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https://issues.apache.org/jira/browse/HBASE-25882?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xiaolin Ha updated HBASE-25882:
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Attachment: image-2021-08-17-20-20-12-768.png
> TableSkewCostFunction may cost unnecessary calculation steps when balancing
> by table
> ------------------------------------------------------------------------------------
>
> Key: HBASE-25882
> URL: https://issues.apache.org/jira/browse/HBASE-25882
> Project: HBase
> Issue Type: Improvement
> Components: Balancer
> Affects Versions: 3.0.0-alpha-1, 2.0.0
> Reporter: Xiaolin Ha
> Assignee: Xiaolin Ha
> Priority: Major
> Attachments: image-2021-08-17-20-20-12-768.png
>
>
> When using balance by table, the StochasticLoadBalancer will create the
> cluster state according to the regions distribution of only one table. As a
> result, the TableSkewCostFunction should be replaced by the
> RegionCountSkewCostFunction when the table count of the cluster state is less
> than 2.
> The most important problem is that, TableSkewCostFunction will cause
> unnecessary calculation steps when there is only one table. The cost it
> computed may be incorrect.
> For example, there are 5 online regionservers, and there is only one table
> with exactly one region, the cluster state is [0,0,0,0,1]. Then the cost of
> TableSkewCostFunction will be 1 (expect value is 0), because max=1, min=0.25,
> value=1. And the computedMaxSteps will be larger than 0, some balance actions
> will be generated to decrease the cost. But all the actions is meaningless
> for the skew count.
>
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