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https://issues.apache.org/jira/browse/HBASE-16958?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gary Helmling resolved HBASE-16958.
-----------------------------------
Resolution: Duplicate
Assignee: (was: Gary Helmling)
Fix Version/s: (was: 1.3.0)
I re-opened HBASE-16570 to fix the issue that is described here.
> Balancer recomputes block distributions every time balanceCluster() runs
> ------------------------------------------------------------------------
>
> Key: HBASE-16958
> URL: https://issues.apache.org/jira/browse/HBASE-16958
> Project: HBase
> Issue Type: Bug
> Components: Balancer
> Reporter: Gary Helmling
>
> The change in HBASE-16570 modified the balancer to compute block
> distributions in parallel with a pool of 5 threads. However, because it does
> this every time Cluster is instantiated, it effectively bypasses the cache of
> block locations added in HBASE-14473:
> In the LoadBalancer.balanceCluster() implementations (in
> StochasticLoadBalancer, SimpleLoadBalancer), we create a new Cluster instance.
> In Cluster.<init>, we call registerRegion() on every HRegionInfo.
> In registerRegion(), we do the following:
> {code}
> regionLocationFutures.set(regionIndex,
> regionFinder.asyncGetBlockDistribution(region));
> {code}
> Then, back in Cluster.<init> we do a get() on each ListenableFuture in a loop.
> So while we are doing the calls to get block locations in parallel with 5
> threads, we're recomputing them every time balanceCluster() is called and not
> taking advantage of the cache at all.
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