Flask-socketio: Flask sqlalchemy

[EndenDragon]

Is there something I need to know before using flask-sqlalchemy in socketio handlers? (Like closing the session, if that is a thing)

[miguelgrinberg]

Yes. The teardown_context handler that Flask-SQLAlchemy installs to get the session cleaned up at the end of each request is obviously not called in a Socket.IO event handler which has no concept of a request, so you need to clean up the session after each database usage.

This is true not only for Socket.IO, but for any situation in which you use SQLAlchemy outside of a regular Flask HTTP request handler. I like to use a custom context manager to handle the session cleanup, as described in the SQLAlchemy docs: http://docs.sqlalchemy.org/en/latest/orm/session_basics.html#when-do-i-construct-a-session-when-do-i-commit-it-and-when-do-i-close-it

[EndenDragon]

If i close the sqlalchemy session with session.close(), does it "reopen" without making another HTTP request on the next socketio emit?

[miguelgrinberg]

Yes, the session is reopened the next time you use it. Also, you may want to use session.remove() instead of session.close(), like flask-sqlalchemy does.