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From "Ted Yu (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3373) Allow regions of specific table to be load-balanced
Date Wed, 30 Nov 2011 18:57:40 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13160233#comment-13160233
] 

Ted Yu commented on HBASE-3373:
-------------------------------

@Ben:
Thanks for trying out 0.94

The code snippet above deals with region server which recently joined the cluster. Its goal
is to avoid hot region server which receives above average load.
This is part of the changes from HBASE-3609. The randomization is done on this line:
{code}
    Collections.shuffle(sns, RANDOM);
{code}
where we schedule regions to region servers which are shuffled randomly.

Your observation about unbalanced table(s) in the cluster is valid. This is due to master
not passing per-table region distribution to balanceCluster().
I have a patch which is in internal repository where master calls balanceCluster() for each
table.
Once we test it in production cluster, I should be able to contribute back.
                
> Allow regions of specific table to be load-balanced
> ---------------------------------------------------
>
>                 Key: HBASE-3373
>                 URL: https://issues.apache.org/jira/browse/HBASE-3373
>             Project: HBase
>          Issue Type: Improvement
>          Components: master
>    Affects Versions: 0.20.6
>            Reporter: Ted Yu
>         Attachments: HbaseBalancerTest2.java
>
>
> From our experience, cluster can be well balanced and yet, one table's regions may be
badly concentrated on few region servers.
> For example, one table has 839 regions (380 regions at time of table creation) out of
which 202 are on one server.
> It would be desirable for load balancer to distribute regions for specified tables evenly
across the cluster. Each of such tables has number of regions many times the cluster size.

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