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https://issues.apache.org/jira/browse/HDFS-5563?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13832212#comment-13832212
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Jing Zhao commented on HDFS-5563:
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The patch looks good overall. Some minor:
# Instead of using fromRead as parameter, how about using a parameter in the
opposite way like "toCache"? Also please add javadoc for this new parameter.
# It's better to use assertEquals(expected, actual) instead of
assertTrue(expected == actual value) in the unit test.
# A possible optimization here may be to directly return the local buffered
data for the read request without calling hsync. This may be addressed in
future jiras.
> NFS gateway should commit the buffered data when read request comes after
> write to the same file
> ------------------------------------------------------------------------------------------------
>
> Key: HDFS-5563
> URL: https://issues.apache.org/jira/browse/HDFS-5563
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: nfs
> Reporter: Brandon Li
> Assignee: Brandon Li
> Attachments: HDFS-5563.001.patch
>
>
> HDFS write is asynchronous and data may not be available to read immediately
> after write.
> One of the main reason is that DFSClient doesn't flush data to DN until its
> local buffer is full.
> To workaround this problem, when a read comes after write to the same file,
> NFS gateway should sync the data so the read request can get the latest
> content. The drawback is that, the frequent hsync() call can slow down data
> write.
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