[HBASE-26083] L1 miss metric is incorrect when using CombinedBlockCache

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.3.6, 3.0.0-alpha-2, 2.4.5, 1.7.2
• Component/s: BlockCache
• Hadoop Flags: Reviewed
• Assignee: Yutong Xiao
• Reporter: Yutong Xiao
• Created: 12/Jul/21 08:56
• Updated: 17/Jul/21 02:25
• Resolved: 16/Jul/21 05:38

Description

In CombinedBlockCache getBlock method

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.
    return l1Cache.containsBlock(cacheKey)?
        l1Cache.getBlock(cacheKey, caching, repeat, updateCacheMetrics):
        l2Cache.getBlock(cacheKey, caching, repeat, updateCacheMetrics);
  }

If L1 does not contains cacheKey, it will never check it in L1, so that L1 miss metrics is always 0.

Issue Links

• links to: GitHub Pull Request #3473
• links to: GitHub Pull Request #3474
• links to: GitHub Pull Request #3491