HTTP Socketio session not in sync

[Joe-ChenZ]

Most of the time, the sessions are in sync. I am using Server-side managed session with manage_session = False. Socketio session updates with HTTP and vice versa. However, when I use chrome inspect and delete the session cookies. HTTP gets that the session is deleted. Socketio session stays the same. I know Socketio Session is a fork from HTTP, but wouldn't manage_session=False solve it?

[Joe-ChenZ]

If i go to the flask side and set the expiry time to like 10s, and i wait for it to expire, then it wouldn't have this issue

[miguelgrinberg]

Going to the browser manually to delete a cookie is not a "normal" use case. When you delete a cookie nothing happens on the WebSocket connection, there is no signal or anything else that informs the WebSocket that the session cookie is gone. If you refresh the page after you delete the cookie then the reconnected WebSocket will be in sync.

[miguelgrinberg]

Take the sessions.py example in this repository and modify it so that it shows the problem. Send me the changed app and I'll debug it here.

[Joe-ChenZ]

i found my frontend bug. it was a race condition issue. Thanks. I do have another question. You said that socketio updates the session after the handler ends? "end" means the handler has returned? I have a callback function in my sio handler. Does that behave the same as the socketio event handler <on_event_name>?

[miguelgrinberg]

It will also save the session when the callback function returns.

[Joe-ChenZ]

do you know if there is any overhead time cost from returning the function to saving the session? Now i am putting an arbitrary sleep time in my frontend (100ms) to wait for the session update before i retrieve user session info. Doesn't feel like the best practice

[miguelgrinberg]

If this is for a callback, then you really don't have much control, since the callback runs asynchronously.

To me it feels like this is a design problem. The user session is intended to be used as light storage for data that you want the server to remember between handlers. You seem to be using it as a database.