I've been reading through the SQLAlchemy docs for a while now and am still
fairly confused about using SQLAlchemy with threaded processes. Hopefully
my specific question helps me understand things a little more...
I'm using the Pyramid framework with SQLAlchemy. The default scaffold for
this setup has the following line:
DBSession =
scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
I understand this essentially sets things up so in my web application I can
just do `DBSession.query(...)` and it automatically manages sessions for me
based on each web request. There's also some sort of interaction with this
and the `pyramid_tm` transaction manager. This is all fine for my regular
web application.
My problem comes up when I'm trying to create a portion of my application
which spawns several threads to listen for other tcp connections and then
save results in the database. Right now that portion of the application
maintains a 20-thread pool to handle incoming connections. I'm passing the
DBSession into the function that spawns the threads and then it's used as a
global variable similar to how the rest of the web application uses it. I
wanted to find out if this is the proper way of handling this.
I think since the sessions are thread-local there isn't any session sharing
across threads. However, I'm not sure how the "scoped_session()" works in
these long-running threads. I'm a little concerned that it's opening a
transaction and then sitting on it without ever committing... I'm really
not sure.
Should I change it so my threads instead use something like:
with transaction.manager:
DBSession.add(SomeORMObject(id=4))
or:
with DBSession.begin():
DBSession.add(SomeORMObject(id=4))
Will that commit the transaction and then release the session connection at
the end of the context?
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