[jira] [Created] (HBASE-26297) Balancer run is improperly triggered by accuracy error of double comparison

["Clara Xiong (Jira)" <ji...@apache.org>]

Clara Xiong created HBASE-26297:
-----------------------------------

             Summary: 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


{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. we often run into unnecessary runs.
{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}
As in another PR, we should use a delta minimum value instead of 0 for double comparison.

 

 



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