id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
35465	Feature: allow pre-caching and disable-cache	Julien Palard	nobody	"TL;DR: If there was a way to inhibit `cache.get()` (making it to always return `default`), it would enable to use cases :

- One could implement a pre-caching tool like a simple curl in a crontab.
- One could implement a ""disable cache"" feature like the one in browsers network panel, but applied server-side.

Longer explanation:

My initial idea is was to prefill the cache (say template fragments) using a cron to guarantee cache hits for humans.

In the current Django, I can't do it: the cron would often just cache hit, doing nothing, and a random human will cache miss and have a slower request.

So I think I need a way to tell ""if it's the pre-caching cron, don't try to 'get' from the cache, just compute everything slowly, and fill the cache with fresh data'.

And for this to work I « just need » to replace the real get during the pre-caching step with:

    def get(self, key, default=None, version=None):
        return default

For example, if I have a 15mn cache with a 10mn cron, the cache will never be close to expire, and it would be impossible for a user to cache miss.

Once this implemented, it could be ""reused""/""recycled"" as a ""disable-cache"" feature: say for example the Django Debug Toolbar could have a checkbox ""disable cache"", it would have the strange side effect to populate the cache, but it would work as expected: the presented data would be fresh.

Say we're going this way, it would need for a way to tell ""this request is without cache"", like a cookie, a query string parameter, or whatever fits in an HTTP request. If there's no concensus on how to flag this ""cache disabled"" behavior it could be implemented as a dotted path to a function returning a boolean, as SHOW_TOOLBAR_CALLBACK from Django debug toolbar.

There's a ""security"" catch to be aware of: if it's too easy to disable cache on production servers, like `?cache=no` it could be used to DoS, it probably has to be a tad more secure like by using a secret.

I have not tried to implement it, I'd like to discuss it before, so: does it looks like a good idea? Has it been discussed many times before that I missed maybe?"	New feature	new	Core (Cache system)	5.0	Normal		cache	Julien Palard	Unreviewed	0	0	0	0	0	0