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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3609) Improve the selection of regions to balance; part 2
Date Tue, 12 Apr 2011 06:05:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13018735#comment-13018735

Ted Yu commented on HBASE-3609:

For unit test, the region Ids created by mockClusterServers() have the same value - because
all the regions are created at almost the same time.
It will take a little more time to devise appropriate test case generation and validate the
balancing moves.

For the moment, I still base my improvement on the existing framework where region count plays
dominant factor.

One of the goals of this JIRA is to remove randomness from LoadBalancer so that we can deterministically
produce near-optimal balancing actions.
The new parameter, emptyRegionServerPresent, helps decide whether we should move old and new
regions to other servers.

I will upload a new patch where I describe the above in detail. I even plan to blog about
the history of HBASE-3586 and this JIRA.

To validate my latest patch, I need a little help from community participants. Our use case
creates hbase tables frequently in our flow with pre-split regions. Since those regions get
round-robin assigned initially, it is not easy to reproduce what Stan experienced.

Thanks for the review and suggestion, Stack.

> Improve the selection of regions to balance; part 2
> ---------------------------------------------------
>                 Key: HBASE-3609
>                 URL: https://issues.apache.org/jira/browse/HBASE-3609
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: stack
>            Assignee: Ted Yu
>         Attachments: 3609-alternate.txt, 3609-empty-RS.txt, hbase-3609-by-region-age.txt,
> See 'HBASE-3586  Improve the selection of regions to balance' for discussion of algorithms
that improve on current random assignment.

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