SQLite: lazy load operation of attribute 'playlist' cannot proceed

When running Engine with SQLite exceptions like following are thrown:

Exception in thread PLAY:do_play:1642780440.0:
Traceback (most recent call last):
  File "/usr/lib/python3.9/threading.py", line 973, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.9/threading.py", line 1286, in run
    self.function(*self.args, **self.kwargs)
  File "/home/david/code/aura/engine/src/control.py", line 293, in wrapper_func
    if param: self.func(param,)
  File "/home/david/code/aura/engine/src/scheduling/scheduler.py", line 535, in do_play
    self.logger.info(self.engine.scheduler.timeslot_renderer.get_ascii_timeslots())
  File "/home/david/code/aura/engine/src/scheduling/utils.py", line 235, in get_ascii_timeslots
    rest_of_playlist = active_entry.get_next_entries(False)
  File "/home/david/code/aura/engine/src/scheduling/models.py", line 640, in get_next_entries
    for entry in self.playlist.entries:
  File "/usr/lib/python3/dist-packages/sqlalchemy/orm/attributes.py", line 294, in __get__
    return self.impl.get(instance_state(instance), dict_)
  File "/usr/lib/python3/dist-packages/sqlalchemy/orm/attributes.py", line 730, in get
    value = self.callable_(state, passive)
  File "/usr/lib/python3/dist-packages/sqlalchemy/orm/strategies.py", line 717, in _load_for_state
    raise orm_exc.DetachedInstanceError(
sqlalchemy.orm.exc.DetachedInstanceError: Parent instance <PlaylistEntry at 0x7fd8d5b65280> is not bound to a Session; lazy load operation of attribute 'playlist' cannot proceed (Background on this error at: http://sqlalche.me/e/13/bhk3)

changed milestone to %1.0-alpha2 — Precise Pheasant

added P3 label

marked this issue as related to #75 (closed)

marked this issue as related to #89 (closed)

added bug label

marked this issue as related to #90 (closed)

added To Do label

mentioned in issue #89 (closed)

Yes, indeed currently many functions return database objects. These objects cannot be accessed reliably, after the database session is closed. For example see Timeslot.for_datetime.

I see the following approaches for solving this issue:

• A) move the database session at least one level up, whenever a function returns a complete database object
• B) open and close the session in the request handler (Django uses this approach behind the scenes)

Regarding tests: this issue is currently not detected by the tests. Any ideas, how we could detect such situations?

See !11 (merged) for an approach described as (B).

mentioned in merge request !11 (merged)

Thanks a lot, that issue is gone.

Regarding tests: this issue is currently not detected by the tests. Any ideas, how we could detect such situations?

This would require an integration test, including an (simulated) Playout API endpoint.

I think option number D) as described in !11 (merged) could increase testability a lot.

mentioned in commit 0a675430

closed

assigned to @sumpfralle