private function newMemcachedServers(Memcached $memcached, array $servers)
    {
        $serverIndex = [];
        $existingServers = $memcached->getServerList();

        foreach ($existingServers as $server) {
            $serverIndex[$server['host'] . ':' . $server['port']] = true;
        }

        foreach ($servers as $configServer) {
            $server = [
                'host' => array_get($configServer, 'host', ''),
                'port' => array_get($configServer, 'port', 11211),
                'weight' => array_get($configServer, 'weight', 0),
            ];

            if (!isset($serverIndex[$server['host'] . ':' . $server['port']])) {
                yield $server;
            }
        }
    }