Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Django and this thing called Channels
Search
Andrew Godwin
March 09, 2016
Programming
1
650
Django and this thing called Channels
A talk I gave at Python SF Meetup, March 2016.
Andrew Godwin
March 09, 2016
Tweet
Share
More Decks by Andrew Godwin
See All by Andrew Godwin
Reconciling Everything
andrewgodwin
1
260
Django Through The Years
andrewgodwin
0
160
Writing Maintainable Software At Scale
andrewgodwin
0
390
A Newcomer's Guide To Airflow's Architecture
andrewgodwin
0
310
Async, Python, and the Future
andrewgodwin
2
610
How To Break Django: With Async
andrewgodwin
1
660
Taking Django's ORM Async
andrewgodwin
0
670
The Long Road To Asynchrony
andrewgodwin
0
590
The Scientist & The Engineer
andrewgodwin
1
690
Other Decks in Programming
See All in Programming
nekko cloudにおけるProxmox VE利用事例
irumaru
3
420
採用事例の少ないSvelteを選んだ理由と それを正解にするためにやっていること
oekazuma
2
1k
コンテナをたくさん詰め込んだシステムとランタイムの変化
makihiro
1
120
Monixと常駐プログラムの勘どころ / Scalaわいわい勉強会 #4
stoneream
0
270
快速入門可觀測性
blueswen
0
330
数十万行のプロジェクトを Scala 2から3に完全移行した
xuwei_k
0
260
Refactor your code - refactor yourself
xosofox
1
260
CSC305 Lecture 25
javiergs
PRO
0
130
テストケースの名前はどうつけるべきか?
orgachem
PRO
0
130
Keeping it Ruby: Why Your Product Needs a Ruby SDK - RubyWorld 2024
envek
0
180
layerx_20241129.pdf
kyoheig3
2
290
Cloudflare MCP ServerでClaude Desktop からWeb APIを構築
kutakutat
1
530
Featured
See All Featured
Building Adaptive Systems
keathley
38
2.3k
Why Our Code Smells
bkeepers
PRO
335
57k
The Pragmatic Product Professional
lauravandoore
32
6.3k
Docker and Python
trallard
41
3.1k
Fontdeck: Realign not Redesign
paulrobertlloyd
82
5.3k
The Web Performance Landscape in 2024 [PerfNow 2024]
tammyeverts
2
290
Distributed Sagas: A Protocol for Coordinating Microservices
caitiem20
330
21k
The Success of Rails: Ensuring Growth for the Next 100 Years
eileencodes
44
6.9k
Writing Fast Ruby
sferik
628
61k
Scaling GitHub
holman
458
140k
Being A Developer After 40
akosma
87
590k
Visualizing Your Data: Incorporating Mongo into Loggly Infrastructure
mongodb
44
9.3k
Transcript
Andrew Godwin @andrewgodwin DJANGO and this thing called CHANNELS
Andrew Godwin Hi, I'm Django core developer Senior Software Engineer
at Likes complaining about networking
The Problem First: The Solution Then: The Future Finally:
The Problem WSGI ain't so bad
Browser HTTP Webserver Django WSGI View Handler
Browser WebSocket Webserver Django ???? ??? ????
Very hard to deadlock/cause errors Seems "Django-ish" DESIGN GOALS Scales
decently All works inside runserver
Browser WebSocket Webserver Django Channels Consumers Routing
Browser HTTP Webserver Django Channels Consumer Ch. Routing View URL
dispatch
The Solution A Series Of Channels
An ordered, first-in-first-out, at-most once queue with expiry and delivery
to only one listening consumer. Identified by a unique unicode name. WHAT IS A CHANNEL?
Producers Consumers Channel
There are standard channel names: STANDARDS Clients have unique response
channels: http.request websocket.connect websocket.receive !http.response.jaS4kSDj !websocket.send.Qwek120d
There are standard message formats: STANDARDS - HTTP request -
WebSocket close - HTTP response chunk But you can make your own channel names and formats too.
But how do we do this without making Django asynchronous?
Channels are network-transparent, and protocol termination is separate from business
logic process 1 process 2 protocol server worker server channels client socket
Async/cooperative code, but none of yours process 1 process 2
protocol server worker server channels client socket Your logic running synchronously worker server
For runserver, we run them as threads thread 1 thread
2 protocol server worker server channels client socket worker server thread 3 process 1
A view receives a request and sends a single response.
WHAT IS A CONSUMER? A consumer receives a message and sends zero or more messages.
EXAMPLE This echoes messages back: def ws_message(message): text = message.content['text']
reply = "You said: %s" % text message.reply_channel.send({ 'text': reply, })
EXAMPLE This notifies clients of new blog posts: def newpost(message):
for client in client_list: Channel(client).send({ 'text': message.content['id'], })
EXAMPLE But Channels has a better solution for that: #
Channel "websocket.connect" def connect(message): Group('liveblog').add( message.reply_channel) # Channel "new-liveblog" def newpost(message): Group('liveblog').send({ 'text': message.content['id'], })
EXAMPLE And you can send to channels from anywhere: class
LiveblogPost(models.Model): ... def save(self): ... Channel('new-liveblog').send({ 'id': str(self.id), })
EXAMPLE You can offload processing from views: def upload_image(request): ...
Channel('thumbnail').send({ 'id': str(image.id), }) return render(...)
EXAMPLE All the routing is set up like URLs: from
.consumers import ws_connect routing = { 'websocket.connect': ws_connect, 'websocket.receive': 'a.b.receive', 'thumbnail': 'images.consumers.thumb', }
EXAMPLE The HTTP channel just goes to the view system
by default. routing = { # This is actually the default 'http.request': 'channels.asgi.ViewConsumer', }
The Future What does it all mean?
WSGI
WSGI 2?
ASGI channels.readthedocs.org/en/latest/asgi.html
channel_layer.send(channel, message) channel_layer.receive_many(channels) + message standards + extensions (groups, stats)
Daphne HTTP/WebSocket ASGI server asgiref Memory layer, conformance suite, WSGI
adapters asgi_redis Redis-based channel layer
Raw ASGI app example: while True: channel, message = layer.receive_many(
["http.request"], block = True, ) if channel is None: continue layer.send( message['reply_channel'], { 'content': 'Hello World!', 'status': 200, } )
Django 1.10
Django 1.10 And 1.8, 1.9 as a third-party app
It's all optional. No need to change anything if you
don't want to use channels.
pip install channels channels.readthedocs.org
Thanks. Andrew Godwin @andrewgodwin