private void addTeritiaryAssignment(RegionInfo regionInfo, ServerName server) {
    // Process the region server to region map
    List<RegionInfo> regionList = teritiaryRSToRegionMap.get(server);
    if (regionList == null) {
      regionList = new ArrayList<>();
    }
    regionList.add(regionInfo);
    teritiaryRSToRegionMap.put(server, regionList);
  }
Initialize the region assignment snapshot by scanning the hbase:meta table
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/SnapshotOfRegionAssignmentFromMeta.java