Comment 2 for bug 1843099

Hello,

I looked deeper into this, I feel the issue may be with apt_pkg.get_lock's return value now. It seems the code considers 0 success whereas now an FD is returned which seems to mean it's fine.

# Example logging output
2019-09-06 10:54:31,249 WARNING - SIGTERM or SIGHUP received, stopping unattended-upgradesonly if it is running
2019-09-06 10:54:31,250 DEBUG - Starting countdown of 25.0 minutes
2019-09-06 10:54:31,250 DEBUG - get_lock returned 7
2019-09-06 10:54:31,250 DEBUG - lock not taken

# Tracing manually
/usr/share/unattended-upgrades/unattended-upgrade-shutdown:
L230> 2019-09-06 10:54:31,249 WARNING - SIGTERM or SIGHUP received, stopping unattended-upgradesonly if it is running
  * Bug - add space to end (i.e. "SIGTERM or SIGHUP received, stopping unattended-upgrades ")
L318> 2019-09-06 10:54:31,250 DEBUG - Starting countdown of 25.0 minutes
L333> 2019-09-06 10:54:31,250 DEBUG - get_lock returned 7
  * Bug - The lock should be acquired so it should be 0 ... according to code but docs say it's fine
  L332> res = apt_pkg.get_lock(self.options.lock_file)
  L333> logging.debug("get_lock returned %i" % res) # <-- This is where I believe there's the bug
  L334> # exit here if there is no lock
  L335> if res > 0:
  L336> logging.debug("lock not taken")
  L337> if self.lock_was_taken:
  L338> exit_log_result(self.signal_sent)
  L339> else:
  L340> sys.exit(0)
  L341> self.lock_was_taken = True
  L342> signal_stop_unattended_upgrade()
  L343> self.signal_sent = True
  L344> # show log
  L345> log_progress()
  L346> return True

  * Looking deeper into get_lock it shows that a file descriptor is returned
    vs -1 or an error raised. I believe the code may need to be updated as
    running python3 interactively, importing apt_pkg and printing its
    __doc__ shows the following. This is Sparta err python 3... so perhaps
    that's the reason.

>>> print(apt_pkg.get_lock.__doc__)
get_lock(file: str, errors: bool) -> int

Create an empty file of the given name and lock it. If the locking
succeeds, return the file descriptor of the lock file. Afterwards,
locking the file from another process will fail and thus cause
get_lock() to return -1 or raise an Error (if 'errors' is True).

From Python 2.6 on, it is recommended to use the context manager
provided by apt_pkg.FileLock instead using the with-statement.