A talk examining the state of WebSockets in Django; showcasing several techniques for incorporating WebSockets in your Python web app.

1. The State of WebSockets in Django
Rami Sayar - @ramisayar
Technical Evangelist
Microsoft Canada

2. Agenda
• Where is WebSockets right now?
• Where is Socket.IO?
• Where does Django fit in?
• Using Django SwampDragon.
• Using Gevent.
CONFOO - @RAMISAYAR

3. Assumptions
• Working knowledge of Django, JavaScript & Python.
Note: Slides will be made available.
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4. What is a production web app?
• Django is surrounded by tons
of applications, services and
code in production.
• Advanced Django architecture
is needed to support Django
in production without failing
hard.
• WebSockets falls apart from
the rest.
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5. WebSockets
• “WebSocket is a protocol for
full-duplex communication
channels over a single TCP
connection.” Wikipedia
• Image Reference
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6. WebSockets
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7. Socket.IO
• “Socket.IO enables real-time
bidirectional event-based
communication. It works on
every platform, browser or
device, focusing equally on
reliability and speed.”
Reference
• Use by everyone: Microsoft
Office, Yammer, Zendesk,
Trello, etc…
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8. Socket.IO Version 1.0 is here!
Technically, now at v1.3.4
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9. Python, Django & WebSockets.
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10. Python and WebSockets
• Python and WebSockets has notoriously been very difficult.
• Two reasons:
• WSGI protocol does not support WebSockets. Most popular form of
web request handling in the Python web apps. Most frameworks are
designed for use with FastCGI or mod_wsgi, etc.
• Default Python networked apps not exactly designed for event-based
communication, you have to use things like gevent and twisted/tornado.
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11. Django & WebSockets
• Django applications complete HttpResponses.
• Django not well suited for WebSocket event handling structure
nor the channel approach in Socket.IO.
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12. Presenting 3 Methods for WebSockets in Django
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13. gevent
• “gevent is a coroutine-based Python networking library that
uses greenlets to provide a synchronous API on top of the libev
event loop.”
• Event loop based on libev (same as Node.js)
• Lightweight execution units, a.k.a. “lightweight threads”.
• Cooperative sockets with SSL support.
• Similar programming model to Node.js.
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14. gevent-socketio
• gevent-socketio is a pure Python implementation of the
Socket.IO protocol. Basically, it is a port of Socket.IO and
typically behind in major releases.
• Designed to work with multiple different WSGI-based web
frameworks.
• Handles the “WSGI” problem by providing a custom gevent
WSGI server for use with gevent-socketio.
• Only dependencies are gevent.
• Imperfect solution: Django is still blocking (monkey
patching is not perfect).
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15. Demo 1: Django chat engine with gevent-socketio
https://github.com/abourget/gevent-socketio/tree/master/examples/
django_chat
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16. “Native” Django Implementation
• Previous approach requires significant modifications to your
current Django app serving stack. Native as in you don’t need to
know anything besides Django.
• Building an implementation of WebSockets on top of Django.
• Identified two problems for WebSockets in Django:
• Problems with WSGI still present EXCEPT in uWSGI.
• Networked event handling model is problematic.
• Solution:
• Use Nginx which follows – event-driven async architecture.
• uWSGI & Gevent for event handling.
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17. Django-WebSocket-Redis
• Module implements websockets on top of Django.
• Use Redis as a data store for messaging behind uWSGI and Nginx.
• Runs a separate Django main loop in a cooperative concurrency
model using gevent -> 1 thread for all open websockets.
• Django can be started as usual with ‘./manage.py runserver’.
• Normal requests communication with separate main (websocket)
loop through Redis.
• Read:
Offloading Websockets and Server-Sent Events AKA “Combine
them with Django safely”
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18. Demo 2: Django-WebSockets-Redis
https://github.com/jrief/django-websocket-redis
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19. SwampDragon
• New project that adds websocket support
• Self-publishing models
• Django ORM Style Data Filter for Subscription Channels –
Similar to WebSockets + Data Filter
• Relies on Redis for messaging + Tornado
• Angular JS Support
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20. Demo 3: Django Swampdragon
https://github.com/jonashagstedt/swampdragon
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21. On Redis
• Redis is extremely popular as an easy and simple publish-
subscribe.
• Redis is very particular about memory. Running out of memory
in Redis -> CRASH AND BURN!
• If you don’t have enough memory in your VM to run Redis
Cache -> Change your approach, use Apache Kafka.
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22. What did we learn?
• The State of WebSockets in Django.
• Django and WebSockets is not impossible.
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23. Thank You! Questions?
Follow @ramisayar
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24. Resources
• http://swampdragon.net/
• http://django-websocket-redis.readthedocs.org/en/latest/
• https://github.com/jrief/django-websocket-redis
• https://github.com/abourget/gevent-socketio/tree/master/
examples/django_chat
• http://jpadilla.com/post/74391616727/the-easiest-way-to-add-
websockets-to-django
• http://ferretfarmer.net/2013/09/05/tutorial-real-time-chat-with-
django-twisted-and-websockets-part-1/
CONFOO - @RAMISAYAR

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