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Date: Mon, 6 Oct 2008 09:39:44 -0700 (PDT)
From: "Doug Cutting (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-4044) Create symbolic links in HDFS
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    [ https://issues.apache.org/jira/browse/HADOOP-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12637133#action_12637133 ] 

Doug Cutting commented on HADOOP-4044:
--------------------------------------

Exceptions are intended for cases where you're not sure who will catch them.  They're a non-local control-flow mechanism.  Using them for normal control flow is an abuse and leads to spaghetti logic.  In this case we are changing the FileSystem service-provider interface so that many methods can return either a link or a normal value.  The appropriate implementation is a union result type, not exceptions.  In Java we implement this union by extending a 'Linkable' base class.

http://192.220.96.201/essays/java-style/exceptions.html
http://www.javapractices.com/topic/TopicAction.do?Id=19
http://leepoint.net/notes-java/flow/exceptions/03exceptions.html


> 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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