DjangoCon Europe 2016 - A Brief History of Channels

Speaker: Andrew Godwin (twitter) is a core developer with Django and a senior developer at Eventbrite. Also, the author of channels.


Channels is Andrew's initiative to bring websockets to Django. Websockets are 6-7 years old and break the strict HTTP request-response pattern by allowing both parties to send or receive whenever they want. Websockets are open connections with unlimited bi-directional communication.


  • be hard to deadlock (deadlocks are a common problem with async communication)
  • built-in auth and security
  • easily deployable
  • scaling easily up and down
  • optional


Since Django is very much request-based, we'll swap out requests for events when using channels.

A channel is a named (identified via string), first-in-first-out (ordered), at-most-once (failure state is to drop the message), non-broadcast (only one listener will receive the message), network-transparent (will work over a network) queue of messages.

It's bascally breaking Django into two parts: a protocol server handling requests/events, and a worker server handling business logic.


It's included in Django 1.10 and installable (pip install channels) for Django 1.8 and 1.9 and will be maintained for all of these for a while. There is also extensive documentation. Even better, there are heavily annotated working examples - go read them!

You basically write a Consumer instead of a View. A Consumer is very similar (still callable, might be class or function). A consumer receives messages instead of requests, and doesn't return a value, but instead uses message.reply_channel.send({}), and that's it.

You can also use per-socket session with message.channel_session, and utilize Groups for broadcasting or pub/sub style communication. You can add and remove channels from a group and send messages to groups.


Channels has even more features not mentioned due to time constraints (replacing wsgi, pluggable backend, sharding and scaling, and it still works with just runserver). Down the road there might be a scheduler, retry logic, a generic consumer and many other great things.