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Domain sharding in Django

It's 2015. Static files should be served by a CDN. Period. This has several advantages, the most obvious being:

  • it frees up the resources of your main server, both in bandwidth and CPU terms
  • since requests to CDN assets are on a different domain, the browser doesn't have to send (useless) cookies with every request
  • most CDN providers have datacenters all over the world to make your site more faster for more users.

In this article, we are going to look at domain sharding, an additional trick to speed up loading of media-heavy sites.

Why more is more

Once upon a time, when broadband was far on the horizon, browsers used to have a tight ceiling on the maximum numbers of concurrent requests to a single domain (around 2). These days the situation has improved, and mainstream browsers have pushed this limit up to around 7-8. However, there's still room for improvement by letting browsers load assets from different domains, thus lifting the actual global connection limit and having your media downloads saturate the user's connection.

Doing it in Django

While not part of the many batteries included with Django, sharding of media files is pretty easy to implement. There's actually a project on Github with a nice implementations a a custom Storage. Unfortunately, I had some issues when using it other 3rd party modules. Anyhow, I'm posting a slightly revised version which is friendlier and uses inheritance on the __init__ function.

As a side note, I'm also using the easy_thumbnails module for, you guessed it, thumbnails, and also had to set the THUMBNAIL_DEFAULT_STORAGE variable in settings.py to make sharding work for images.

Mobile, be aware

Some recent articles suggest that excessive reliance on domain sharding may actually be detrimental for mobile users due to the behaviour of mobile networks. Have a look here if your website has many visitors on 3/4G networks.

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