public void addRegionToServer(final RegionStateNode regionNode) {
    ServerStateNode serverNode = getServerNode(regionNode.getRegionLocation());
    serverNode.addRegion(regionNode);
  }
Returns Pertinent ServerStateNode or NULL if none found (Do not make modifications).
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/RegionStates.java