@Override
  public AmbryCacheEntry getObject(String key) {
    AmbryCacheEntry ambryCacheEntry = super.getObject(key);
    if (ambryCacheEntry != null) {
      cacheHitCountDown.countDown();
    } else {
      cacheMissCountDown.countDown();
    }
    return ambryCacheEntry;
  }
Constructs an instance of AmbryCache
@param cacheId String identifier for this cache
@param cacheEnabled Toggles cache. If true, cache is enabled. Else, cache is disabled.
@param maxNumCacheEntries Maximum number of cache entries
@param metricRegistry Instance of metrics registry to record stats
ambry-router/src/test/java/com/github/ambry/router/AmbryCacheWithStats.java