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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6984) In Hadoop 3, make FileStatus serialize itself via protobuf
Date Thu, 16 Mar 2017 20:47:41 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15928873#comment-15928873
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Chris Douglas commented on HDFS-6984:
-------------------------------------

Thanks for taking a look, [~andrew.wang].

Sorry, I had forgotten your earlier comment. Should we also try to remove {{Writable}} from
{{FsPermission}}? We could deprecate the {{Writable}} API instead of removing it from these
classes, in case projects/users depend on it downstream... the serialization/conversion can
still live in a library, but be called from the deprecated methods.

Since both {{FsPermission#getAclBit}} and {{FsPermission#getEncryptedBit}}/{{FileStatus#isEncrypted}}
are user-facing, should these also be part of FSProtos? The payload for {{FileEncryptionInfoProto}}
is likely HDFS-specific, or I'd suggest populating these using the presence of the fields.
While we're at it, should we also change {{HdfsFileStatusProto}} to stop packing the acl/encryption
bits among the permission bits?

Kind of a sidebar: is there a reason encryption info is included in HdfsFileStatus, but ACLs
are not? Would it be inappropriate to add a {{FileSystem#getAclStatus(FileStatus)}}, in case
an implementation returns this information in its response (potentially avoiding the 2-RPC
overhead)?

I'll add some additional tests.

> 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-6984.004.patch,
HDFS-6984.005.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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