code: public CounterSnapshot getCounterSnapshot(String counterId) throws IOException {
      final CounterSnapshot snapshot = inMemSnapshot.getIfPresent(counterId);
      if (snapshot != null) {
        stats.recordCounterCacheHit();
        return snapshot;
      }
      stats.recordCounterCacheMiss();
      return refreshCounterSnapshot(counterId);
    }
docs: Returns a recent snapshot, possibly read from inMemSnapshot.