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https://issues.apache.org/jira/browse/HBASE-25739?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17380623#comment-17380623
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Hudson commented on HBASE-25739:
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Results for branch master
[build #343 on
builds.a.o|https://ci-hadoop.apache.org/job/HBase/job/HBase%20Nightly/job/master/343/]:
(x) *{color:red}-1 overall{color}*
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(/) {color:green}+1 general checks{color}
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(/) {color:green}+1 jdk8 hadoop3 checks{color}
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(/) {color:green}+1 source release artifact{color}
-- See build output for details.
(/) {color:green}+1 client integration test{color}
> TableSkewCostFunction need to use aggregated deviation
> ------------------------------------------------------
>
> Key: HBASE-25739
> URL: https://issues.apache.org/jira/browse/HBASE-25739
> Project: HBase
> Issue Type: Sub-task
> Components: Balancer, master
> Reporter: Clara Xiong
> Assignee: Clara Xiong
> Priority: Major
> Attachments:
> TEST-org.apache.hadoop.hbase.master.balancer.TestStochasticLoadBalancerBalanceCluster.xml,
>
> org.apache.hadoop.hbase.master.balancer.TestStochasticLoadBalancerBalanceCluster.txt
>
>
> TableSkewCostFunction uses the sum of the max deviation region per server for
> all tables as the measure of unevenness. It doesn't work in a very common
> scenario in operations. Say we have 100 regions on 50 nodes, two on each. We
> add 50 new nodes and they have 0 each. The max deviation from the mean is 1,
> compared to 99 in the worst case scenario of 100 regions on a single server.
> The normalized cost is 1/99 = 0.011 < default threshold of 0.05. Balancer
> wouldn't move. The proposal is to use aggregated deviation of the count per
> region server to detect this scenario, generating a cost of 100/198 = 0.5 in
> this case.
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