Anoop Sam John created HBASE-16738:
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Summary: L1 cache caching shared memory HFile block when blocks
promoted from L2 to L1
Key: HBASE-16738
URL: https://issues.apache.org/jira/browse/HBASE-16738
Project: HBase
Issue Type: Sub-task
Affects Versions: 2.0.0
Reporter: Anoop Sam John
Assignee: Anoop Sam John
Fix For: 2.0.0
This is an issue when L1 and L2 cache used with combinedMode = false.
See in getBlock
{code}
if (victimHandler != null && !repeat) {
Cacheable result = victimHandler.getBlock(cacheKey, caching, repeat,
updateCacheMetrics);
// Promote this to L1.
if (result != null && caching) {
cacheBlock(cacheKey, result, /* inMemory = */ false, /* cacheData =
*/ true);
}
return result;
}
{code}
When block is not there in L1 and have it in L2, we will return the block read
from L2 and promote that block to L1 by adding it in LRUCache. But if the
Block buffer is having shared memory (Off heap bucket cache for eg:) , we can
not directly cache this block. The buffer memory area under this block can get
cleaned up at any time. So we may get block data corruption.
In such a case, we need to do a deep copy of the block (Including its buffer)
and then add that to L1 cache.
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