A Brief History of Channels

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