Effortless real time apps in Django

Aaron Bassett @aaronbassett slides - https://speakerdeck.com/aaronbassett/effortless-real-time-apps-in-django

• 1996 - iframes - can refresh part of web page
• ajax - do polling request
• long polling - open request, keep open until something to say, then start new request
• all are HACKY
• 2010 - websockets - effortless real time apps
• short polling - 100000 users poll every system, 871 byte header -> 83MB per second
• websockets - 0.2 MB per second
• also save data for mobile users
• http://swampdragon.net python package
• uses django, tornado and redis
• redis is in-memory key value store, can also write to disk, pubsub built in
• tornado - python, non-blocking webserver
• django
• browser - tornado - redis - swampdragon/django - postgres
• build another todo app

pip install swampdragon
apt-get install redis  # or brew - but windows not supported, use VM, cloud ...

• swamp dragon has dragon admin, similar to django-admin.py, createproject command with standard structure
• adds settings to settings.py and creates server.py - similar to manage.py, but runs tornado server
• in production, do some WSGI thing
• Code - swampdragon.models.SelfPublishModel - mixin, when model saved, push object to redis
• uses serializers, convert python object to json, so browser can consume it
• swampdragon.serializers.model_serializer - then subclass it for your model
• can feel similar to django-rest-framework - but not quite interoperable, branch of swampdragon supports DRF serializers
• then have routers, analagous to views, swampdragon.route_handler.ModelRouter
• methods - get_list, create, delete, get_object ...
• use Angular.js for browser (but can use any other js framework, or raw js if you want)

   $dragon.subscribe('todo-item', $scope.channel, {todo_list__id: 1})
   $dragon.getList('todo-item', ...)
   $dragon.onReady(function() {
       $dragon.subscribe(...);
       $dragon.getList(...);
       $dragon.getSingle(...);
   });

   $dragon.onMessageChannel(
       ...
   );

code at https://github.com/aaronbassett/djangocon-swampdragon

• more complexity - more things to manage/go wrong
• so use PaaS - firebase, pusher, pubnub ...
• DaaS (database as a service)

http://www.leggetter.co.uk/2013/12/09/choosing-realtime-web-app-tech-stack.html

• Using Pusher instead - rewrite the SelfPublishModel - don’t need Router then
• Can use pusher angular library

https://github.com/aaronbassett/djangocon-pusher

• Working on stuff for Glasgow Council
• requirement is to see when someone else is trying to edit thing at same time as you
• only want to see notifications for single object - so create per-object channels

created django-pusherable package - on pypi and github