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https://issues.apache.org/jira/browse/HBASE-28338?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Bryan Beaudreault resolved HBASE-28338.
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Fix Version/s: 2.6.0
3.0.0-beta-2
Resolution: Fixed
> Bounded leak of FSDataInputStream buffers from checksum switching
> -----------------------------------------------------------------
>
> Key: HBASE-28338
> URL: https://issues.apache.org/jira/browse/HBASE-28338
> Project: HBase
> Issue Type: Bug
> Reporter: Bryan Beaudreault
> Priority: Major
> Labels: pull-request-available
> Fix For: 2.6.0, 3.0.0-beta-2
>
>
> In FSDataInputStreamWrapper, the unbuffer() method caches an unbuffer
> instance the first time it is called. When an FSDataInputStreamWrapper is
> initialized, it has hbase checksum disabled.
> In HFileInfo.initTrailerAndContext we get the stream, read the trailer, then
> call unbuffer. At this point, checksums have not been enabled yet via
> prepareForBlockReader. So the call to unbuffer() caches the current
> non-checksum stream as the unbuffer instance.
> Later, in initMetaAndIndex we do a similar thing. This time,
> prepareForBlockReader has been called, so we are now using hbase checksums.
> When initMetaAndIndex calls unbuffer(), it uses the old unbuffer instance
> which actually has been closed when we switched to hbase checksums. So that
> call does nothing, and the new no-checksum input stream is never unbuffered.
> I haven't seen this cause an issue with normal hdfs replication (though
> haven't gone looking). It's very problematic for Erasure Coding because
> DFSStripedInputStream holds a large buffer (numDataBlocks * cellSize, so 6mb
> for RS-6-3-1024k) that is only used for stream reads NOT pread. The
> FSDataInputStreamWrapper we are talking about here is only used for pread in
> hbase, so those 6mb buffers just hang around totally unused but
> unreclaimable. Since there is an input stream per StoreFile, this can add up
> very quickly on big servers.
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