function freezeUrl($url)
    {
        if (in_array($url, $this->frozen)) {
            return;
        }

        $client = new HttpKernel\Client($this->application);
        $client->request('GET', $url);

        $response = $client->getResponse();

        if (!$response->isOk()) {
            return;
        }

        $destination = $this->application['freezer.destination'] . $this->getFileName($url);

        if (!is_dir(dirname($destination))) {
            mkdir(dirname($destination), 0755, true);
        }

        file_put_contents($destination, $response->getContent());

        $this->frozen[] = $url;
    }