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

.. code-block:: bash

   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)

.. code-block:: javascript

    $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