Make dot a valid HDFS path?
---------------------------
Key: HBASE-2050
URL: https://issues.apache.org/jira/browse/HBASE-2050
Project: Hadoop HBase
Issue Type: Improvement
Reporter: Eli Collins
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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