Image Caching, when to update?

Arnulf Christl arnulf.christl at CCGIS.DE
Thu Aug 4 11:00:12 EDT 2005

Kyle Mulka wrote:
 > I looked into squid and realized that thing it needs to know is when
 > the content changes so that it can refresh the cache. From what I've
 > heard so far, it doesn't sound like mapserver has any clue as to
 > when the map it serves might change. It seems that it would be
 > pretty easy for mapserver to simply determine if a map would change
 > based on the timestamp on the shapefiles its serving and either
 > the timestamp or the content of the map file.

Kyle Mulka wrote:
> Would it be good to move this discussion to mapserver-dev?

Hmmm, i'd say leave them out front, they got enough on their hands doing 
a great job serving maps (not that i would repeat myself... :-)

>>By the looks of what i have seen in your demo you do a great job already.
> :-)
> I'm using the PEAR Cache_Lite package for PHP right now. Its simple to use.
> Only takes about 10 lines of code.


> Exactly. This is why we need at least something in mapserver that knows
> about caching. Mapserver doesn't actually have to do the caching, but should
> know when caching would be appropriate.

I don't think any WMS service really knows a lot about what kind or 
actuality of data it actually serves (someone enlighten us?).

Wouldn't this be something that metadata could be used for? Not that 
anybody would care to provide for good metadata...

There are not too many thoughts about misusing metadata for this kind of 
job as far as i know but basically it would fit in nicely?! This said we 
might haul this discussion over to the OpenSDI clan instead of bullying 
the mapserver dev guys, but maybe we should just let them decide for 


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