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
Pioneering Real-Time
Search
Andrew Godwin
October 03, 2019
Programming
0
450
Pioneering Real-Time
My keynote from PyCon Balkan 2019
Andrew Godwin
October 03, 2019
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
460
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
790
Other Decks in Programming
See All in Programming
CSC509 Lecture 07
javiergs
PRO
0
250
CSC305 Lecture 08
javiergs
PRO
0
280
Developer Joy - The New Paradigm
hollycummins
1
370
三者三様 宣言的UI
kkagurazaka
0
250
CSC305 Lecture 09
javiergs
PRO
0
310
AI駆動で0→1をやって見えた光と伸びしろ
passion0102
1
860
What's new in Spring Modulith?
olivergierke
1
170
品質ワークショップをやってみた
nealle
0
640
チームの境界をブチ抜いていけ
tokai235
0
230
組込みだけじゃない!TinyGo で始める無料クラウド開発入門
otakakot
2
380
Temporal Knowledge Graphで作る! 時間変化するナレッジを扱うAI Agentの世界
po3rin
1
100
SwiftDataを使って10万件のデータを読み書きする
akidon0000
0
240
Featured
See All Featured
Agile that works and the tools we love
rasmusluckow
331
21k
"I'm Feeling Lucky" - Building Great Search Experiences for Today's Users (#IAC19)
danielanewman
230
22k
Visualization
eitanlees
149
16k
Exploring the Power of Turbo Streams & Action Cable | RailsConf2023
kevinliebholz
36
6.1k
Building a Scalable Design System with Sketch
lauravandoore
463
33k
XXLCSS - How to scale CSS and keep your sanity
sugarenia
249
1.3M
Documentation Writing (for coders)
carmenintech
75
5.1k
StorybookのUI Testing Handbookを読んだ
zakiyama
31
6.2k
Git: the NoSQL Database
bkeepers
PRO
431
66k
A Tale of Four Properties
chriscoyier
161
23k
Building Adaptive Systems
keathley
44
2.8k
What's in a price? How to price your products and services
michaelherold
246
12k
Transcript
PIONEERING REAL-TIME ANDREW GODWIN // @andrewgodwin
Hi, I’m Andrew Godwin
async def view(request): data = await api_call(pk=5) return render(request, "a.html",
…)
"The Real-Time Web"
AJAX 1999 Comet 2006 WebSockets 2011
"Real-Time"
“A system in which input data is processed within milliseconds
so that it is available virtually immediately
None
None
CPU cores run one thing at a time (yes, computers
are basically a giant lie)
Program 2 Program 3 Program 1
Scheduling The art of running multiple things at once
Program 2 Program 3 Program 1 300 cycles 300 cycles
300 cycles
Program 2 Program 3 Program 1 300 cycles Restore Save
Restore Save Restore Save 30 cycles 30 cycles 300 cycles 30 cycles 30 cycles 300 cycles 30 cycles 30 cycles
Context switching is expensive The more you have, the worse
it gets
Python's threading has this problem! The more you have, the
worse it gets
Active Threads Idle Threads Runtime 1 0 1.3 seconds 1
1 2.3 seconds 1 5 5.4 seconds 1 30 39 seconds 1 100 15 minutes
"Boxcar" scheduling has… issues Don't ever write avionics software like
this! Thanks.
None
None
72kb Woven core memory
0.085 Mhz processor
“ Don Eyles ...when the guidance system was first being
conceived, the onboard software was almost an afterthought
None
None
Priority-based Executive Please do write avionics software like this.
Job Priorities Higher numbers beat lower Limited job "RAM" Only
7 running at once Interrupts from hardware Descent radar, keyboard, etc.
Predictable Software They knew exactly what ran and what it
took
...Unpredictable Hardware It's never easy, especially in space.
None
Two differently phased 800Mhz clocks This is really bad, trust
me.
False detections stole computer time The radar system had to
update the guidance computer
Descent Phase: 85% load Capsule orientation and thrust calculations Hardware
Bug: 13% Caused by the descent radar Display Routine: 5% Astronauts trying to see how far to go
103%
None
SERVICER never gets to run But the system keeps trying
to schedule it
Alarm 1202 The computer self-restarts, but keeps crashing
Buzz Aldrin works it out Turns off the display routine
to bring the load under 100%
Apollo 11 was almost a failure ...but good software design
prevented it
Apollo 9 First flight test of Lunar Module Apollo 10
Second test and partial descent of Lunar Module Apollo 11 First Moon landing
“ Eugene A. Cernan, recounting Apollo 10 Don't give those
guys an opportunity to land, 'cause they might!
Building for Failure Software is only as good as its
worst outing
“ Don Eyles During simulations we sometimes pushed the [restart]
button randomly
We often only design for the good cases After all,
that's what we're expecting to happen
Hardware is always unpredictable Disks, networks, even keyboards and mice
Can your software survive a crash? Or does it need
a clean shutdown to work?
How will you handle the unexpected? Weird input. Slow network
connections. Emoji.
“ Don Eyles When Hal Laning designed the Executive and
Waitlist system, he made it up from whole cloth with no examples to guide him. The design [...] still represents the state of the art.
All software has consequences We may not all be designing
spacecraft, but we affect lives.
doneyles.com/LM/Tales.html Tales from the Lunar Module Guidance Computer, 2004
Thanks. Andrew Godwin @andrewgodwin // aeracode.org