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https://issues.apache.org/jira/browse/HDFS-6984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15847736#comment-15847736
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Chris Douglas commented on HDFS-6984:
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bq. serialization that omits fields for efficiency isn't supportable, and is
why I'd prefer a PathHandle.
With this constraint, we either expand the API surface- adding functions that
accept PathHandle instances, rather than FileStatus- or all fields are required
in FileStatus objects. I see your point w.r.t. confused semantics for partial
FileStatus objects. In completeness, we could change the return type to
{{Optional<T>}} for FileStatus fields, but that's a nonstarter from a
compatibility perspective.
We can pick this up in HDFS-7878.
bq. I don't feel that strongly about removing Writable, but the nowritable
patch is simple and to the point
Well... sure. Deleting code is direct. :) I don't mind moving the protobuf
serialization to a utility library. Would that move this forward?
bq. Cross-serialization doesn't have an immediate usecase. HDFS-7878 IMO needs
a serializable PathHandle, not a full FileStatus.
The goal was not to make cross-serialization a requirement, but to make future
efficiency possible.
> In Hadoop 3, make FileStatus serialize itself via protobuf
> ----------------------------------------------------------
>
> Key: HDFS-6984
> URL: https://issues.apache.org/jira/browse/HDFS-6984
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 3.0.0-alpha1
> Reporter: Colin P. McCabe
> Assignee: Colin P. McCabe
> Labels: BB2015-05-TBR
> Attachments: HDFS-6984.001.patch, HDFS-6984.002.patch,
> HDFS-6984.003.patch, HDFS-6984.nowritable.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 serialize itself via protobuf 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 existing FileStatus
> serialization there.
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