On 9/11/15 1:55 PM, Ben Sizer wrote:
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?
first off, this is an artificial limitation in the pysqlite driver that
can be disabled at the driver level if need be. No other driver
disallows even calling .close() from another thread. The error here is
within a weakref callback so I'm assuming it's only emitted as a warning.
secondly, what alternative behavior would you propose? Maybe at this
point we should *always* be emitting a warning when a weakref handler
ends up closing the connection.
Not that I'm sure what the alternative would be...
oh. Well there's your answer! our choices are 1. do nothing 2. use
garbage collection. 1. do nothing might be an actual option
considering that DBAPIs should be closing out their resources when their
connections are garbage collected, but I can imagine that not every
DBAPI does this very well.
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sqlalchemy.
For more options, visit https://groups.google.com/d/optout.
