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https://issues.apache.org/jira/browse/KAFKA-6794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16620507#comment-16620507
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Viktor Somogyi commented on KAFKA-6794:
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Hi [~smurakozi], are you working on this? In case you don't, I'd reassign this
to myself if you don't mind.
> Support for incremental replica reassignment
> --------------------------------------------
>
> Key: KAFKA-6794
> URL: https://issues.apache.org/jira/browse/KAFKA-6794
> Project: Kafka
> Issue Type: Improvement
> Reporter: Jason Gustafson
> Assignee: Sandor Murakozi
> Priority: Major
>
> Say you have a replication factor of 4 and you trigger a reassignment which
> moves all replicas to new brokers. Now 8 replicas are fetching at the same
> time which means you need to account for 8 times the current producer load
> plus the catch-up replication. To make matters worse, the replicas won't all
> become in-sync at the same time; in the worst case, you could have 7 replicas
> in-sync while one is still catching up. Currently, the old replicas won't be
> disabled until all new replicas are in-sync. This makes configuring the
> throttle tricky since ISR traffic is not subject to it.
> Rather than trying to bring all 4 new replicas online at the same time, a
> friendlier approach would be to do it incrementally: bring one replica
> online, bring it in-sync, then remove one of the old replicas. Repeat until
> all replicas have been changed. This would reduce the impact of a
> reassignment and make configuring the throttle easier at the cost of a slower
> overall reassignment.
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