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https://issues.apache.org/jira/browse/HDFS-200?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12830334#action_12830334
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Todd Lipcon commented on HDFS-200:
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Regarding above comment - I suppose it doesn't entirely matter, since you only
care about getting the true file length if you're reading
at the end of the file. So, when you get near the end (10 blocks away) you'll
get the updated length. However, you'll still do useless
getBlockInfo calls on earlier blocks in the file. Perhaps some check against
the LocatedBlocks structure to see if the last block
in the block list is actually the same as the last block of the file is in
order?
> In HDFS, sync() not yet guarantees data available to the new readers
> --------------------------------------------------------------------
>
> Key: HDFS-200
> URL: https://issues.apache.org/jira/browse/HDFS-200
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: dhruba borthakur
> Priority: Blocker
> Attachments: 4379_20081010TC3.java, fsyncConcurrentReaders.txt,
> fsyncConcurrentReaders11_20.txt, fsyncConcurrentReaders12_20.txt,
> fsyncConcurrentReaders13_20.txt, fsyncConcurrentReaders14_20.txt,
> fsyncConcurrentReaders15_20.txt, fsyncConcurrentReaders3.patch,
> fsyncConcurrentReaders4.patch, fsyncConcurrentReaders5.txt,
> fsyncConcurrentReaders6.patch, fsyncConcurrentReaders9.patch,
> hadoop-stack-namenode-aa0-000-12.u.powerset.com.log.gz,
> hdfs-200-ryan-existing-file-fail.txt, hypertable-namenode.log.gz,
> namenode.log, namenode.log, Reader.java, Reader.java, reopen_test.sh,
> ReopenProblem.java, Writer.java, Writer.java
>
>
> In the append design doc
> (https://issues.apache.org/jira/secure/attachment/12370562/Appends.doc), it
> says
> * A reader is guaranteed to be able to read data that was 'flushed' before
> the reader opened the file
> However, this feature is not yet implemented. Note that the operation
> 'flushed' is now called "sync".
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