protected function getResponseFromChain(Chain $chain)
    {
        if (!$chain->getPlugins()) {
            throw $this->createNotFoundException('No any plugins');
        }

        $names = '';
        /* @var $plugin PluginInterface */
        foreach ($chain->getPlugins() as $plugin) {
            $names .= '|'.$plugin->getName();
        }

        return $this
            ->getCacheTimeKeeper()
            ->getResponse()
            ->setEtag(md5($names));
    }