private synchronized void updateDefaultServers() {
    LOG.info("Updating default servers.");
    Map<String, RSGroupInfo> newGroupMap = Maps.newHashMap(holder.groupName2Group);
    RSGroupInfo oldDefaultGroupInfo = getRSGroup(RSGroupInfo.DEFAULT_GROUP);
    assert oldDefaultGroupInfo != null;
    RSGroupInfo newDefaultGroupInfo =
      new RSGroupInfo(RSGroupInfo.DEFAULT_GROUP, getDefaultServers());
    newDefaultGroupInfo.addAllTables(oldDefaultGroupInfo.getTables());
    newGroupMap.put(RSGroupInfo.DEFAULT_GROUP, newDefaultGroupInfo);
    // do not need to persist, as we do not persist default group.
    resetRSGroupMap(newGroupMap);
    LOG.info("Updated default servers, {} servers", newDefaultGroupInfo.getServers().size());
    if (LOG.isDebugEnabled()) {
      LOG.debug("New default servers list: {}", newDefaultGroupInfo.getServers());
    }
  }
Table descriptor for <code>hbase:rsgroup</code> catalog table
hbase-server/src/main/java/org/apache/hadoop/hbase/rsgroup/RSGroupInfoManagerImpl.java