django-last-modified

django-last-modified is a collection of Django middleware to help manage your caching setup.

If you're familiar with the following HTTP headers:

• Cache-Control
• Expires
• Last-Modified
• ETag
• If-Modified-Since
• If-None-Match

You can probably skip down to "Installation."

Otherwise, you can find a primer on HTTP caching located here.

Installation

1. $ pip install django-last-modified
2. 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.

Configuration

LAST_MODIFIED_FUNC

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.

CACHE_MAX_AGE

Number of seconds stored representation is considered fresh for private caches. Default: 3600 seconds (one hour).

CACHE_SHARED_MAX_AGE

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.

Doesn't Django already have this?

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.

LICENSE

MIT