Push updates from Integreat CMS to App

[svenseeberg]

The Integreat App currently relies on polling for fetching new messages from the CMS. It would be nice to implement pushing messages. This probably requires some kind of message queue.

Websockets are probably the best implementation. However, with WSGI, each requests blocks one worker process. That means we need more workers to ensure that we do not end up in an exhaustion of processes. This would be the easiest implementation and could probably suffice for multiple chats at a time.

A better alternative would be switching to ASGI. This allows one worker to handle multiple requests. Apache HTTP does not support ASGI and we would therefore have to switch to Nginx.

More info:

• https://websockets.readthedocs.io/en/stable/howto/django.html
• https://channels.readthedocs.io/en/latest/
• https://www.geeksforgeeks.org/difference-between-asgi-and-wsgi-in-django/
• https://www.computerwoche.de/article/2815440/die-zukunft-der-python-webentwicklung.html