SQLAlchemy+Tornado: How to create a scopefunc for SQLAlchemy's ScopedSession?

Question

Using tornado, I want to create a bit of middleware magic that ensures that my SQLAlchemy sessions get properly closed/cleaned up so that objects aren't shared from one request to the next. The trick is that, since some of my tornado handlers are asynchronous, I can't just share one session for each request.

So I am left trying to create a ScopedSession that knows how to create a new session for each request. All I need to do is define a scopefunc for my code that can turn the currently executing request into a unique key of some sort, however I can't seem to figure out how to get the current request at any one point in time (outside of the scope of the current RequestHandler, which my function doesn't have access to either).

Is there something I can do to make this work?

Answer 1

You might want to associate the Session with the request itself (i.e. don't use scopedsession if it's not convenient). Then you can just say, request.session. Still needs to have hooks at the start/end for setup/teardown.

edit: custom scoping function

def get_current_tornado_request():
   # TODO: ask on the Tornado mailing list how
   # to acquire the request currently being invoked

Session = scoped_session(sessionmaker(), scopefunc=get_current_tornado_request)