@Override
  public List<ServerName> getOnlineServersListWithPredicator(List<ServerName> servers,
    Predicate<ServerMetrics> filter) {
    ServerManager sm = services.getServerManager();
    return sm != null
      ? sm.getOnlineServersListWithPredicator(servers, filter)
      : Collections.emptyList();
  }
Use to add balancer decision history to ring-buffer
hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/MasterClusterInfoProvider.java