[Zope-CMF] [Warning] Danger from Zope caching, especially the CMF Caching Policy Manager

[Dieter Maurer]

Jens Vagelpohl wrote at 2006-12-17 19:57 +0100:
> ...
>I don't know if it is possible to have any sane policy about "what to  
>do if the response already has caching headers". First of all, when  
>should this exception policy trigger? Which headers should tell the  
>CPM that someone else already decided on caching? Secondly, what is  
>the behavior supposed to be? "Do nothing"? "DWIM"? This obviously  
>needs exact specifications and use cases.

The HTTP/1.1 specification tells us what cache-control headers are for
and we can deduce from it how to merge "concurrent" cache controls
when the aims of HTTP/1.1 are respected (ensure "semantic transparency").

I sketched this in the collector issue.

> ....
>>   * The CPM (and Zope's HTTP Cache Manager) must set cache headers
>>     only based on the object that generated the (complete) response
>>     entity and not based on other objects called during the request
>>     (and probably only responsible for part of the entity).
>
>As mentioned in my reply to your collector issue, there are fixes on  
>the CMF trunk already and you should look at those to see if they fix  
>your problem.

As I replied in the collector: I improves the state of affairs a lot
but it still only a partial solution...



-- 
Dieter