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https://issues.apache.org/jira/browse/HBASE-3679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13009469#comment-13009469
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Ted Yu commented on HBASE-3679:
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>From Jonathan:
One of the hardest parts of load balancing based on request count and other
dynamic/transient measures is that you can get some pretty pathological
conditions where you are always moving stuff around.
To guard against it, I think we'll need to move to more of a cost-based
algorithm that is taking not just the difference in request counts into account
but also a baseline "cost" of moving a region. The cost difference in load
between two unbalanced servers would have to outweigh the cost associated with
moving a region. As you say, looking at the number of live operations to a
given region could contribute to the cost of moving that region, but the best
measure for that is probably just looking at request count (it's all requests
that incur a cost, not just active scanners).
> Provide cost information associated with moving region(s)
> ---------------------------------------------------------
>
> Key: HBASE-3679
> URL: https://issues.apache.org/jira/browse/HBASE-3679
> Project: HBase
> Issue Type: Improvement
> Reporter: Ted Yu
>
> In order for load balancer to make better decision, we need to establish cost
> model for moving region(s).
> One factor would be the number of active scanners on a particular region.
> This count is easy to maintain at HRegion level. instantiateInternalScanner()
> can increment the counter and RegionScanner.close() would decrement the count.
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