I'm using SQLAlchemy 1.0.8 with an SQLite file-based database, running as
part of a Flask-based server, and getting some strange results.
I'm seeing this exception raised:
ProgrammingError: SQLite objects created in a thread can only be used
in that same thread.The object was created in thread id 8088 and this is
thread id 8672
The place where the exception is raised is in _finalize_fairy in pool.py,
and that's being called from the lambda in pool.py line 491. That in turn
is getting invoked from a completely unrelated piece of code, implying that
this is perhaps just coming off the back of a Python garbage collection
cycle or similar. The pool type at the time the exception is raised is a
NullPool object, but obviously _finalize_fairy is getting called at an
unexpected time when some of the operations are not valid.
This only happens when I don't explicitly close a session, which I accept
is a bug in my own code. I've fixed that so I don't trigger this behaviour
again. But is it correct (and safe) for _finalize_fairy to be called from
arbitrary threads like this? If there are thread-sensitive situations, such
as when using SQLite, perhaps attaching the clean-up logic to the callback
on a weakref is the wrong thing to do? Not that I'm sure what the
alternative would be...
Thanks,
Ben
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