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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18946) Stochastic load balancer assigns replica regions to the same RS
Date Thu, 19 Oct 2017 09:28:01 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16210767#comment-16210767

ramkrishna.s.vasudevan commented on HBASE-18946:

bq.Do we need to apply the same collection logic to EnableTableProcedure (to address the TODO
in the comment)? 
Yes it could be. But with HBASE-19017 it may not be needed because we know where the assignment
would go.
But before I commit this I would like to spend some more time to understand if there could
be any other issues with how the procedure pool executes and we could starve other threads
from adding to the assignQueue and only the other threads keep retrying which I think happened
when I tried doing the same for enableTablePRocedure. But HBASE-19017 we are safe. 
And thanks a lot for the review [~huaxiang].

> Stochastic load balancer assigns replica regions to the same RS
> ---------------------------------------------------------------
>                 Key: HBASE-18946
>                 URL: https://issues.apache.org/jira/browse/HBASE-18946
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 2.0.0-alpha-3
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 2.0.0-beta-1
>         Attachments: HBASE-18946.patch, HBASE-18946.patch, TestRegionReplicasWithRestartScenarios.java
> Trying out region replica and its assignment I can see that some times the default LB
Stocahstic load balancer assigns replica regions to the same RS. This happens when we have
3 RS checked in and we have a table with 3 replicas. When a RS goes down then the replicas
being assigned to same RS is acceptable but the case when we have enough RS to assign this
behaviour is undesirable and does not solve the purpose of replicas. 
> [~huaxiang] and [~enis]. 

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