[mapserver-users] On-the-fly vertical assembly of disparate tilesets using MapCache?

[thomas bonfort]

On Fri, Apr 20, 2012 at 16:02, John Taranu
<jtaranu at firstbasesolutions.com> wrote:
> Hello,
>
>
>
> Is there any recommended way to do multi-tileset vertical assembly in
> MapCache?
>
>
>
> I have the following setup:
>
>
>
> There are a number (over 30) fully seeded tile caches covering adjacent but
> spatially distinct areas.  These tilesets were fully seeded down to the
> lowest level, with the seeding restricted to an irregular polygon extent.
> Areas beyond the edge of the polygon are not seeded at all.  That is, any
> tiles within the dataset’s rectangular extents but outside the polygon
> extent are not seeded.  The tilesets do not refer back to a MapServer source
> for any requests.  This means that any tile requests between the restricted
> extent and the polygon extent return a blank image and an HTTP 404 error.
>
>
>
> I am trying to serve the separate tile sets independently, but also combined
> into a single “mosaic-like” tile layer, to be rendered on the fly from the
> individual tilesets.    The current set up has the mosaic layer in the
> MapCache config as a WMS source, referencing the tile caches as individual
> layers, looping back into itself through localhost.   It looks like this:
>
>
>
>    <source name="MOSAIC_LAYER" type="wms">
>
>       <getmap>
>
>          <params>
>
>             <format>image/png</ format >
>
>             <layers>LAYER1,LAYER2,LAYER3</layers>
>
>             <transparent>true</transparent>
>
>          </params>
>
>       </getmap>
>
>       <http>
>
>          <url>http://localhost/mapcache/service</url>
>
>       </http>
>
>    </source>
This might be a setup leading to a deadlock on your webserver, if you
ever reach your maximum number of clients. The lock in the worst case
would hold until the curl getmap request initiated by mapcache times
out.

>
>
>
> The problem is that if any tile in the 30 separate cache layers is missing,
> MapCache returns a blank tile for the mosaic layer.
>
>
>
> Is there another way of configuring a combined mosaic layer in MapCache, or
> does this require updates to the code?
This would require an update to the code, to tell mapcache to return a
transparent tile on a cache miss when no source is configured for the
tileset.

cheers,
thomas

>
>
>
> Thanks,
>
>
>
> ---------------------------------------
>
> John Taranu
>
> Senior Web Developer
>
> First Base Solutions Inc
>
> 140 Renfrew Drive, Suite 100
>
> Markham, ON, L3R 6B3
>
> phone: 905-477-3600 ext. 302
>
> email: jtaranu at firstbasesolutions.com
>
> web: firstbasesolutions.com
>
>
>
>
>
>
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