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https://issues.apache.org/jira/browse/HBASE-26023?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Duo Zhang reopened HBASE-26023:
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> tableSkewCostFunction aggregate cost per table incorrectly
> ----------------------------------------------------------
>
> Key: HBASE-26023
> URL: https://issues.apache.org/jira/browse/HBASE-26023
> Project: HBase
> Issue Type: Sub-task
> Components: Balancer, test
> Reporter: Clara Xiong
> Priority: Major
> Fix For: 3.0.0-alpha-1, 2.3.6, 2.4.5
>
>
> There is another bug in the original tableSkew cost function for aggregation
> of the cost per table:
> If we have 10 regions, one per table, evenly distributed on 10 nodes, the
> cost is scale to 1.0.
> The more tables we have, the closer the value will be to 1.0. The cost
> function becomes useless.
> All the balancer tests were set up with large numbers of tables with minimal
> regions per table. This artificially inflates the total cost and trigger
> balancer runs. With this fix on TableSkewFunction, we need to overhaul the
> tests too. We also need to add tests that reflect more diversified scenarios
> for table distribution such as large tables with large numbers of regions.
> {code:java}
> protected double cost() {
> double max = cluster.numRegions;
> double min = ((double) cluster.numRegions) / cluster.numServers;
> double value = 0;
> for (int i = 0; i < cluster.numMaxRegionsPerTable.length; i++) {
> value += cluster.numMaxRegionsPerTable[i];
> }
> LOG.info("min = {}, max = {}, cost= {}", min, max, value);
> return scale(min, max, value);
> }
> }{code}
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