public function onRequestSent(Event $event)
    {
        $request = $event['request'];
        $response = $event['response'];
        $exception = $event['exception'];

        $params = $request->getParams();
        $retries = (int) $params->get(self::RETRY_PARAM);
        $delay = $this->strategy->getBackoffPeriod($retries, $request, $response, $exception);

        if ($delay !== false) {
            // Calculate how long to wait until the request should be retried
            $params->set(self::RETRY_PARAM, ++$retries)
                ->set(self::DELAY_PARAM, microtime(true) + $delay);
            // Send the request again
            $request->setState(RequestInterface::STATE_TRANSFER);
            $this->dispatch(self::RETRY_EVENT, array(
                'request'  => $request,
                'response' => $response,
                'handle'   => $exception ? $exception->getCurlHandle() : null,
                'retries'  => $retries,
                'delay'    => $delay
            ));
        }
    }