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https://issues.apache.org/jira/browse/HBASE-3679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13022327#comment-13022327
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Ted Yu commented on HBASE-3679:
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>From Stack:
I think the next step would be adding more smarts to balancer so it
could make calls on how loaded a regionserver was and so it had an
idea of how long a region had been open on a particular regionserver.
Anything that was open < 5 minutes or so would not be moved.
Something like that. If a regionserver is taking lots of load, move a
selection of regions to the least loaded.
Stack's comment from HBASE-3799:
A general comment on balancing (that probably fits better elsewhere than as a
comment on this issue) is that we need 'smoothing' of region move.... Yesterday
we brought a regionserver back online into a smallish cluster that was under
load and the balance run unloaded a bunch of regions all in the one go which
put a dent in the throughput; it'd be sweet if the balancer ran at an
appropriate 'rate'. When under load, it should move regions 'gently' rather
than all as a big bang (the decommission script will move a region at a time,
verifying it deployed in its new location before moving another... this can
take ages to complete but its proven minimally disruptive to loadings)
> 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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