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
The Long Road To Asynchrony
Search
Andrew Godwin
February 22, 2020
Programming
0
660
The Long Road To Asynchrony
My keynote from PyCon Belarus 2020.
Andrew Godwin
February 22, 2020
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
360
Async, Python, and the Future
andrewgodwin
2
680
How To Break Django: With Async
andrewgodwin
1
730
Taking Django's ORM Async
andrewgodwin
0
730
The Scientist & The Engineer
andrewgodwin
1
780
Pioneering Real-Time
andrewgodwin
0
440
Other Decks in Programming
See All in Programming
Swift Updates - Learn Languages 2025
koher
2
480
The Past, Present, and Future of Enterprise Java with ASF in the Middle
ivargrimstad
0
110
Deep Dive into Kotlin Flow
jmatsu
1
340
機能追加とリーダー業務の類似性
rinchoku
2
1.3k
知っているようで知らない"rails new"の世界 / The World of "rails new" You Think You Know but Don't
luccafort
PRO
1
160
Navigating Dependency Injection with Metro
zacsweers
3
270
請來的 AI Agent 同事們在寫程式時,怎麼用 pytest 去除各種幻想與盲點
keitheis
0
120
時間軸から考えるTerraformを使う理由と留意点
fufuhu
16
4.8k
旅行プランAIエージェント開発の裏側
ippo012
2
910
OSS開発者という働き方
andpad
5
1.7k
Navigation 2 を 3 に移行する(予定)ためにやったこと
yokomii
0
260
アセットのコンパイルについて
ojun9
0
130
Featured
See All Featured
How To Stay Up To Date on Web Technology
chriscoyier
790
250k
Measuring & Analyzing Core Web Vitals
bluesmoon
9
580
Being A Developer After 40
akosma
90
590k
XXLCSS - How to scale CSS and keep your sanity
sugarenia
248
1.3M
For a Future-Friendly Web
brad_frost
180
9.9k
Side Projects
sachag
455
43k
Principles of Awesome APIs and How to Build Them.
keavy
126
17k
The Art of Delivering Value - GDevCon NA Keynote
reverentgeek
15
1.6k
Product Roadmaps are Hard
iamctodd
PRO
54
11k
Templates, Plugins, & Blocks: Oh My! Creating the theme that thinks of everything
marktimemedia
31
2.5k
Navigating Team Friction
lara
189
15k
[Rails World 2023 - Day 1 Closing Keynote] - The Magic of Rails
eileencodes
36
2.5k
Transcript
LONG ROAD ANDREW GODWIN // @andrewgodwin ASYNCHRONY TO THE
Andrew Godwin / @andrewgodwin Hi, I’m Andrew Godwin • Django
core developer • Worked on Migrations, Channels & Async • Once a Londoner, now from Denver, USA
Andrew Godwin / @andrewgodwin
Andrew Godwin / @andrewgodwin "Asynchronous Programming" What is it, really?
Andrew Godwin / @andrewgodwin Concurrent Programming The more general term
Andrew Godwin / @andrewgodwin Input Process Output Sequential execution
Andrew Godwin / @andrewgodwin Input Process Output Process Concurrent execution
Archive
Andrew Godwin / @andrewgodwin Shared use of a single resource
In this case, CPUs
Andrew Godwin / @andrewgodwin "Communicating Sequential Processes", C. A. R
Hoare
Andrew Godwin / @andrewgodwin func main() { messages := make(chan
string) go func() { messages <- "ping" }() msg := <-messages fmt.Println(msg) }
Andrew Godwin / @andrewgodwin Multiple processes multiprocessing Threads threading Event
loops asyncio / twisted
Andrew Godwin / @andrewgodwin Multiple processes scale best It's also
difficult and costs the most!
Andrew Godwin / @andrewgodwin Threads are unpredictable Also, the GIL
is our ever-present friend
Andrew Godwin / @andrewgodwin Event loops are a good compromise
They do require shared memory, though.
Andrew Godwin / @andrewgodwin Asynchronous ≈ Event loops Most of
the time!
Andrew Godwin / @andrewgodwin # Ready when a timer finishes
await asyncio.sleep(1) # Ready when network packets return await client.get("http://example.com") # Ready when the coroutine exits await my_function("hello", 64.2)
Andrew Godwin / @andrewgodwin Network/timer updates An event loop's flow
Select a ready task Run task Add new tasks to queue await
Andrew Godwin / @andrewgodwin Coroutines Time →
Andrew Godwin / @andrewgodwin How did we get here?
