private void updateAssignmentManagerMetrics() {
    services.getAssignmentManager().getAssignmentManagerMetrics()
      .updateHoles(lastReport.getHoles().size());
    services.getAssignmentManager().getAssignmentManagerMetrics()
      .updateOverlaps(lastReport.getOverlaps().size());
    services.getAssignmentManager().getAssignmentManagerMetrics()
      .updateUnknownServerRegions(lastReport.getUnknownServers().size());
    services.getAssignmentManager().getAssignmentManagerMetrics()
      .updateEmptyRegionInfoRegions(lastReport.getEmptyRegionInfo().size());
  }
Checks if a region still holds references to parent.
@param tableName The table for the region
@param region    The region to check
@return A pair where the first boolean says whether the region directory exists in the
        filesystem and then the second boolean says whether the region has references to a
        parent.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/janitor/CatalogJanitor.java