Hi.
It seems like there may be a bug in VFS's ZipFileSystem. This seems to
still exist on trunk.
ZipFileSystem.init() recurses through the zip file and stuffs
ZipFileObjects in the cache. The cache is by default using soft
references to hold onto the files. The ZipFileSystem makes sure that
all of the ZipFileObjects hold strong references onto all of the other
ZipFileObjects. However, the FileSystem itself doesn't hold a strong
reference to any of the ZipFileObjects.
So if the soft reference to the file objects gets cleared, but the
filesystem is strongly held, it's possible that it appears as though
there are no files in the zip file, since ZipFileSystem only works for
files that are in the cache. (It's createFile() implementation only
returns files that appear not to exist.)
We see this happening intermittently in production environments, where
zip/jar files that clearly exist and clearly contain the file in
question occasionally throw exceptions stating that the file or
directory does not exist. This seems to happen more often very early in
the process when there are no other hard references to these files.
Once possible fix maybe to simply hold strongly onto the array of
ZipFileObjects in the ZipFileSystem; I have a two line patch that does
this. This has obvious memory consequences. However the filesystem
itself seems to be softly held in the cache and could be collected, and
furthermore I don't see that the system is correct otherwise.
Thanks,
-c
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