[OSM-dev] WMSC - bachelor thesis

Jukka Rahkonen jukka.rahkonen at latuviitta.fi
Wed Aug 17 13:53:59 BST 2011


Hi,

WMS-C means that WMS-C capable client (such like uDig or OpenLayers) is
sending otherwise normal WMS GetMaps but with an extra parameter
&TILED=YES and strictly controlled and synchronized BBOX, WIDTH, and
HEIGHT parameters. The WMS-C capable server sends the information about
the tiling schema with the GetCapabilities response so that the client can
build reasonable requests.

If WMS-C server receives such a request it knows to seach the tile first
from the cache. It the tile is cached the response is very fast and
comparable with all the other tile server implementations that exist. If
the image is not cached the request is passed on to a normal WMS server
pipe and the speed is the same as with normal WMS.

If you want to do direct comparison of speed with direct WMS and cached
WMS-C then make sure that the WMS-C cache is populated.  Next do whole lot
of tiled requests with for example uDig and capture them from the server
cache.  Make two test request sets with the original requests and modified
requests where the &TILED=YES part is ripped off.  That way they should go
to WMS server instead of the cache. Finally run the requests with jMeter
with varying number or concurrent requests. I am not sure if such
comparison makes much sense, because typically 256x256 sized tiled
requests do not suit direct WMS usage best. But if you want to get a
result that shows that WMS-C is faster than direct WMS, this is the way to
achieve it.

I would say that GeoWebCache would be the easiest way to setup a WMS-C
server (and TMS and WMTS at the same time). WMTS is an OGC standard and
accepted to be used with Inspire view services, so why not to test it for
your thesis?

-Jukka Rahkonen-


BG wrote:
> Hej there,
>
> At the moment I am working on my bachelor thesis using osm data to
create cached-wms (wmsc).
>
> I now have a running mapnik based tirex tile-server combined with a wms
via mod_mapnik_wms. Next, I want to use the tilecache.org wmsc.
>
> I have some questions and hope to find help along my path.
>
> 1. Are there any possibilties to check the performance of a wms/wmsc? I
want to compare the server performance. I just need to see, if wmsc is
faster than wms.
>
> 2. I thought wmsc has to be faster than wms - but nobody is using it, is
there a reason?
>
> 3. I know the mod_mapnik_wms and the wmsc from tilecache.org - do u know
more or better software, which does or doesn't work mapnik based? Is
there an alternative to mapnik?
>
> 4. Is there a possibility to synchronize the database automatically,
which i need to import from osm?
>
> 5. While importing via osm2pgsql the system used 4gb ram - how much
would i need for the planet file?
>
> I would appreciate any help.
>
> Best regards,
> Bernd
>
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