Websockets integration with django @ KharkivPy

1. Websockets + Django
Ihor Harahatyi

2. Let's talk about:
Why we need websockets?
Why no WS in Django
Ways to get WS in Django
Not in this talk:
Async.io
How to develop a chat

3. Why to use websockets
Speed up transport
Bidirectional communication (live update)

4. Speed Up
Django web site
50K online
2M on peak
Q: How long it takes to render page?

5. A: 10 seconds
Use caching. Transfer is not your bottle neck with
Django

6. WSGI (pep333)
Request -> Middleware -> Process ->
Middleware -> Response

7. 1 connection = 1 process

8. So how to get live update?

9. Ask if there is anything new

10. Separate WS provider

11. node.js
- No python
- No django

12. tornado/gevent/async.io
- Yes python
- ? django

13. Recycling

14. Django awarded MOSS Grant $150,000 to help fund the
development of Channels, the initiative to rewrite the
core of Django to support (among other things)
WebSockets and background tasks, and to integrate key
parts of the Django REST Framework request/ response
code into Django, such as content negotiation.

15. Django channels
in Django 1.10 Going to be in Django
Django auth

16. Channel
FIFO
Message expiry
At-most-once delivery to one listener
#routing.py
from app.consumers import ws_add, ws_message,
ws_disconnect
channel_routing = {
"websocket.connect": ws_add,
"websocket.receive": ws_message,
"websocket.disconnect": ws_disconnect,
}

17. Group
#consumers.py
@receiver(post_save, sender=LiveMatch)
def send_update(sender, instance, **kwargs):
Group("scoreboard").send({
"match": json.dumps({
"id": instance.id,
"content": MatchSerializer(instance).data
})
})
def ws_connect(message):
Group("scoreboard").add(message.reply_channel)
def ws_disconnect(message):
Group("sco").discard(message.reply_channel)

18. Cons
Uses ASGI (Daphne)
In Beta
Django >= 1.8

19. django-websocket-redis
uWSGI offers websockets
Uses gevent for WS
One line in requirements.txt
Django >=1.5

20. Con g
Run two uwsgi instances
Connect to redis
#nginx
location / {
include /etc/nginx/uwsgi_params;
uwsgi_pass unix:/path/to/django.socket;
}
location /ws/ {
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_pass http://unix:/path/to/web.socket;
}

21. Django auth
def get_allowed_channels(request, channels):
if not request.user.is_authenticated():
raise PermissionDenied
Incoming messages:
#settings.py
WS4REDIS_SUBSCRIBER = MyRedisSubscriber

22. #views.py
from django.views.generic.base import View
from ws4redis.publisher import RedisPublisher
class MyTypicalView(View):
facility = 'unique-named-facility'
audience = {'broadcast': True}
def __init__(self, *args, **kwargs):
super(MyTypicalView, self).init(*args, **kwargs)
self.redis_publisher =
RedisPublisher(facility, **self.audience)
def get(self, request)
message = 'A message'
self.redis_publisher.publish_message(message)