private function _responseFailHandle($error, $index)
    {
        $cbk = $this->requestList[$index]->getFailCallbackList();
        if (! empty($cbk)) {
            $error = array_reduce($cbk, function ($prev, $cb) {
                return $cb($prev);
            }, $error);
        }
        $response = new SimpleResponse();
        $response->setFail($error);
        $this->requestList[$index]->setResponse($response);
    }