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https://issues.apache.org/jira/browse/HBASE-2234?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12841995#action_12841995
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Nicolas Spiegelberg commented on HBASE-2234:
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Will correct comment/messaging issues. The actual patch should work fine
without append support, however I would lean towards applying HDFS-200 just to
exercise this test. In the unit test, we really just use append support for
syncFs(), since it's a deterministic way to initialize the pipeline for reading
[I'll clarify in code comments]. I've experimented with modifying
"io.file.buffer.size", but it would take a lot more introspection and another
nastiness to test it that way. My biggest worry about 'skipping the test' is
that it's easy to accidentally replace the default with an un-patched JAR and
not know about it since HBase has hundreds of tests. We've been regularly
applying new HDFS client-side patches over here for append support, and I
messed up once or twice when I was task switching between this issue and other
testing.
> Roll Hlog if any datanode in the write pipeline dies
> ----------------------------------------------------
>
> Key: HBASE-2234
> URL: https://issues.apache.org/jira/browse/HBASE-2234
> Project: Hadoop HBase
> Issue Type: Improvement
> Components: regionserver
> Reporter: dhruba borthakur
> Assignee: Nicolas Spiegelberg
> Priority: Blocker
> Fix For: 0.20.4, 0.21.0
>
> Attachments: HBASE-2234-20.4-1.patch, HBASE-2234-20.4.patch
>
>
> HDFS does not replicate the last block of a file that is being written to.
> This means that is datanodes in the write pipeline die, then the data blocks
> in the transaction log would be experiencing reduced redundancy. It would be
> good if the region server can detect datanode-death in the write pipeline
> while writing to the transaction log and if this happens, close the current
> log an open a new one. This depends on HDFS-826
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