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https://issues.apache.org/jira/browse/HDFS-6984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14123412#comment-14123412
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Chris Nauroth commented on HDFS-6984:
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bq. So, it looks like DistCp depends on FileStatus being writable...
Last time I looked at this, I actually planned on replacing DistCp's usage of
{{FileStatus}} serialization with its own custom data type. I believe it
doesn't need all of the fields of {{FileStatus}}, so there is potential for a
marginal space/performance improvement by omitting the unnecessaries.
> In Hadoop 3, make FileStatus no longer a Writable
> -------------------------------------------------
>
> Key: HDFS-6984
> URL: https://issues.apache.org/jira/browse/HDFS-6984
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 3.0.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-6984.001.patch
>
>
> FileStatus was a Writable in Hadoop 2 and earlier. Originally, we used this
> to serialize it and send it over the wire. But in Hadoop 2 and later, we
> have the protobuf {{HdfsFileStatusProto}} which serves to serialize this
> information. The protobuf form is preferable, since it allows us to add new
> fields in a backwards-compatible way. Another issue is that already a lot of
> subclasses of FileStatus don't override the Writable methods of the
> superclass, breaking the interface contract that read(status.write) should be
> equal to the original status.
> In Hadoop 3, we should just make FileStatus no longer a writable so that we
> don't have to deal with these issues. It's probably too late to do this in
> Hadoop 2, since user code may be relying on the ability to use the Writable
> methods on FileStatus objects there.
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