protected function _connection(array $config)
    {
        $redis = new \Redis;
        $host = empty($config['host']) ? self::DEFAULT_HOST : $config['host'];
        $port = empty($config['port']) ? self::DEFAULT_PORT : $config['port'];
        $timeout = empty($config['timeout']) ? self::DEFAULT_TIMEOUT : $config['timeout'];
        $connect = empty($config['persistent']) ? 'connect' : 'pconnect';
        $redis->$connect($host, $port, $timeout);
        return $redis;
    }