[HADOOP-3549] meaningful errno values in libhdfs

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.17.1
• Fix Version/s: 0.19.0

Environment

any POSIX

• Hadoop Flags: Reviewed
• Release Note: Improved error reporting for libhdfs so permission problems now return EACCES.
• Assignee: Ben Slusky
• Reporter: Ben Slusky
• Created: 12/Jun/08 18:42
• Updated: 08/Jul/09 17:05
• Resolved: 18/Aug/08 21:48

Description

A comment near the top of hdfs.h says that "All APIs set errno to meaningful values." Unfortunately this is a big fat lie – bigger and fatter still now that we have permissions in HDFS. If Hadoop throws an AccessControlException, then libhdfs sets errno to EINTERNAL, even though this is not an "internal" error in any sense of the word.

With the attached patches, allow libhdfs to derive a useful errno value when an exception is thrown. I've implemented handling for AccessControlException and a few others whose semantics seem obvious.

Tangential question: The signatures for invokeMethod() and constructNewObjectOfClass() in hdfsJniHelper.h disagreed with their comments. Was the "exc" argument of those functions removed in the past, or never implemented? I (re)instated it in my patch.

Issue Links

• is related to: HADOOP-3536 Support permissions in fuse-dfs
• relates to: HADOOP-3264 libhdfs does not provide permissions in API