[OSM-dev] rendering: mad ideas

[Erik Johansson]

On 3/24/06, Mikel Maron <mikel_maron at yahoo.com> wrote:
> The last time I was investigating this, things got stuck with Squid. I was trying to implement cache invalidation on a list of cache objects, using the squidpurge tool, and it wasn't working brilliantly. Help welcome.

What was the problem? I have to date had no problem with invalidating
my very very very simple test pages (just ordinary CGIs without
changing the URLs)..

I got a nice tip from Henrik Nordström of Squid fame, if you add a
header to the request  you can tell squid to only give to the image if
it is cached. Very usefull, and perhaps a good idea to use in the
applet..

Cache-Control: only-if-cached

Compare:
# noncached tile
wget --header "Cache-Control: only-if-cached"
'http://tile.openstreetmap.org/cgi-bin/steve/mapserv?map=/usr/lib/cgi-bin/steve/wms.map&service=WMS&WMTVER=1.0.0&REQUEST=map&STYLES=&TRANSPARENT=TRUE&LAYERS=landsat,streets&WIDTH=256&HEIGHT=128&BBOX=17.841873,59.332920536311434,17.929764,59.39'

# cached tile
wget http://tile.openstreetmap.org/cgi-bin/steve/mapserv?map=/usr/lib/cgi-bin/steve/wms.map&service=WMS&WMTVER=1.0.0&REQUEST=map&STYLES=&TRANSPARENT=TRUE&LAYERS=landsat,streets&WIDTH=256&HEIGHT=128&BBOX=17.841873,59.332920536311434,17.929764,59.355327237805916

--
/Erik