[OSGeo-Discuss] The state of WMS tile caching

[Christopher Schmidt]

On Tue, Nov 25, 2008 at 09:30:35AM -0500, Alexandre Leroux wrote:
> 
> Hi list,
> 
> I have a rather simple question about the state of WMS tile caching. The 
> wiki pages content is mostly one or two years old now:
> http://wiki.osgeo.org/wiki/WMS_Tile_Caching
> http://wiki.osgeo.org/wiki/WMS_Tiling_Client_Recommendation
> 
> I took a look at
> http://www.tilecache.org/ and
> http://geowebcache.org/trac
> but wasn't able to confidently answer my question.
> 
> Can WMS tiles be cached by the server for any WMS client and still serve 
> WMS according to the standard?

TileCache does not support this. However, what some people (including
myself) have done is:
 
 * Set up a Layer to be served via WMS (GeoServer, for example)
 * Set up a TileCache in front of it
 * Set up a MapServer in front of it, using GDAL's WMS-C support:
    http://gdal.org/frmt_wms.html

Then, a request from a client like OpenLayers can go directly to the
TileCache, while a request from a 'normal' WMS client can go to the
MapServer layer which pulls from the cache.     

However, I would not recommend this technique if you expect heavy load
-- the restriction of tilecache to not do stitching is somewhat
intentional. (Enough people complain about it being slow without ading
in intentional slowdowns!)


Regards,
-- 
Christopher Schmidt
Web Developer