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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4044) Create symbolic links in HDFS
Date Tue, 07 Oct 2008 01:03:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12637335#action_12637335
] 

Sanjay Radia commented on HADOOP-4044:
--------------------------------------

Owen says:
>My preference is toward not using exceptions for nominal cases, and I agree with Doug
that links seem like nominal cases. Clearly, however, it isn't a slam dunk.
>At the fear of crossing streams, I think that the classes like FSLinkBoolean are problematic.
I think we are better off creating a type for each method's return type. I think that a lot
of these return types should implement a class/interface (Owen ducks) that provides the common
interface for dereferencing the links.

What you loose with  owen's class/interface suggestion is that the signature not longer indicates

that the method returns a boolean or an array of locatedBlocks or an  file descriptor etc.
 I think Dhruba was trying to preserve that aspect of the original interfaces where by reading
the name of the method and the names and types of the
input and output parameter, once can easily guess the semantics of the method.
 (the eraser I threw at Owen bounced off the screen). 
But Owen is right in that his approach is a little more future proof (and exceptions are more
 future proof :-)

Owen what do you propose for the internal interfaces in the name node? -- do you suggest that
we remove the symlink-related-exception  and use your structure  every where in the FS and
HDFS code?
If not, why the inconsistency? 

> 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: 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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