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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-920) Make region balancing sloppier
Date Sat, 11 Oct 2008 05:30:47 GMT
Make region balancing sloppier

                 Key: HBASE-920
                 URL: https://issues.apache.org/jira/browse/HBASE-920
             Project: Hadoop HBase
          Issue Type: Improvement
            Reporter: stack

The region load balancer is exacting.  Here's the logic:

        if (avgLoad > 2.0 && thisServersLoad.getNumberOfRegions() > avgLoad)
          if (LOG.isDebugEnabled()) {
            LOG.debug("Server " + serverName + " is overloaded. Server load: " +
              thisServersLoad.getNumberOfRegions() + " avg: " + avgLoad);

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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