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https://issues.apache.org/jira/browse/HADOOP-4379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12667212#action_12667212
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dhruba borthakur commented on HADOOP-4379:
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@Jim: The SequenceFile.Writer.sync() does not actually invoke the
FSDataOutputStream.sync.
The FSDataOutputStream.sync() is a heavy weight operation and the
SequenceFile.Writer.sync() is typically invoked with small chunks of data,
that's the reason why the SequenceFile class does not automatically invoke the
fs sync call.
I changed your test case to invoke the FSDaOutputStream.sync call but still see
some problems. Will post an update as soon as I get to the bottom of this.
> In HDFS, sync() not yet guarantees data available to the new readers
> --------------------------------------------------------------------
>
> Key: HADOOP-4379
> URL: https://issues.apache.org/jira/browse/HADOOP-4379
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: dhruba borthakur
> Fix For: 0.19.1
>
> Attachments: 4379_20081010TC3.java, fsyncConcurrentReaders.txt,
> fsyncConcurrentReaders3.patch, Reader.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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