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Date: Tue, 24 Oct 2017 05:40:00 +0000 (UTC)
From: "ramkrishna.s.vasudevan (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-18946) Stochastic load balancer assigns
 replica regions to the same RS
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archived-at: Tue, 24 Oct 2017 05:40:08 -0000


    [ https://issues.apache.org/jira/browse/HBASE-18946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16216347#comment-16216347 ] 

ramkrishna.s.vasudevan commented on HBASE-18946:
------------------------------------------------

[~saint.ack@gmail.com] 
Thanks for the comment. Yes in a way I agree that fixing it in Balancer is best. But still in these cases the bulking mechanism is not a logical bulking instead it depends on the timed wait and the size of the queue. 
So the balancer may not really know what has been balanced by the time the next bulked set of region comes in. Any suggestions?
I can still check if it is possible to make balancer aware of this. But this mechanism solves some more issues in other related areas since we know the set of regions to be balanced at one shot.

> 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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