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Date: Tue, 11 Feb 2014 17:15:19 +0000 (UTC)
From: "James Taylor (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12694457.1392114369340.24589.1392138919553@arcas>
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Subject: [jira] [Commented] (HBASE-10498) Add new APIs to load balancer
 interface
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    [ https://issues.apache.org/jira/browse/HBASE-10498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13898035#comment-13898035 ] 

James Taylor commented on HBASE-10498:
--------------------------------------

Can this work be done in 0.98?

> Add new APIs to load balancer interface
> ---------------------------------------
>
>                 Key: HBASE-10498
>                 URL: https://issues.apache.org/jira/browse/HBASE-10498
>             Project: HBase
>          Issue Type: Improvement
>          Components: Balancer
>            Reporter: rajeshbabu
>            Assignee: rajeshbabu
>             Fix For: 0.99.0
>
>
> If a custom load balancer required to maintain region and corresponding server locations,
> we can capture this information when we run any balancer algorithm before assignment(like random,retain).
> But during master startup we will not call any balancer algorithm if a region already assinged
> During split also we open child regions first in RS and then notify to master through zookeeper. 
> So split regions information cannot be captured into balancer.
> Since balancer has access to master we can get the information from online regions or region plan data structures in AM.
> But some use cases we cannot relay on this information(mainly to maintain colocation of two tables regions). 
> So it's better to add some APIs to load balancer to notify balancer when *region is online or offline*.
> These APIs helps a lot to maintain *regions colocation through custom load balancer* which is very important in secondary indexing. 


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