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Posted to issues@hbase.apache.org by "Bryan Beaudreault (Jira)" <ji...@apache.org> on 2021/09/02 11:48:00 UTC

[jira] [Commented] (HBASE-26147) Add dry run mode to hbase balancer

    [ https://issues.apache.org/jira/browse/HBASE-26147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17408761#comment-17408761 ] 

Bryan Beaudreault commented on HBASE-26147:
-------------------------------------------

Yes, thank you Josh, Nick, Duo, Clara, and others. I appreciate all the help you gave in getting this landed

> Add dry run mode to hbase balancer
> ----------------------------------
>
>                 Key: HBASE-26147
>                 URL: https://issues.apache.org/jira/browse/HBASE-26147
>             Project: HBase
>          Issue Type: Improvement
>          Components: Balancer, master
>            Reporter: Bryan Beaudreault
>            Assignee: Bryan Beaudreault
>            Priority: Major
>             Fix For: 2.5.0, 3.0.0-alpha-2
>
>
> It's often rather hard to know how the cost function changes you're making will affect the balance of the cluster, and currently the only way to know is to run it. If the cost decisions are not good, you may have just moved many regions towards a non-ideal balance. Region moves themselves are not free for clients, and the resulting balance may cause a regression.
> We should add a mode to the balancer so that it can be invoked without actually executing any plans. This will allow an administrator to iterate on their cost functions and used the balancer's logging to see how their changes would affect the cluster. 



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