@Override
  public List<RegionInfo> getAssignedRegions() {
    AssignmentManager am = services.getAssignmentManager();
    return am != null ? am.getAssignedRegions() : Collections.emptyList();
  }
Use to add balancer decision history to ring-buffer
hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/MasterClusterInfoProvider.java