public void unlock(QuotaResource quotaResource) {
    ReentrantLock lock = quotaResourceMutexCache.mutexCache.getOrDefault(quotaResource, null);
    if (lock != null) {
      lock.unlock();
    } else {
      LOGGER.warn("Attempted unlock for {} when lock wasn't held.", quotaResource);
      quotaMetrics.quotaResourceInvalidUnlockAttemptCount.inc();
    }
  }
Releases the lock for the quota resource represented by the specified {@link QuotaResource}.
@param quotaResource {@link QuotaResource} object representing the quota resource for which lock needs to be
                     released.
ambry-quota/src/main/java/com/github/ambry/quota/QuotaResourceSynchronizer.java