[ZODB-Dev] Exception while closing ZODB

[Ulla Theiss]

Hello list,

since Version Zope 2.7.0 we have a problem closing the ZODB under Windows.

Sometime the class LockFile (in the file .../ZODB/lock_file.py) throws 
while unlinking the lockfile the Exception:
OSError: [Errno 13] Permission denied '....\\var\\...fs.lock'

We open and close ZODB-databases in different threads.
A look at the sourcecode in LockFile.close() shows, that
first
   unlock_file(self._fp)
   self._fp.close()

is called. Which means other threads and processes are able to use the 
locked file again.
Afterwards the lock-file should be deleted:

   os.unlink(self._path)

Therefore, if another thread already uses the lock-file, the first 
thread is unable to delete it and the
'Permission denied' exception is thrown.

As a workaround we put the os.unlink - statement in a try-except-block.

def close(self):
    if self._fp is not None:
        unlock_file(self._fp)
        self._fp.close()
        try:
            os.unlink(self._path)
            self._fp = None
        except:
            pass

How to correct the error best?

Best wishes,
Ulla Theiss.