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Posted to issues@hbase.apache.org by "Nick Dimiduk (Jira)" <ji...@apache.org> on 2021/04/14 16:21:00 UTC

[jira] [Assigned] (HBASE-25739) TableSkewCostFunction need to use aggregated deviation

     [ https://issues.apache.org/jira/browse/HBASE-25739?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nick Dimiduk reassigned HBASE-25739:
------------------------------------

    Assignee: Clara Xiong

> TableSkewCostFunction need to use aggregated deviation
> ------------------------------------------------------
>
>                 Key: HBASE-25739
>                 URL: https://issues.apache.org/jira/browse/HBASE-25739
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Balancer, master
>            Reporter: Clara Xiong
>            Assignee: Clara Xiong
>            Priority: Major
>
> TableSkewCostFunction uses the sum of the max deviation region per server for all tables as the measure of unevenness. It doesn't work in a very common scenario in operations. Say we have 100 regions on 50 nodes, two on each. We add 50 new nodes and they have 0 each. The max deviation from the mean is 1, compared to 99 in the worst case scenario of 100 regions on a single server. The normalized cost is 1/99 = 0.011 < default threshold of 0.05. Balancer wouldn't move.  The proposal is to use aggregated deviation of the count per region server to detect this scenario, generating a cost of 100/198 = 0.5 in this case.



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