[jira] [Resolved] (HBASE-26094) In branch-1 L2 BC should not be the victimhandler of L1 BC when using combined BC

["Reid Chan (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-26094?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Reid Chan resolved HBASE-26094.
-------------------------------
    Fix Version/s: 1.7.2
     Hadoop Flags: Reviewed
       Resolution: Fixed

> In branch-1 L2 BC should not be the victimhandler of L1 BC when using combined BC
> ---------------------------------------------------------------------------------
>
>                 Key: HBASE-26094
>                 URL: https://issues.apache.org/jira/browse/HBASE-26094
>             Project: HBase
>          Issue Type: Bug
>          Components: BlockCache
>    Affects Versions: 1.7.0
>            Reporter: Yutong Xiao
>            Assignee: Yutong Xiao
>            Priority: Major
>             Fix For: 1.7.2
>
>
> Currently in branch-1, the block cache initialisation is:
> {code:java}
>   LruBlockCache l1 = getL1(conf);
>     // blockCacheDisabled is set as a side-effect of getL1Internal(), so check it again after the call.
>     if (blockCacheDisabled) return null;
>     BlockCache l2 = getL2(conf);
>     if (l2 == null) {
>       GLOBAL_BLOCK_CACHE_INSTANCE = l1;
>     } else {
>       boolean useExternal = conf.getBoolean(EXTERNAL_BLOCKCACHE_KEY, EXTERNAL_BLOCKCACHE_DEFAULT);
>       boolean combinedWithLru = conf.getBoolean(BUCKET_CACHE_COMBINED_KEY,
>         DEFAULT_BUCKET_CACHE_COMBINED);
>       if (useExternal) {
>         GLOBAL_BLOCK_CACHE_INSTANCE = new InclusiveCombinedBlockCache(l1, l2);
>       } else {
>         if (combinedWithLru) {
>           GLOBAL_BLOCK_CACHE_INSTANCE = new CombinedBlockCache(l1, l2);
>         } else {
>           // L1 and L2 are not 'combined'.  They are connected via the LruBlockCache victimhandler
>           // mechanism.  It is a little ugly but works according to the following: when the
>           // background eviction thread runs, blocks evicted from L1 will go to L2 AND when we get
>           // a block from the L1 cache, if not in L1, we will search L2.
>           GLOBAL_BLOCK_CACHE_INSTANCE = l1;
>         }
>       }
>       l1.setVictimCache(l2);
>     }
> {code}
> As the code above, L2 will always be the victimhandler of L1, no matter if we use combined blockcache or not. But as logic (in master & branch-2) L2 should not be the victimhandler of L1 when using combined BC. We should set the victimhandler only when we use InclusiveConbinedBC or we do not use CombinedBC.



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