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https://issues.apache.org/jira/browse/HADOOP-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12639603#action_12639603
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Sanjay Radia commented on HADOOP-4044:
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_Doug Says: >Internal symlinks are supported automatically by local FS, at
least on unix. And support for remote symlinks on the local FS might be very
cool. Unix will gladly let me create symbolics link to anHDFS URI (Try 'ln -s
hdfs://foo/bar foo; ls -l foo'). These cannot be resolved by a unix shell, but
they could by 'bin/hadoop fs -ls', by MapReduce programs etc. One could, e.g.,
keep in one's home directory on unix links to the HDFS directories that one
commonly uses .._
It would be very cool to support them. (I guess unix thinks the : is simply
part of the name.)
BTW if someone happens to create a dir called "hdfs:" and valid path foo/bar
under it then the local file system will follow it and not return an error. Is
this a concern?
When trying to go through the remote mount symlink, the local file system
reports that the file does not exist. Hence, on a "file does not exist" error,
the client side lib will have to check if there are symlinks in the path. The
only snag is that "file not found error"s will take a little longer to report
as the
library ties to check if there is a symlink in the path. Is this an issue? Most
apps consider "file not found" to be an error and hence the speed of reporting
that is not a concern; however, there are some apps that create files if they
are missing and their performance will suffer a little.
> Create symbolic links in HDFS
> -----------------------------
>
> Key: HADOOP-4044
> URL: https://issues.apache.org/jira/browse/HADOOP-4044
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: HADOOP-4044-strawman.patch, symLink1.patch,
> symLink1.patch, symLink4.patch, symLink5.patch, symLink6.patch,
> symLink8.patch, symLink9.patch
>
>
> HDFS should support symbolic links. A symbolic link is a special type of file
> that contains a reference to another file or directory in the form of an
> absolute or relative path and that affects pathname resolution. Programs
> which read or write to files named by a symbolic link will behave as if
> operating directly on the target file. However, archiving utilities can
> handle symbolic links specially and manipulate them directly.
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