public int getRpcRefCount(BlockCacheKey cacheKey) {
    return (this.l2Cache instanceof BucketCache)
      ? ((BucketCache) this.l2Cache).getRpcRefCount(cacheKey)
      : 0;
  }
Returns the list of fully cached files
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/CombinedBlockCache.java