class CacheCollectorHelper

class CacheCollectorHelper extends CacheCollector {
    
    /**
     * Contains data to return on a cache miss.
     * @var array
     */
    protected $cacheMissData = [];
    
    /**
     * Number of calls to \Drupal\Core\Cache\CacheCollector::resolveCacheMiss().
     *
     * @var int
     */
    protected $cacheMisses = 0;
    
    /**
     * {@inheritdoc}
     */
    public function set($key, $value) {
        parent::set($key, $value);
        $this->persist($key);
    }
    
    /**
     * {@inheritdoc}
     */
    public function resolveCacheMiss($key) {
        $this->cacheMisses++;
        if (isset($this->cacheMissData[$key])) {
            $this->storage[$key] = $this->cacheMissData[$key];
            $this->persist($key);
            return $this->cacheMissData[$key];
        }
    }
    
    /**
     * Sets data to return from a cache miss resolve.
     *
     * @param string $key
     *   The key being looked for.
     * @param mixed $value
     *   The value to return.
     */
    public function setCacheMissData($key, $value) {
        $this->cacheMissData[$key] = $value;
    }
    
    /**
     * Returns the number of cache misses.
     *
     * @return int
     *   Number of calls to the resolve cache miss method.
     */
    public function getCacheMisses() {
        return $this->cacheMisses;
    }

}