Image Caching

[Arnulf Christl]

Kyle Mulka wrote:
> Is there any way to tell mapserver to cache the images produced by the 
> WMS service and then replay those on an identical request later to speed 
> things up significantly?

Currently there is no server side caching implemented within UMN 
MapServer. As far as i know this is not planned. Personally i think it 
should not be done. By the looks of what i have seen in your demo you do 
a great job already. :-)

> Basically, I want a mapserver backend to Google Maps. Right now, I've 
> gotten two WMS layers similar to Google's Hybrid mode. I do have caching 
> set up so that mapserver isn't being used to draw most of the tiles, but 
> I would like this functionality behind the WMS service itself instead of 
> in front.

Why that? Is it not a good idea to use whatever is best suitable for 
caching? Probably this will rather be some reliable and tested squid 
proxy set-up or any kind of front end behind which MapServer can hide. 
The job of MapServer is to serve maps - hence the name =:-). The job of 
a proxy that can cache would be just that. A similar discussion is going 
on around authentication and authorisation - there are loads of reliable 
AA services which can be wrapped around an existing service, so why 
burden this on top of MapServer. The only reason would be to minimize 
installation and maintenance efforts and those are negligible compared 
to all the rest when MapServer works in an enterprise environment.

> Here's my demo:
> _http://maps.kylemulka.com/umbuildings-onsat.php_
> 
> And another demo using Google's roads layer:
> _http://maps.kylemulka.com/umbuildings.php_
> 
> -Kyle Mulka

Cool demos, would you share the architecture on how you implemented 
caching in this installation?
In some environments (preferrably very large networks) you do not have 
to worry at all about caching because its been done by the network 
anyway. That is when we start to develop a problem the other way round - 
how to tell the caching service to request for a new tile because the 
content has changed on the server...

Best,