[MapProxy] Re: Response time question

[Oliver Tonnhofer]

Hej Johan,

On 31.03.2011, at 15:07, Johan Sandberg wrote:

> hey!
> 
> I'm measuring responses to Map Proxy when its seeded. 
> I dont get that satisfying response time as a wish. When I perform requests of a image size of 400*300, 10 request at the time I get low response time(around 50, 60ms).
> 
> When I do image size of 800*600 the response time is up to 1-2 sec.
> And even bigger image size give response time up to 5-6 sec.
> Is this normal response time when requesting seeded tiles?

MapProxy should scale linear with the number of pixels. So you should expect 1/4 requests when changing from 400x300 to 800x600. You should measure the times with one concurrent requests at first and then you should look how you can scale that with increased concurrency, see below.

> The request should be alligned with the resolution that is seeded so they don't have to re scaled.  
> How much is the normal cost in time of rescaling an image? Do the request have to be perfectly alligned with the cached resolution to achieve the low response time that I wish?

Depends on the resampling method, you have to check for your self. The performance can degrade dramatically when you request a lower resolution than your first/upper level, because it then needs to merge lots of tiles. So make sure you don't run into that.

> I have installed map proxy on a Linux computer with httpd apache server. I followed the wgsi example.

You should run mod_wsgi with multiple daemon processes when you have more than one CPU: http://code.google.com/p/modwsgi/wiki/ConfigurationDirectives

Regards,
Oliver

-- 
Oliver Tonnhofer    | Omniscale GmbH & Co KG    | http://omniscale.de
http://mapproxy.org | https://bitbucket.org/olt | @oltonn