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From Stuart Roebuck <>
Subject Re: [RT]: Calculating the cache key
Date Wed, 22 May 2002 09:36:03 GMT

On Tuesday, May 21, 2002, at 04:28 PM, Sylvain Wallez wrote:

> Geoff Howard wrote:
>> The performance of key comparison is especially important for high 
>> traffic
>> sites (like ours).  An idea I've had to decrease this importance is:
>> An *option* to have the pipeline do asynchron cache validation - if a 
>> cached
>> item exists, use it *then* check it's validity (or cause it to be 
>> checked)
>> and remove it from the store if it was expired.  This is attractive to 
>> us
>> because we'll have many steps that will need to be checked (many of our
>> pages will involve 5 or 6 or more generators aggregated and included) 
>> and
>> the performance hit of generating and comparing all those keys is 
>> scary.
>> This integrates well with the external cache validity concept that 
>> Marcelo
>> Ochoa/DBPrism has been working on.
> Geoff, this a really good use case for the need of per-pipeline choice 
> of the pipeline implementation, which has been discussed some time ago :
> - webapp pipelines *must* use up-to-date content (i.e. cache validity 
> is always checked, or no cache is used at all)
> - content publication pipelines don't need to be checked synchronously 
> at each request, and the cache can be checked either periodically or 
> through external triggers.
> So we end up with 3 main types of pipelines :
> - non-caching,
> - caching and synchronously validated,
> - caching and asynchronously validated.
> Thoughts ?

My only concern here is that publications don't need to be checked 
synchronously for general use, but they may need to be checked 
synchronously as part of implementing a content management system for 
people who are accessing the content immediately after a change.


            Public Key - 1024D/88DD65AF 2001-11-23 Stuart Roebuck (Adolos)
      Key fingerprint = 89D9 E405 F8B1 9B22 0FA2  F2C1 9E57 5AB1 88DD 65AF
Stuart Roebuck                        
Systems Architect                             Java, XML, MacOS X, XP, 
ADOLOS                                           <>

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