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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10528) DefaultBalancer selects plans to move regions onto draining nodes
Date Thu, 15 Jan 2015 19:04:35 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10528?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14279112#comment-14279112
] 

Hudson commented on HBASE-10528:
--------------------------------

SUCCESS: Integrated in HBase-0.94-security #569 (See [https://builds.apache.org/job/HBase-0.94-security/569/])
HBASE-10528 DefaultBalancer selects plans to move regions onto draining nodes. (churro morales)
(larsh: rev 1f0f62ced826189bf9dbfcee2247d89b4d90b0e3)
* src/test/java/org/apache/hadoop/hbase/master/TestAssignmentManager.java
* src/main/java/org/apache/hadoop/hbase/master/AssignmentManager.java


> DefaultBalancer selects plans to move regions onto draining nodes
> -----------------------------------------------------------------
>
>                 Key: HBASE-10528
>                 URL: https://issues.apache.org/jira/browse/HBASE-10528
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.94.5
>            Reporter: churro morales
>            Assignee: churro morales
>             Fix For: 1.0.0, 2.0.0, 0.98.10, 1.1.0
>
>         Attachments: 10528-1.0.addendum, HBASE-10528-0.94.patch, HBASE-10528-0.98.patch,
HBASE-10528-0.98.v2.patch, HBASE-10528.patch, HBASE-10528.v2.patch
>
>
> We have quite a large cluster > 100k regions, and we needed to isolate a region was
very hot until we could push a patch.  We put this region on its own regionserver and set
it in the draining state.  The default balancer was selecting regions to move to this cluster
for its region plans.  
> It just so happened for other tables, the default load balancer was creating plans for
the draining servers, even though they were not available to move regions to.  Thus we were
closing regions, then attempting to move them to the draining server then finding out its
draining. 
> We had to disable the balancer to resolve this issue.
> There are some approaches we can take here.
> 1. Exclude draining servers altogether, don't even pass those into the load balancer
from HMaster.
> 2. We could exclude draining servers from ceiling and floor calculations where we could
potentially skip load balancing because those draining servers wont be represented when deciding
whether to balance.
> 3. Along with #2 when assigning regions, we would skip plans to assign regions to those
draining servers.
> I am in favor of #1 which is simply removes servers as candidates for balancing if they
are in the draining state.
> But I would love to hear what everyone else thinks.



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