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

[Miles Waller]

Jens Vagelpohl wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> 
> On 17 Dec 2006, at 18:52, Dieter Maurer wrote:
> 
>> The description indicates in what direction the CPM should get fixed:
>>
>>   * If the response already provides cache control, the CPM should
>>     not override it, as it is likely that the specific information
>>     available to the response generating process is more trustworthy
>>     then the general CPM policies.
>>
>>     This is arguable, especially as it changes the current behaviour.
>>     Maybe, it should be controlled by an additional configuration  
>> option.
> 
> 
> 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.

At the moment, the CPM fires after rendering, so setting it's own 
headers and overwriting any headers set in the template.  If it fired 
before rendering, then a template would be free to set whatever policy 
it wanted.

Is there a special reason why it needs to set the headers after 
rendering, rather than before?  I can't think of a reason, but then our 
policies are about as simple as can be.

Miles