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Posted to dev@hbase.apache.org by "Duo Zhang (Jira)" <ji...@apache.org> on 2021/09/26 15:50:00 UTC
[jira] [Resolved] (HBASE-26297) Balancer run is improperly
triggered by accuracy error of double comparison
[ https://issues.apache.org/jira/browse/HBASE-26297?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Duo Zhang resolved HBASE-26297.
-------------------------------
Hadoop Flags: Reviewed
Resolution: Fixed
Pushed to branch-2.3+.
Thanks [~claraxiong] for contributing.
> Balancer run is improperly triggered by accuracy error of double comparison
> ---------------------------------------------------------------------------
>
> Key: HBASE-26297
> URL: https://issues.apache.org/jira/browse/HBASE-26297
> Project: HBase
> Issue Type: Bug
> Components: Balancer
> Environment: {code:java}
> {code}
> Reporter: Clara Xiong
> Assignee: Clara Xiong
> Priority: Major
> Fix For: 2.5.0, 3.0.0-alpha-2, 2.3.7, 2.4.7
>
>
> {code:java}
> protected synchronized boolean areSomeRegionReplicasColocated(Cluster c) {
> regionReplicaHostCostFunction.init(c);
> if (regionReplicaHostCostFunction.cost() > 0) {
> return true;
> }
> regionReplicaRackCostFunction.init(c);
> if (regionReplicaRackCostFunction.cost() > 0) {
> return true;
> }
> {code}
> The values are in double data type. Balancer could get stuck in constant runs and unnecessary moves.
> {code:java}
> 2021-09-24 12:02:41,943 INFO org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer: Running balancer because at least one server hosts replicas of the same region.
> 2021-09-24 12:01:42,878 INFO org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer: Finished computing new moving plan. Computation took 2400001 ms to try 3048341 different iterations. Found a solution that moves 81 regions; Going from a computed imbalance of 1.7429830473781883E-4 to a new imbalance of 1.6169961756947032E-4.
> {code}
> we should use COST_EPSILON instead of 0 for double comparison.
>
>
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