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https://issues.apache.org/jira/browse/KAFKA-6794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16776694#comment-16776694
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Viktor Somogyi-Vass commented on KAFKA-6794:
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hey [~sql_consulting], thanks for sharing this. I think it is also a good
approach, and frankly now the only way one could incrementalize reassignments
manually. How would you make this queue? Do you have an algorithm for choosing
the next replica to drop and to add?
> 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: Viktor Somogyi-Vass
> 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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