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https://issues.apache.org/jira/browse/KAFKA-1792?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14260494#comment-14260494
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Neha Narkhede commented on KAFKA-1792:
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[~Dmitry Pekar] Since this is a user facing change, it will help to be precise
about the use cases and describe the user interaction for each use case. Think
of this being useful while updating our docs (which we should just do before
closing this out). Removing --generate makes a lot of sense with your patch.
Adding --rebalance also makes sense. I'll help a lot for you to walk through
the uses cases and interaction though.
> change behavior of --generate to produce assignment config with fair replica
> distribution and minimal number of reassignments
> -----------------------------------------------------------------------------------------------------------------------------
>
> Key: KAFKA-1792
> URL: https://issues.apache.org/jira/browse/KAFKA-1792
> Project: Kafka
> Issue Type: Sub-task
> Components: tools
> Reporter: Dmitry Pekar
> Assignee: Dmitry Pekar
> Fix For: 0.8.3
>
> Attachments: KAFKA-1792.patch, KAFKA-1792_2014-12-03_19:24:56.patch,
> KAFKA-1792_2014-12-08_13:42:43.patch, KAFKA-1792_2014-12-19_16:48:12.patch,
> generate_alg_tests.txt
>
>
> Current implementation produces fair replica distribution between specified
> list of brokers. Unfortunately, it doesn't take
> into account current replica assignment.
> So if we have, for instance, 3 brokers id=[0..2] and are going to add fourth
> broker id=3,
> generate will create an assignment config which will redistribute replicas
> fairly across brokers [0..3]
> in the same way as those partitions were created from scratch. It will not
> take into consideration current replica
> assignment and accordingly will not try to minimize number of replica moves
> between brokers.
> As proposed by [~charmalloc] this should be improved. New output of improved
> --generate algorithm should suite following requirements:
> - fairness of replica distribution - every broker will have R or R+1 replicas
> assigned;
> - minimum of reassignments - number of replica moves between brokers will be
> minimal;
> Example.
> Consider following replica distribution per brokers [0..3] (we just added
> brokers 2 and 3):
> - broker - 0, 1, 2, 3
> - replicas - 7, 6, 0, 0
> The new algorithm will produce following assignment:
> - broker - 0, 1, 2, 3
> - replicas - 4, 3, 3, 3
> - moves - -3, -3, +3, +3
> It will be fair and number of moves will be 6, which is minimal for specified
> initial distribution.
> The scope of this issue is:
> - design an algorithm matching the above requirements;
> - implement this algorithm and unit tests;
> - test it manually using different initial assignments;
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