public synchronized void addServer(RegionInfo regionInfo, ServerName serverName) {
    OnlineEntry rse = new OnlineEntry(regionInfo, serverName);
    this.deployedEntries.add(rse);
    this.deployedOn.add(serverName);
    // save the replicaId that we see deployed in the cluster
    this.deployedReplicaId = regionInfo.getReplicaId();
    this.primaryHRIForDeployedReplica =
      RegionReplicaUtil.getRegionInfoForDefaultReplica(regionInfo);
  }
Maintain information about a particular region. It gathers information from three places -- HDFS,
META, and region servers.
hbase-server/src/main/java/org/apache/hadoop/hbase/util/HbckRegionInfo.java