@Override
  public List<RSGroupInfo> listRSGroups() throws IOException {
    return Arrays.asList(new RSGroupInfo(RSGroupInfo.DEFAULT_GROUP, getOnlineServers()));
  }
A dummy RSGroupInfoManager which only contains a default rs group.
hbase-server/src/main/java/org/apache/hadoop/hbase/rsgroup/DisabledRSGroupInfoManager.java