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https://issues.apache.org/jira/browse/HBASE-10498?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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rajeshbabu updated HBASE-10498:
-------------------------------

      Resolution: Fixed
    Hadoop Flags: Reviewed
          Status: Resolved  (was: Patch Available)

committed to trunk and 0.98.
Thank you all for reviews.

> 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: 0.98.1, 0.99.0
>
>         Attachments: HBASE-10498.patch
>
>
> 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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