Combining websockets and WSGI in a python app

Question

I'm working on a scientific experiment where about two dozen test persons play a turn-based game with/against each other. Right now, it's a Python web app with a WSGI interface. I'd like to augment the usability with websockets: When all players have finished their turns, I'd like to notify all clients to update their status. Right now, everyone has to either wait for the turn timeout, or continually reload and wait for the "turn is still in progress" error message not to appear again (busy waiting, effectively).

I read through multiple websocket libraries' documentation and I understand how websockets work, but I'm not sure about the architecture for mixing WSGI and websockets: Can I have a websockets and a WSGI server in the same process (and if so, how, using really any websockets library) and just call my_websocket.send_message() from a WSGI handler, or should I have a separate websockets server and do some IPC? Or should I not mix them at all?

edit, 6 months later: I ended up starting a separate websockets server process (using Autobahn), instead of integrating it with the WSGI server. The reason was that it's much easier and cleaner to separate the two of them, and talking to the websockets server from the WSGI process (server to server communication) was straight forward and worked on the first attempt using websocket-client.

Answer 1

Here is an example that does what you want:

• https://github.com/tavendo/AutobahnPython/tree/master/examples/twisted/websocket/echo_wsgi

It runs a WSGI web app (Flask-based in this case, but can be anything WSGI conforming) plus a WebSocket server under 1 server and 1 port.

You can send WS messages from within Web handlers. Autobahn also provides PubSub on top of WebSocket, which greatly simplifies the sending of notifications (via WampServerProtocol.dispatch) like in your case.

• http://autobahn.ws/python

Disclosure: I am author of Autobahn and work for Tavendo.