public List<RSGroupInfo> listRSGroups() throws IOException {
    try {
      List<RSGroupProtos.RSGroupInfo> resp = stub
        .listRSGroupInfos(null, ListRSGroupInfosRequest.getDefaultInstance()).getRSGroupInfoList();
      List<RSGroupInfo> result = new ArrayList<>(resp.size());
      for (RSGroupProtos.RSGroupInfo entry : resp) {
        result.add(ProtobufUtil.toGroupInfo(entry));
      }
      return result;
    } catch (ServiceException e) {
      throw ProtobufUtil.handleRemoteException(e);
    }
  }
Lists current set of RegionServer groups.
hbase-server/src/main/java/org/apache/hadoop/hbase/rsgroup/RSGroupAdminClient.java