[jira] Resolved: (HBASE-920) Make region balancing sloppier

["stack (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-920?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

stack resolved HBASE-920.
-------------------------

       Resolution: Fixed
    Fix Version/s: 0.19.0

Committed branch and trunk

> Make region balancing sloppier
> ------------------------------
>
>                 Key: HBASE-920
>                 URL: https://issues.apache.org/jira/browse/HBASE-920
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: stack
>            Assignee: stack
>             Fix For: 0.18.1, 0.19.0
>
>         Attachments: hbase-920.patch
>
>
> The region load balancer is exacting.  Here's the logic:
> {code}
>         if (avgLoad > 2.0 && thisServersLoad.getNumberOfRegions() > avgLoad) {
>           if (LOG.isDebugEnabled()) {
>             LOG.debug("Server " + serverName + " is overloaded. Server load: " +
>               thisServersLoad.getNumberOfRegions() + " avg: " + avgLoad);
>           }
> ...
> {code}
> On a cluster of thousands of regions, especially around startup or if there's been a crash, the above makes for a bunch of churn as load balancer closes and opens nodes to achieve an exact balance (all nodes must be <= to average).
> I'd suggest that nodes should be left alone if they are within some percentage of the average -- say 10% (should be configurable).

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