Walkthrough the basic of Python Channels

Goal of writing this blog

• Figure out terminologies in Channels project
  • For example, Consumers, Channel layer

• As an ASGI application, how Channels bridge up with existing Django codes
• Expressed in code path for traffic in and out between Django and Daphne
• What are the interactions between Channels layer, and Consumers

Terminologies

Consumers[1][2]

• basic consumers - individual pieces that might handle chat messaging, or notifications - and tie them together with URL routing, protocol detection and other handy things to make a full application.

• A consumer is the basic unit of Channels code. We call it a consumer as it consumes events, but you can think of it as its own tiny little application.

• Consumers can be either long running / short running depends on the scope that consumer handling

• a rich abstraction that allows you to make ASGI applications easily.

(Channels) Router[1][2]

• A way to combine multiple consumers into 1 asgi application

• Channels router works on scope level instead of event level
  • Distribute per scope instead of per event

Channel Layer[1][2]

• channel layer, a low-level abstraction around a set of transports that allow you to send information between different processes.

• A solution to communicate between different application instances

• Each application should has an unique channel name

• Allows both point-to-point, and broadcast messaging

Worker

• A solution from project Channels, which running as a standalone process, on processing some naive background tasks. A worker will listen, and fire events from databases (Redis, Postgres etc) through Channel Layer

• IMO, we can view this as kind of a celery worker

Channels and Django

From Daphne to Django

• Invoke through … django asgi application definitnion …
• channels.routing.ProtocolTypeRouter
• channels.http.AsgiHandler
• …
• … Corresponding django view …

From Django to Daphne

• … Corresponding Django view …
• ….
• channels.http.AsgiHandler.get_response
• … Call send() which come from Daphne …

Ecosystem of Channels

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