public function key($reset = false)
    {
        static $key;
        $key = $reset ? false : $key;
        if (!$key) {
            $key = $this->instance->get('memcached_adapter_namespace', function ($memc, $key, &$value) {
                $value = bin2hex(openssl_random_pseudo_bytes(8));
                return true;
            });
        }
        return $key;
    }