apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/component/RetryableRestTemplate.java/RetryableRestTemplate/getAdminServices
class RetryableRestTemplate:  private List<ServiceDTO> getAdminServices(Env env, Transaction ct) {

    List<ServiceDTO> services = adminServiceAddressLocator.getServiceList(env);

    if (CollectionUtils.isEmpty(services)) {
      ServiceException e = new ServiceException(String.format("No available admin server."
                                                              + " Maybe because of meta server down or all admin server down. "
                                                              + "Meta server address: %s",
              portalMetaDomainService.getDomain(env)));
      ct.setStatus(e);
      ct.complete();
      throw e;
    }

    return services;
  }