On Sat, 2007-06-09 at 14:52 +0000, Henrik Lied wrote: > Hi there! > > I haven't found anything on this, so I thought I'd ask: > Has anyone implemented event-based caching in Django? > > Hypothetical scenario > ------------------------------- > A rather large social networking site uses memcached for caching. The > Django Caching Framework only allows time-based caching: > 1. User A logs in > 2. User A updates a blog post > 3. User B shortly after reads the blog post, but the caching framework > still displays the old version of the entry. > > -------- > How can I prevent this? Is there an easy way to delete a single key in > the cache?
Deleting a single key is easy -- have a look at the low-level API section in the caching docs. The hard part is working out which key(s) you want to delete. Since the keys used by the caching middleware are generated from request URI and headers, you would need to be able to work out all the possibilities and invalidate them individually. So, if you are just using the caching middleware, the pragmatic answer is "don't try to do this". It is implicit in the caching middleware setup that pages may be up to N minutes out of date, so user B just has to wait a little longer before seeing the updated information. If you want finer grained control, don't use the caching middleware (or don't use it solely) and cache the information you want directly, using the low-level API. Then you can retrieve the cached info fairly easily in your view to reconstruct the response and also invalidate the right pieces when they are updated. This takes a bit more work, but that makes sense, since you are wanting very fine-grained control in this sort of setup. Regards, Malcolm --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
