docs: public Object callManager(final Event event) {
          CommunicationException ex = null;
          Object object = null;
          for (int i = index; i < index + managerAddress.size(); i++) { // 循环一次manager的所有地址
              String address = managerAddress.get(i % managerAddress.size());
              try {
                  object = delegate.call(address, event);
                  index = i; // 更新一下上一次成功的地址
                  return object;
              } catch (CommunicationException e) {
                  // retry next address;
                  ex = e;
              }
          }
  
          throw ex; // 走到这一步，说明肯定有出错了
      }