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From "Eli Collins (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (HDFS-836) Make dot a valid HDFS path?
Date Sun, 14 Nov 2010 07:36:16 GMT

     [ https://issues.apache.org/jira/browse/HDFS-836?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Eli Collins resolved HDFS-836.
------------------------------

    Resolution: Later

I think we can punt this until it's requested.

> Make dot a valid HDFS path?
> ---------------------------
>
>                 Key: HDFS-836
>                 URL: https://issues.apache.org/jira/browse/HDFS-836
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Eli Collins
>         Attachments: hdfs-836-1.patch
>
>
> What do people think of making "." a valid path in HDFS? The motivation is to allow users
to create symlinks to the current directory in HDFS-245, eg see the following test for the
current behavior:
> {code}
>   @Test
>   /** Test create symlink to . */
>   public void testCreateLinkToDot() throws IOException {
>     Path dir  = new Path("/test");
>     Path link = new Path("/test/linkToDot");
>     fc.mkdir(dir, FileContext.DEFAULT_PERM, true);        
>     fc.setWorkingDirectory(dir);
>     try {
>       fc.createSymlink(new Path("."), link);
>       fail("Created symlink to dot");
>       readFile(new Path("/test/linkToDot/file"));
>     } catch (IOException x) {
>       // Expected. Path(".") resolves to "" because URI normalizes
>       // the dot away and AbstractFileSystem considers "" invalid.  
>     }
>     fc.delete(dir, true);
>   }
> {code}
> This involves trade offs since Hadoop Paths represent URIs (rather than the path component
of a URI) and in URIs dot normalizes away. Some options:
> # Make symlinks to "." an exception per the above, though it seems odd to consider ".",
"..", "/" etc invalid paths (and the latter two happen to work based on how the Path constructor
initializes the URI even though isValidName in AbstractFileSystem would consider them invalid
names.
> # Making "." immediately parse to an absolute path would be poor symlink semantics (eg
a link to "." should not break if you rename the link's parent directory). 
> # Making Path special case this so "." doesn't normalize away would be a weird one off
case where Path and URIs differ.
> Other alternatives? Of the above I'd prefer the last one.

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