[HADOOP-7487] DF should throw a more reasonable exception when mount cannot be determined

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.23.0, 2.0.3-alpha, 3.0.0-alpha1
• Fix Version/s: 2.1.0-beta
• Component/s: fs
• Labels: noob
• Target Version/s: 2.1.0-beta
• Hadoop Flags: Reviewed
• Assignee: Andrew Wang
• Reporter: Todd Lipcon
• Created: 28/Jul/11 01:36
• Updated: 12/May/16 18:22
• Resolved: 26/Feb/13 01:44

Description

Currently, when using the DF class to determine the mount corresponding to a given directory, it will throw the generic exception "Expecting a line not the end of stream" if it can't determine the mount (for example if the directory doesn't exist).

This error message should be improved in several ways:

1. If the dir to check doesn't exist, we can see that before even execing df, and throw a better exception (or behave better by chopping path components until it exists)
2. Rather than parsing the lines out of df's stdout, collect the whole output, and then parse. So, if df returns a non-zero exit code, we can avoid trying to parse the empty result
3. If there's a success exit code, and we still can't parse it (eg incompatible OS), we should include the unparseable line in the exception message.