code: protected SofaRouteException unavailableProviderException(String serviceKey, String providerInfo) {
          return new SofaRouteException(LogCodes.getLog(LogCodes.ERROR_TARGET_URL_INVALID, serviceKey, providerInfo));
      }
docs: 指定地址不可用
  
  @param serviceKey 服务关键字
  @return 服务端