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
730
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
330
Django Through The Years
andrewgodwin
0
220
Writing Maintainable Software At Scale
andrewgodwin
0
450
A Newcomer's Guide To Airflow's Architecture
andrewgodwin
0
370
Async, Python, and the Future
andrewgodwin
2
680
How To Break Django: With Async
andrewgodwin
1
740
Taking Django's ORM Async
andrewgodwin
0
740
The Long Road To Asynchrony
andrewgodwin
0
680
The Scientist & The Engineer
andrewgodwin
1
780
Other Decks in Programming
See All in Programming
詳しくない分野でのVibe Codingで困ったことと学び/vibe-coding-in-unfamiliar-area
shibayu36
3
4.6k
ポスターセッション: 「まっすぐ行って、右!」って言ってラズパイカーを動かしたい 〜生成AI × Raspberry Pi Pico × Gradioの試作メモ〜
komofr
0
1.1k
ネイティブ製ガントチャートUIを作って学ぶUICollectionViewLayoutの威力
jrsaruo
0
140
私達はmodernize packageに夢を見るか feat. go/analysis, go/ast / Go Conference 2025
kaorumuta
2
500
Things You Thought You Didn’t Need To Care About That Have a Big Impact On Your Job
hollycummins
0
180
開発生産性を上げるための生成AI活用術
starfish719
1
200
階層構造を表現するデータ構造とリファクタリング 〜1年で10倍成長したプロダクトの変化と課題〜
yuhisatoxxx
3
940
LLMとPlaywright/reg-suitを活用した jQueryリファクタリングの実際
kinocoboy2
4
680
『毎日の移動』を支えるGoバックエンド内製開発
yutautsugi
2
210
CSC305 Lecture 03
javiergs
PRO
0
240
タスクの特性や不確実性に応じた最適な作業スタイルの選択(ペアプロ・モブプロ・ソロプロ)と実践 / Optimal Work Style Selection: Pair, Mob, or Solo Programming.
honyanya
3
150
Conquering Massive Traffic Spikes in Ruby Applications with Pitchfork
riseshia
0
150
Featured
See All Featured
How to Ace a Technical Interview
jacobian
280
24k
Building Adaptive Systems
keathley
43
2.8k
Dealing with People You Can't Stand - Big Design 2015
cassininazir
367
27k
実際に使うSQLの書き方 徹底解説 / pgcon21j-tutorial
soudai
PRO
189
55k
Into the Great Unknown - MozCon
thekraken
40
2.1k
Building a Scalable Design System with Sketch
lauravandoore
462
33k
How GitHub (no longer) Works
holman
315
140k
Optimising Largest Contentful Paint
csswizardry
37
3.4k
Git: the NoSQL Database
bkeepers
PRO
431
66k
Rails Girls Zürich Keynote
gr2m
95
14k
Making the Leap to Tech Lead
cromwellryan
135
9.5k
Statistics for Hackers
jakevdp
799
220k
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