[jira] [Created] (HBASE-26872) Load rate calculator for cost functions should be more precise

["Xiaolin Ha (Jira)" <ji...@apache.org>]

Xiaolin Ha created HBASE-26872:
----------------------------------

             Summary: 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


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+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}



--
This message was sent by Atlassian Jira
(v8.20.1#820001)