Guanghao Zhang created HBASE-23078:
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             Summary: BaseLoadBalancer should consider region replicas when 
randomAssignment and roundRobinAssignment
                 Key: HBASE-23078
                 URL: https://issues.apache.org/jira/browse/HBASE-23078
             Project: HBase
          Issue Type: Task
            Reporter: Guanghao Zhang


Copied the comment in HBASE-23035.

 

There are two problems about the LoadBalancer.

 

1. The cluster means the cluster state of the whole cluster. But 
hasRegionReplica is false, so it only create clusterstate by the regions which 
need to assign, not the whole cluster...
{code:java}
Cluster cluster = createCluster(servers, regions, false);
List<RegionInfo> unassignedRegions = new ArrayList<>();
roundRobinAssignment(cluster, regions, unassignedRegions,
  servers, assignments);


  protected Cluster createCluster(List<ServerName> servers, 
Collection<RegionInfo> regions,
      boolean hasRegionReplica) {
    // Get the snapshot of the current assignments for the regions in question, 
and then create
    // a cluster out of it. Note that we might have replicas already assigned 
to some servers
    // earlier. So we want to get the snapshot to see those assignments, but 
this will only contain
    // replicas of the regions that are passed (for performance).
    Map<ServerName, List<RegionInfo>> clusterState = null;
    if (!hasRegionReplica) {
      clusterState = getRegionAssignmentsByServer(regions);
    } else {
      // for the case where we have region replica it is better we get the 
entire cluster's snapshot
      clusterState = getRegionAssignmentsByServer(null);
    }    for (ServerName server : servers) {
      if (!clusterState.containsKey(server)) {
        clusterState.put(server, EMPTY_REGION_LIST);
      }
    }
    return new Cluster(regions, clusterState, null, this.regionFinder,
        rackManager);
  }
{code}
2. wouldLowerAvailability method only consider the primary regions. The replica 
region can't assign to same server with primary region. But can be assigned to 
same server with other replica regions.



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