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https://issues.apache.org/jira/browse/HBASE-13376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14549554#comment-14549554
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Ted Yu commented on HBASE-13376:
--------------------------------
{code}
771 private Comparator<Integer> localityComparator = new
Comparator<Integer>() {
772 @Override
773 public int compare(Integer integer, Integer integer2) {
{code}
Can the parameters for compare() have better names, such as server1, server2 ?
{code}
794 while (localityPerServer[lowestLocalServerIndex] == 0
795 && (regionsPerServer[lowestLocalServerIndex].length == 0)) {
{code}
The above assumes 0 is the lowest locality. What if locality for
serverIndicesSortedByLocality[0] is greater than 0 but the region count on the
server is 0 ?
{code}
796 i++;
797 lowestLocalServerIndex = serverIndicesSortedByLocality[i];
{code}
Better check for boundary before assigning lowestLocalServerIndex.
Test failure in TestRegionRebalancing might be related to patch, however
https://builds.apache.org/job/PreCommit-HBASE-Build/13602//testReport/ is no
longer accessible.
> Improvements to Stochastic load balancer
> ----------------------------------------
>
> Key: HBASE-13376
> URL: https://issues.apache.org/jira/browse/HBASE-13376
> Project: HBase
> Issue Type: Improvement
> Components: Balancer
> Affects Versions: 1.0.0, 0.98.12
> Reporter: Vandana Ayyalasomayajula
> Assignee: Vandana Ayyalasomayajula
> Priority: Minor
> Attachments: HBASE-13376_0.98.txt, HBASE-13376_0.txt,
> HBASE-13376_98.patch
>
>
> There are two things this jira tries to address:
> 1. The locality picker in the stochastic balancer does not pick regions with
> least locality as candidates for swap/move. So when any user configures
> locality cost in the configs, the balancer does not always seems to move
> regions with bad locality.
> 2. When a cluster has equal number of loaded regions, it always picks the
> first one. It should pick a random region on one of the equally loaded
> servers. This improves a chance of finding a good candidate, when load picker
> is invoked several times.
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