public function onBeforeSend(Event $event)
    {
        /** @var \Guzzle\Http\Message\Request $request */
        $request = $event['request'];

        list($newUrl, $port) = $this->proxify(
            $request->getUrl(),
            $this->bucketKey,
            $this->gatewayHost
        );

        $request->setUrl($newUrl);

        if ($port) {
            $request->setHeader('Runscope-Request-Port', $port);
        }

        if ($this->authToken) {
            $request->setHeader('Runscope-Bucket-Auth', $this->authToken);
        }
    }