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From "Heng Chen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15547) Balancer should take into account number of PENDING_OPEN regions
Date Wed, 30 Mar 2016 02:25:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15217267#comment-15217267

Heng Chen commented on HBASE-15547:

More generally I think the balancer should take into consideration a regionserver's inability
to serve regions.
Agree.  How to evaluate the RS inability? Yeah, "pending_open regions" is one factor.

> Balancer should take into account number of PENDING_OPEN regions
> ----------------------------------------------------------------
>                 Key: HBASE-15547
>                 URL: https://issues.apache.org/jira/browse/HBASE-15547
>             Project: HBase
>          Issue Type: Improvement
>          Components: Balancer, Operability, Region Assignment
>    Affects Versions: 0.98.0, 1.0.0
>            Reporter: Sean Busbey
>            Priority: Critical
>             Fix For: 2.0.0, 1.4.0
> We recently had a cluster get into a bad state where a subset of region servers consistently
could not open new regions (but could continue serving the regions they already hosted).
> Recovering the cluster was just a matter of restarting region servers in sequence. However,
this led to things getting substantially worse before they got better since the bulk assigner
continued to place an uniform number of recovered regions across all servers, including onto
those that could not open regions.
> It would be useful if the balancer could penalize regionservers with a backlog of pending_open
regions and place more work on those regionservers that are properly serving.

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