Flask-CacheBust is a Flask extension that adds a hash to the URL of each static file. This lets you safely declare your static resources as indefinitely cacheable because they automatically get new URLs when their contents change.

Usage

Install Flask-CacheBust by placing the "flask_cache_bust" folder somewhere importable from Python. Import the extension and use it to augment your app:

from flask.ext import cache_bust

# ...

cache_bust.init_cache_busting(app)

The url_for function will now cache-bust your static files. For example, this template:

<script src="{{ url_for('static', filename='js/main.min.js') }}"></script>

will render like this:

<script src="/static/1fc6e32/js/main.min.js"></script>

The "1fc6e32" part will change whenever "main.min.js" changes. Now you can configure long cache expiration dates on your static files with a header like Cache-Control: max-age=31536000!

Motivation

This was originally written for www.cloudboltsoftware.com while exercising an obsession for minimizing page load time and delivering a snappy browsing experience. It improves over Last-Modified or ETag cache schemes by enabling an expiration date to be set, which removes round-trip checks to see if a browser's cached version of a resource is still valid.