[HBASE-26105] Rectify the expired TODO comment in CombinedBC

• Type: Improvement
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: 2.5.0, 3.0.0-alpha-2, 2.4.6, 2.3.7
• Component/s: BlockCache
• Hadoop Flags: Reviewed
• Assignee: Yutong Xiao
• Reporter: Yutong Xiao
• Created: 21/Jul/21 02:39
• Updated: 31/Jul/21 18:29
• Resolved: 30/Jul/21 13:48

Description

In the method getBlock in CombinedBC, there is a TODO comment as follows:

@Override
  public Cacheable getBlock(BlockCacheKey cacheKey, boolean caching,
      boolean repeat, boolean updateCacheMetrics) {
    // TODO: is there a hole here, or just awkwardness since in the lruCache getBlock
    // we end up calling l2Cache.getBlock.
    // We are not in a position to exactly look at LRU cache or BC as BlockType may not be getting
    // passed always.
    boolean existInL1 = l1Cache.containsBlock(cacheKey);
    if (!existInL1 && updateCacheMetrics && !repeat) {
      // If the block does not exist in L1, the containsBlock should be counted as one miss.
      l1Cache.getStats().miss(caching, cacheKey.isPrimary(), cacheKey.getBlockType());
    }
    return existInL1 ?
        l1Cache.getBlock(cacheKey, caching, repeat, updateCacheMetrics):
        l2Cache.getBlock(cacheKey, caching, repeat, updateCacheMetrics);
  }

The TODO comment is expired. While in CombinedBC, L2 is not the victim handler of L1.

Issue Links

• links to: GitHub Pull Request #3509
• links to: GitHub Pull Request #3510