django-last-modified is a collection of Django middleware to help manage your caching setup.
If you're familiar with the following HTTP headers:
You can probably skip down to "Installation."
Otherwise, you can find a primer on HTTP caching located in "introduction.rst" in this repository.
- $ pip install django-last-modified
- Add CacheControlMiddleware and LastModifiedMiddleware to MIDDLEWARE_CLASSES.
CacheControlMiddleware adds the Cache-Control and Expires headers to outgoing responses while LastModifiedMiddleware adds the Last-Modified/ETag header and performs the If-Modified-Since/If-None-Match checking.
Here's a recommended MIDDLEWARE_CLASSES order:
MIDDLEWARE_CLASSES = ( 'django.middleware.common.CommonMiddleware', 'django.contrib.sessions.middleware.SessionMiddleware', 'django.contrib.auth.middleware.AuthenticationMiddleware', 'last_modified.middleware.LastModifiedMiddleware', 'last_modified.middleware.CacheControlMiddleware', # ... snip ... )
If a request is authenticated (i.e., the user has logged in) the If-Modified-Since checking is skipped.
django-last-modified doesn't need to be added to INSTALLED_APPS.
- String path to a function (e.g., 'path.to.module.function') that is called to obtain the "last modified" value. Must return either a datetime/date object or a UNIX timestamp. Default: None, must be defined.
- Number of seconds stored representation is considered fresh for private caches. Default: 3600 seconds (one hour).
- Same as CACHE_MAX_AGE but for public caches. Default: Value of CACHE_MAX_AGE.
- DISABLE_CACHE_CONTROL_MIDDLEWARE, DISABLE_LAST_MODIFIED_MIDDLEWARE
- Set to True to disable the respective middleware from being applied. Provided so you can toggle middleware off/on without having to tweak MIDDLEWARE_CLASSES. Default: False.
Django has two features like this, but they're slightly different.
The update and fetch cache middleware sets the Cache-Control, Expires, and Last-Modified headers but in the process also stores the generated pages in the server-side cache. The project I was working on had many thousand "long-tail" pages that I didn't want/need polluting any caches.
There's also "conditional view processing" which is even closer to what I needed, but can only be applied on a per-view basis while I needed the whole site covered.
In a nutshell, I wanted the whole site covered (like the cache middleware does) but only generating HTTP headers and not involving the server-side cache (like the conditional view processing).
Unable to find an existing app to do this, django-last-modified was born.