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https://issues.apache.org/jira/browse/HBASE-26872?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Xiaolin Ha updated HBASE-26872:
-------------------------------
Resolution: Fixed
Status: Resolved (was: Patch Available)
Merged to master and branch-2.4+, thanks [~bbeaudreault] and [~vjasani] for
reviewing!
> Load rate calculator for cost functions should be more precise
> --------------------------------------------------------------
>
> Key: HBASE-26872
> URL: https://issues.apache.org/jira/browse/HBASE-26872
> Project: HBase
> Issue Type: Improvement
> Components: Balancer
> Affects Versions: 2.4.11
> Reporter: Xiaolin Ha
> Assignee: Xiaolin Ha
> Priority: Major
> Fix For: 2.5.0, 3.0.0-alpha-3, 2.4.12
>
>
> The rate calculator should avoid negative values, e.g. if a region is moved
> from RS1 to RS2, the request count loads in the balancer cache maybe
> [100,200,0,100,200], then the region load cost calculated by
> CostFromRegionLoadAsRateFunction#getRegionLoadCost will be
> (100-200+100+100)/4=25, while the real cost is (100+0+100+200)/4=100.
> {code:java}
> protected double getRegionLoadCost(Collection<BalancerRegionLoad>
> regionLoadList) {
> Iterator<BalancerRegionLoad> iter = regionLoadList.iterator();
> if (!iter.hasNext()) {
> return 0;
> }
> double previous = getCostFromRl(iter.next());
> if (!iter.hasNext()) {
> return 0;
> }
> double cost = 0;
> do {
> double current = getCostFromRl(iter.next());
> cost += current - previous;
> previous = current;
> } while (iter.hasNext());
> return Math.max(0, cost / (regionLoadList.size() - 1));
> } {code}
> We should change the cost accumulate codes to,
> {code:java}
> cost += current >= previous ? current - previous : current; {code}
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