A Brief History of Channels

A talk I gave at DjangoCon Europe 2016

Transcript

1. Andrew Godwin @andrewgodwin BRIEF HISTORY of CHANNELS A
2. Andrew Godwin Hi, I'm Django core developer Senior Software Engineer at Likes networking a little bit too much
3. Channels
4. Channels?
5. WebSocket
6. HTTP 1 request response Browser Server request response request response request response
7. HTTP 2 request response Browser Server request response request 1 response 2 request 2 response 1
8. WSGI request response Browser Server Django call app return val
9. WebSockets receive send Browser Server send receive send send
10. receive send Browser Server send receive send send Django ?
11. Hard to deadlock Built-in authorisation Scales down Widely deployable Optional
12. Django is not built for this.
13. But what if it was?
14. Instead of requests, we have events
15. Events of the same type are grouped on a named channel
16. HTTP requests HTTP responses WebSocket connecteds WebSocket frames received WebSocket frames sent WebSocket disconnections
17. A channel is a: named, first-in-first-out, at-most-once, non-broadcast, network-transparent queue of messages
18. http.request Protocol Server Worker Server http.response websocket.connect websocket.send websocket.receive websocket.send websocket.send
19. Responses are on single-reader channels (http.response!1A2B3C)
20. You can send onto channels from anywhere
21. How do you use it?
22. View request response callable
23. Consumer event event callable event event
24. Every message on a channel runs the consumer function
25. http.request routes to a view system consumer
26. def ws_message(message): # Get things from message data = json.loads(message['text']) # Use ORM like normal MyModel.objects.create( value=data['value'], ) # Send a reply and close socket message.reply_channel.send({ 'text': 'OK', 'close': True, })
27. routing.py: urls.py for Channels
28. message.user: like request.user
29. message.channel_session: per-socket sessions
30. Groups broadcast/pub-sub
31. Add a channel to a Group Remove a channel from a Group Send to a Group
32. Worked Examples github.com/andrewgodwin/channels-examples
33. Liveblog http.request Django view layer websocket.connect Add to liveblog Group websocket.disconnect Remove from liveblog Group <Article.save> Send notification to liveblog
34. Chat http.request Django view layer websocket.receive Either add to room Group or send to chat_messages websocket.disconnect Remove from room Groups chat_messages Send to room Groups
35. It's so easy to join! CALL NOW
36. Things I didn't even get to: Replacing WSGI Pluggable channel backends Sharding and scaling It's still just runserver
37. A base for the future Scheduler? Retry logic? Generic Consumers? ...and much more
38. 1.10 "Provisional"?
39. 1.8 1.9 pip install channels
40. channels.readthedocs.com github.com/andrewgodwin/channels-examples
41. Thanks. Andrew Godwin @andrewgodwin