Implementing real time web applications with Django

Djangocon 2012

Transcript

1. Implementing real time web applications with Django Kristian Øllegaard 1 onsdag den 6. juni 12
2. @oellegaard github.com/KristianOellegaard About me • Software Developer/System Administrator at Divio • Django since 0.96 • Danish, lived in Zurich 1,5 year 2 onsdag den 6. juni 12
3. @oellegaard github.com/KristianOellegaard Why real time? • Better user experience • More options in front end • Make the web feel like native apps • Showing live data. • Collaboration is much easier. 3 onsdag den 6. juni 12
4. @oellegaard github.com/KristianOellegaard Finding the right tool • Criteria's • Use websockets, but have fallbacks • Good browser support (incl. old IE) • Should be usable from python • Does not require extensive changes in frontend • “As fast as it can be” 4 onsdag den 6. juni 12
5. @oellegaard github.com/KristianOellegaard The tools you want Node.js + Socket.io 5 onsdag den 6. juni 12
6. @oellegaard github.com/KristianOellegaard The tools you want Node.js + Socket.io (well, we don’t want this, but socket.io needs it) 5 onsdag den 6. juni 12
7. @oellegaard github.com/KristianOellegaard The tools you want • Node.js • Built on Chrome's JavaScript runtime • Uses an event-driven, non-blocking I/O model • Socket.io • One interface for all transport methods (sockets, polling, etc.) • Compatible with almost everything 6 onsdag den 6. juni 12
8. @oellegaard github.com/KristianOellegaard Why not implement it in Python? • Already active community • Can be used from python without too much trouble • Most people know very basic javascript • More importantly, frontend engineers, knows javascript and can therefore contribute to the different browser-specific implementations. 7 onsdag den 6. juni 12
9. @oellegaard github.com/KristianOellegaard Using redis for cross-language communication • Support for many datatypes • Can be used both as storage and as a queue • Implemented in many different languages • For the usage in this talk, any other queue could have been used as well. 8 onsdag den 6. juni 12
10. @oellegaard github.com/KristianOellegaard Basic concept • Something happens, the user must be notified in real time • From e.g. django we insert the new value into the queue • Node.js listens on the queue and emits any content directly to the browser via socket.io • This is btw. very fast! Redis Django Node.js E.g. Celery Browser publish subscribe publish subscribe 9 onsdag den 6. juni 12
11. @oellegaard github.com/KristianOellegaard Sample node.js app var io = require('socket.io').listen(8001); var redis = require('redis').createClient(); redis.psubscribe("socketio_*"); // Could be any pattern io.sockets.on('connection', function (socket) { redis.on('pmessage', function(pattern, channel, key){ socket.emit(channel, key); }); }); 10 onsdag den 6. juni 12
12. @oellegaard github.com/KristianOellegaard Sample HTML/JS <script src="http://localhost:8001/socket.io/socket.io.js"></script> <script> var socket = io.connect('http://localhost:8001/'); socket.on('socketio_news', function (data) { console.log(data); }); </script> 11 onsdag den 6. juni 12
13. @oellegaard github.com/KristianOellegaard Sample usage from Python import redis import json redis_subscribe = redis.StrictRedis() redis_subscribe.publish("socketio_news", json.dumps({ 'title': 'Djangocon 2012', })) 12 onsdag den 6. juni 12
14. @oellegaard github.com/KristianOellegaard Short demo 13 onsdag den 6. juni 12
15. @oellegaard github.com/KristianOellegaard Hosting socket.io • Nginx does not support websockets! • Needs its own app, if hosted on an application cloud (e.g. heroku) • Recommended to expose the node server directly • But hey, it’s node.js, it scales! 14 onsdag den 6. juni 12
16. @oellegaard github.com/KristianOellegaard Can I use this today? • Yes • But, please don’t 15 onsdag den 6. juni 12
17. @oellegaard github.com/KristianOellegaard Client Authentication • Socket.io handles authentication from node -> client • Currently no authentication between django and node. • Could possibly be solved by storing your sessions in redis and checking them on connection. 16 onsdag den 6. juni 12
18. @oellegaard github.com/KristianOellegaard Notes • Concept should work with any language/framework • E.g. communicating between ruby and python 17 onsdag den 6. juni 12
19. @oellegaard github.com/KristianOellegaard Questions? http://kristian.io @oellegaard 18 onsdag den 6. juni 12