In Django 1.3 alpha 1, does the built-in web server cache pages (or database results) more aggressively than before?

I’m using Django version 1.3 alpha 1 (SVN-14750) to build a Django site.

I’ve got a couple of pages which display data, and allow me to edit that data. However, I seem to have to restart the built-in Django web server to see the updated data.

I don’t remember having this problem before: usually a CTRL + F5 refresh in the browser would do it. Obviously, it’s quite annoying behaviour during development, seeing up-to-date data load slower is preferable to seeing out-of-date data load instantly.

I’m using Firefox with the cache disabled (about:config, network.http.use-cache=False), so I’m reasona开发者_Go百科bly sure the issue is with Django.

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Web servers themselves don't do caching. It is up to the application itself to decide how (server-side) caching works. In Django's case, there are a number of options for enabling caching.

The high level though, is that Django sees a request for an URL, generates the html string in response, and stores that string in memory (or a database - depending on the cache backend you set). The next time a request comes through for that same URL, Django will check to see if that response lives in the cache, and if it does, will return that string. If it doesn't, the process repeats.

The idea behind providing @vary_on decorators, is that you change the lookup keys for finding a response in the cache. If you vary_on(user, url). the algorithm goes something like this:

1. request /users/3/Josh
2. key = str(user) + str(url)
3. response = get_from_cache(key)
4. if response is None: response = view_function()
5. save_to_cache(key, response)
6. return response 

The web server has no input into this type of caching.

The other type of caching is client side. This is where the web server is configured to return certain headers for specific types of resources like static content (javascript, images etc). The browser can then analyze those headers, and decide to request the content, or to use the content stored client side. This generally doesn't apply to dynamic content however.

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Ah — I still had some cache middleware enabled. Removing the following from my MIDDLEWARE_CLASSES setting in settings.py fixed it.

'django.middleware.cache.UpdateCacheMiddleware',
'django.middleware.cache.FetchFromCacheMiddleware',

(As is probably evident from the question and this answer, I don’t understand caching, Django or otherwise, very well.)