MatthiasMullie\Scrapbook\Scale\StampedeProtector::protect PHP Method

    protected function protect(array $keys)
    {
        if (empty($keys)) {
            return array();
        }
        $success = array();
        foreach ($keys as $key) {
            /*
             * Key is add()ed because there may be multiple concurrent processes
             * that are both in the process of protecting - first one to add()
             * wins (and those are returned by the function, so those that are
             * failed to protect can be considered protected)
             */
            $success[$key] = $this->cache->add($this->stampedeKey($key), '', $this->sla);
        }
        return array_keys(array_filter($success));
    }