[drupal-devel] caching issues

Steven Wittens steven at acko.net
Wed Mar 9 04:16:27 UTC 2005

>Thoughts?  Feedback?  Suggestions?  Dries?
Dries and I did a bunch of cache tests a while ago, the conclusions were 
posted on the list. I think it was shortly after the 4.5 release.

Various ideas for keeping the cache alive longer were posted as well. 
Ones I can remember:

- Enforcing a minimum cache lifetime for pages is pretty easy with the 
timestamp/expiration parameter for cache.

- It is important that a user sees his/her changes reflected 
immediately, otherwise they might think an error occured and post twice. 
Possible solution: disable caching for a user's session as soon as a 
they have posted something. For your case this would mean the spambot 
get fresh pages all the time, but the rest doesn't.

- Clearing the cache selectively is difficult because sidebar blocks 
like "active forum topics" change easily. Still, clearing out the "main" 
page for a certain item (e.g. a node view) is doable.

- The cache has a much higher miss rate than expected on drupal.org at 
least because the site is constantly being crawled by spiders. Pages 
that are visited often get re-cached quickly after a wipe, but this 
doesn't happen for the random access pattern that is common for spiders 
and also for posts reached through searching.

- Any aggressive caching should be implemented as an optional feature as 
it is useless for small sites. Perhaps we could change the cache option 
into three states: "No caching" "Mild caching" "Aggressive caching".

Still, it sounds to me like your problem could be fixed by imposing a 
throttle on submissions (we used to have this, but it got lost in one of 
the node system rewrites) or by trying to detect spammy behaviour and 
imposing a (temporary) ban.

If you dig around the mailinglist archive some more, you might find some 
more things.


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