On Tue, Nov 13, 2007 at 10:16:38AM -0700, Ben Tuttle wrote: >> I think the silence is an indication that there is no way to ask >> MapServer to produce an exception in this case at the moment. >> I'd suggest you file a ticket proposing that as an enhancement. > Given that mapserver can't do this at the moment have you considered > other options?
Yes, I have, and I do have options. One of the things I've noticed is that I can actually get mapserver to generate an error. I just have to get the remote WMS server to generate a broken reply. If the remote WMS returns anything other than application/vnd.ogc.se_xml, mapserver will try to load it as an image. If it isn't an image, mapserver will fail, and return a proper exception. This will actually take care of most of the situations. But mapserver will still generate blank images if it's unable to contact the remote WMS or if it returns any other HTTP status than 200. > While it probably not as efficient you might be able to set up a > cron to watch your cache for new images and do a "gdalinfo -mm" on > each new tile in the cache and delete tiles with only one value (ie > blank tiles). As Daniel said, this won't work, since blank images can be valid as well. In this particular case, the remote WMS-server serves weather data. Precipitation, to be exact. So, if there's no rain or snow in an area, the response will be a blank image. Right now, the simplest solution seems to be to not fetch the weather data through mapserver. Just get the client to fetch the data directly from the other WMS-server. The only problem is that this server doesn't generate transparent images, so I'll need to hack on it a bit to add this functionality. -- Trond Michelsen
