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https://issues.apache.org/jira/browse/HADOOP-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12638625#action_12638625
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Doug Cutting commented on HADOOP-4044:
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Konstantin> checked exceptions can be used when a particular layer does not
have an immediate response to the condition causing the exception
First, in this case, I consider HDFS to be a single layer, or module. HDFS
controls all of its components. The calls on the stack above that are still
part of HDFS are known to HDFS, are under HDFS's control and are modified in a
coordinated manner, as a unit. In particular, all of HDFS knows that a link
can be to an external FileSystem, since this is a generic property of all
FileSystems. This is a safe assumption for any code in HDFS to make, and does
not violate any abstraction boundaries within HDFS.
An exception is justified when the best handler for it is unknown. It is not
the immediacy of the handler, or the proximity of the handler, but whether the
handler is fully determined. If the handler is known, then exceptions are just
being used as a convenient message passing channel. When the destination is
known, methods, parameters and return values are the preferred message passing
mechanisms in object-oriented programming.
Does that address your question?
> 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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