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https://issues.apache.org/jira/browse/HDFS-2006?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yi Liu updated HDFS-2006:
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Attachment: xattrs.patch
Dhruba, this JIRA has been sleeping for quite a while, do you mind if I
reassign it to me to take a stab at it? Attached is a preliminary patch I've
been working for extended attributes.
XAttrs(Extended attributes) are widely implemented on traditional Operating
Systems, such as Linux, Windows, Mac OS and so on. There are more and more
requirements for HDFS providing feature to store extended attributes for files
and directories, Hadoop transparent encryption and many upper layer components
desire this feature. Main points of the design are as following:
1. XAttrs feature will be implemented based on INode IFeature (HDFS-5284).
File/directory can have xattr.
2. XAttr is stored in NN memory, including both the name and value. The
preliminary patch and design doc focus on this, it will be fine for short
value, even so, it can satisfy many requirements.
3. For xattr with large value, it's not target of this phase. We can consider
it in next phase, large value is not suitable in NN precious memory, maybe we
can store it to something persisted elsewhere and have a reference in NN memory.
4. If XAttrs feature is not enabled, no additional memory and disk space is
required.
5. XAttr is POSIX Extended Attribute model, similar to the one in traditional
Operating Systems: http://en.wikipedia.org/wiki/Extended_file_attributes,
http://www.bestbits.at/acl/man/man5/attr.txt. Extended Attribute consists of a
name and associated data, and 4 namespaces are defined: user, trusted, security
and system. "setfattr" and "getfattr" will be supported as FsShell commands
which are same as in Linux.
For more information, please refer to the design doc which will be attached
later.
> ability to support storing extended attributes per file
> -------------------------------------------------------
>
> Key: HDFS-2006
> URL: https://issues.apache.org/jira/browse/HDFS-2006
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: xattrs.patch
>
>
> It would be nice if HDFS provides a feature to store extended attributes for
> files, similar to the one described here:
> http://en.wikipedia.org/wiki/Extended_file_attributes.
> The challenge is that it has to be done in such a way that a site not using
> this feature does not waste precious memory resources in the namenode.
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