[HDFS-14761] RBF: MountTableResolver cannot invalidate cache correctly

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0
• Component/s: rbf
• Labels: RBF
• Hadoop Flags: Reviewed
• Tags: RBF
• Assignee: Yuxuan Wang
• Reporter: Yuxuan Wang
• Created: 21/Aug/19 03:23
• Updated: 23/Aug/19 17:51
• Resolved: 23/Aug/19 17:46

Description

STEPS TO REPRODUCE:
add mount table entry 1->/
mountTable.getDestinationForPath("/foo/a") will return "1->/foo/a", that's correct
add mount table entry 2->/foo
mountTable.getDestinationForPath("/foo/a") should return "2->/foo/a", but it still return "1->/foo/a"
WHY:

MountTableResolver.java

private void invalidateLocationCache(...)
{
    ...
    String src = loc.getSourcePath();
    if (src != null) {
        if (isParentEntry(src, path)) {
          LOG.debug("Removing {}", src);
          it.remove();
        }
    }
    ...
}

path is the new entry, in our case is "/foo"
But src is the mount point path, in our case is "/", which isn't child of "/foo"
So, it can't invalidate the cache entry.
HOW TO FIX:
Just reverse the parameters of isParentEntry .
PS:
PathLocation#getSourcePath() will return PathLocation#sourcePath, which attached a comment about "Source path in global namespace.". But I think the field indeed denotes the mount point path after I review the code. I think it's confused.

Issue Links

• links to: GitHub Pull Request #1334