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https://issues.apache.org/jira/browse/HBASE-15366?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15175076#comment-15175076
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ramkrishna.s.vasudevan commented on HBASE-15366:
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bq.Why are there 50 bytes tagged on to the end of the hfileblock?
I know about that fetching that next block's header for some optimization
purpose but was not very sure on that 50 bytes thing. Ya worth fixing if it
does not make sense.
> Add doc, trace-level logging, and test around hfileblock
> --------------------------------------------------------
>
> Key: HBASE-15366
> URL: https://issues.apache.org/jira/browse/HBASE-15366
> Project: HBase
> Issue Type: Sub-task
> Components: BlockCache
> Affects Versions: 2.0.0
> Reporter: stack
> Assignee: stack
> Fix For: 2.0.0
>
> Attachments: 15366.patch, 15366v2.patch, 15366v3.patch,
> 15366v4.patch, 15366v4.patch
>
>
> What hfileblock is doing -- that it overreads when pulling in from hdfs to
> fetch the header of the next block to save on seeks; that it caches the block
> and overread and then adds an extra 13 bytes to the cached entry; that
> buckets in bucketcache have at least four hfileblocks in them and so on --
> was totally baffling me. This patch docs the class, adds some trace-level
> logging so you can see if you are doing the right thing, and then adds a test
> of file-backed bucketcache that checks that persistence is working.
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