[Exist-development] Problem with temp files on Windows

[Adam R. <ad...@ex...>]

It was bought to my attention that temporary files were not being
cleaned up on the Windows platform.

Basically if you use a memory mapped file in eXist-db, e.g. through
calling an operation on a stream, almost anything that returns
base64binary - e.g. request:get-data(), then temporary files are
created in $EXIST_HOME/tools/jetty/tmp
Simply opening eXide, and opening an XQuery from the database and
hitting refresh multiple times will cause the issue.

On Unix/Linux/Mac these files are deleted automatically by the
function finalize() calling tempFile.delete() in the class
org.exist.util.io.MemoryMappedFileFilterInputStreamCache.
This is the correct behaviour!

However... On Windows platforms, calling tempFile.delete() does not
delete the file and returns false, even attempting tricks with
System.gc() and a thread pause, which has been known to work around
the Windows JDK platform bugs in File.renameTo() does not work here.

I am at a loss as how to fix this on Windows platforms. I have also
checked JDK 7 on Windows, and the same problems exist there. If anyone
knows of a mechanism please let me know. I cannot find a solution via
Google so far.

At the moment, I can only imagine a workaround to re-use files that
cannot be deleted. This may be sufficient but far from perfect, and I
must say I loathe the fact that the Windows JDK really sucks here.

The code I used for debugging this behaviour, simply replace that
finalize method with -

@Override
    protected void finalize()
	throws Throwable
    {
        super.finalize();
	if(tempFile != null) {
            boolean deletedFile = tempFile.delete();
            System.err.println("deleted file (1st): " + deletedFile);
            if(!deletedFile) {
                System.gc();
                Thread.sleep(50);
                deletedFile = tempFile.delete();
                System.err.println("deleted file (2nd): " + deletedFile);
            }
        }
    }

-- 
Adam Retter

eXist Developer
{ United Kingdom }
ad...@ex...
irc://irc.freenode.net/existdb