class CachingSpaceUsageSource implements SpaceUsageSource {

  @Override
  public long getUsedSpace() {
    return cachedValue.get();
  }

  public  CachingSpaceUsageSource(SpaceUsageCheckParams params);
  @VisibleForTesting  CachingSpaceUsageSource(SpaceUsageCheckParams params,
      ScheduledExecutorService executor);

}