Instantiating a FileSystem object should guarantee the existence of the working
directory
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Key: HADOOP-2025
URL: https://issues.apache.org/jira/browse/HADOOP-2025
Project: Hadoop
Issue Type: Improvement
Components: fs
Affects Versions: 0.14.1
Reporter: Sameer Paranjpye
Fix For: 0.16.0
Issues like HADOOP-1891 and HADOOP-1916 illustrate the need for this behavior.
In HADOOP-1916 the problem is that the default working directory for a user on
HDFS '/user/<username>' does not exist. This results in the command 'hadoop dfs
-copyFromLocal foo ." creating a *file* called /user/<username> and copying the
contents of the file 'foo' into this file.
HADOOP-1891 is basically the same problem. The problem that Olga observed was
that copying a file to '.' on HDFS when her 'home directory' did not exist
resulted in the creation of a file with the path as her home directory. The
problem is incorrectly filed as a bug in the Path class. The behavior of Path
is correct, as Doug points out, it is perfectly reasonable for Path(".") to
convert to an empty path. When this empty path is resolved in HDFS or any other
filesystem the resolution to '/user/<username>' is also correct (at least for
HDFS). The problem IMO is that the existence of the working directory is not
guaranteed.
When I log in to a machine my default working directory is '/home/sameerp' and
filesystem operations that I execute with relative paths all work correctly
because this directory exists. My home directory lives on a filer, in the event
of it being unmountable the default working directory I get is '/' which also
is guaranteed to exist.
In the context of Hadoop, instantiating a FileSystem object is the analogue of
logging in and should result in a working directory whose existence has been
validated. In the case of HDFS this should be '/user/<username>' or '/' if the
directory does not exist.
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