@Override
  public MasterProtos.BalanceResponse balance(RpcController controller,
    MasterProtos.BalanceRequest request) throws ServiceException {
    try {
      return ProtobufUtil.toBalanceResponse(server.balance(ProtobufUtil.toBalanceRequest(request)));
    } catch (IOException ex) {
      throw new ServiceException(ex);
    }
  }
Returns list of blocking services and their security info classes that this server supports
hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterRpcServices.java