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https://issues.apache.org/jira/browse/KAFKA-1792?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14258125#comment-14258125
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Dmitry Pekar commented on KAFKA-1792:
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[~nehanarkhede] Please see my answers:
1. This were negotiated requirements. Please talk about these changes with Joe
and I'll change the options in any required way.
2. If decision on 1. will take effect, I'll would certainly change my tests and
provide a result.
> 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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