Make region balancing sloppier
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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:
{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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