Andrew Godwin / @andrewgodwin 1998 threading module, Stackless Python 2002
Twisted 2006 Greenlets (later gevent, eventlet) 2008 multiprocessing module 2012 Tulip, PEP 3156 2014 asyncio module 2005 Coroutine-friendly generators (PEP 342)
Andrew Godwin / @andrewgodwin 2017 Django Channels 1.0 2018 Django
Channels 2.0 2019 DEP 9 (Async support) 2020 Async views land in Django
Andrew Godwin / @andrewgodwin No solution is perfect Everyone chooses
different tradeoffs
Andrew Godwin / @andrewgodwin Asyncio is based on yield from
Because it was prototyped in Python 2
Andrew Godwin / @andrewgodwin Can't tell if a function returns
a coroutine! There are standard hints, but no actual guaranteed way
Andrew Godwin / @andrewgodwin async def calculate(x): result = await
coroutine(x) return result # These both return a coroutine def calculate(x): result = coroutine(x) return result
Andrew Godwin / @andrewgodwin Can't have one function service both
How we got here makes sense, but it's still annoying sometimes.
Andrew Godwin / @andrewgodwin # Calls get.__call__ instance = MyModel.objects.get(id=3)
# Calls get.__call__ # and then awaits its result instance = await MyModel.objects.get(id=3)
Andrew Godwin / @andrewgodwin You have to namespace async functions
I really, really wish we didn't have to
Andrew Godwin / @andrewgodwin instance = MyModel.objects.get(id=3) instance = await
MyModel.objects.async.get(id=3)
Andrew Godwin / @andrewgodwin Completely different libraries! Even sleep() is
different.
Andrew Godwin / @andrewgodwin time.sleep ➞ asyncio.sleep requests ➞ httpx
psycopg2 ➞ aiopg WSGI ➞ ASGI Django ➞ Django?
Andrew Godwin / @andrewgodwin Django & Async
Andrew Godwin / @andrewgodwin Asyncio only benefits IO-bound code Code
that thrashes the CPU doesn't benefit at all
Andrew Godwin / @andrewgodwin We're adding async to some parts
The bits where it makes sense!
Andrew Godwin / @andrewgodwin But, you can't mix sync and
async So we have to have two parallel request paths
Andrew Godwin / @andrewgodwin WSGIHandler __call__ WSGI Server WSGIRequest BaseHandler
get_response URLs Middleware View __call__ HTTP protocol Socket handling Transfer encodings Headers-to-META Upload file wrapping GET/POST parsing Exception catching Atomic view wrapper Django 3.0 Request Flow
Andrew Godwin / @andrewgodwin WSGIHandler __call__ WSGI Server WSGIRequest BaseHandler
get_response URLs Middleware Async View __call__ ASGIHandler __call__ ASGI Server ASGIRequest Sync View __call__ Asynchronous request path Proposed async request flow
Andrew Godwin / @andrewgodwin WSGIHandler __call__ WSGI Server WSGIRequest URLs
Middleware View __call__ ASGIHandler __call__ ASGI Server ASGIRequest Asynchronous request path BaseHandler get_response_async BaseHandler get_response URLs Middleware Async View __call__ Implemented async request flow
Andrew Godwin / @andrewgodwin We have to work with what
we have I'd rather let people ship code than argue about perfection.
Andrew Godwin / @andrewgodwin Django's main job is safety It
matters more than anything else
Andrew Godwin / @andrewgodwin Deadlocks Livelocks Starvation Race conditions
Andrew Godwin / @andrewgodwin Coroutines & the GIL actually help!
You're saved from all the awful memory corruption bugs
Andrew Godwin / @andrewgodwin async def transfer_money(p1, p2): await get_lock()
# Code between awaits is atomic! subtract_money(p1) add_money(p2) await release_lock()
Andrew Godwin / @andrewgodwin You can still screw up a
lot Trust me, I have lived it while developing async
Andrew Godwin / @andrewgodwin async def log_message(m): await client.post("log-server", m)
result = calculate_result() log_message(m)
Andrew Godwin / @andrewgodwin async def log_message(m): await client.post("log-server", m)
result = calculate_result() await log_message(m)
Andrew Godwin / @andrewgodwin Async usability has a long way
to go But it is undoubtedly the future!
Andrew Godwin / @andrewgodwin Python is the language of pragmatism
If anyone can get it right, we can
Andrew Godwin / @andrewgodwin What does the future hold? Hopefully,
no GIL!
Andrew Godwin / @andrewgodwin Let's make async understandable Almost every
project could benefit, if we made it worth their time.
Thanks. Andrew Godwin @andrewgodwin // aeracode.org