Apache9 commented on code in PR #5506:
URL: https://github.com/apache/hbase/pull/5506#discussion_r1385891214
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hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/CombinedBlockCache.java:
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@@ -77,16 +81,49 @@ public void cacheBlock(BlockCacheKey cacheKey, Cacheable
buf) {
@Override
public Cacheable getBlock(BlockCacheKey cacheKey, boolean caching, boolean
repeat,
boolean updateCacheMetrics) {
- // We are not in a position to exactly look at LRU cache or BC as
BlockType may not be getting
- // passed always.
+ Cacheable block = null;
+ // We don't know the block type. We should try to get it on one of the
caches only,
+ // but not both otherwise we'll over compute on misses. Here we check if
the key is on L1,
+ // if so, call getBlock on L1 and that will compute the hit. Otherwise,
we'll try to get it from
+ // L2 and whatever happens, we'll update the stats there.
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());
+ // if we know it's in L1, just delegate call to l1 and return it
+ if (existInL1) {
+ block = l1Cache.getBlock(cacheKey, caching, repeat, false);
+ } else {
+ block = l2Cache.getBlock(cacheKey, caching, repeat, false);
+ }
+ if (updateCacheMetrics) {
+ boolean metaBlock = isMetaBlock(cacheKey.getBlockType());
+ if (metaBlock) {
+ if (!existInL1 && block != null) {
+ LOG.warn("Cache key {} had block type {}, but was found in L2
cache.", cacheKey,
Review Comment:
I think this is just a defensive logging? It should not happen normally. If
we see this log, then there could be a bug?
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