumer switches between subscribe (and hence relies on group
> rebalance to get assignment) and manual assign, it may cause unnecessary
> rebalances. For example:
> 1. consumer.subscribe();
> 2. consumer.poll(); // join-group request sent, returns empty because
> poll timeout
> 3. consumer.unsubscribe();
> 4. consumer.assign(..);
> 5. consumer.poll(); // sync-group request received, and the assigned
> partitions does not match the current subscription-state. In this case it
> will tries to re-join which is not necessary.
> In the worst case (i.e. leader keep sending incompatible assignment), this
> would case the consumer to fall into endless re-joins.
> Although it is not a very common usage scenario, it still worth being better
> handled than the status-quo.
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