[MS4W-Users] Parallelism in KaMap - an Apache and Php/Mapscript configuration question

[Jeff Dege]

I'd never considered using the PHP command line. 

I'll give it a try.

-----Original Message-----
From: ms4w-users-bounces at lists.maptools.org [mailto:ms4w-users-bounces at lists.maptools.org] On Behalf Of Julien-Samuel Lacroix
Sent: Monday, November 01, 2010 11:20 AM
To: ms4w-users at lists.maptools.org
Subject: Re: [MS4W-Users] Parallelism in KaMap - an Apache and Php/Mapscript configuration question

Hi,

We did something similar, but on a Linux server. The only thing from your setup that seems different from ours (apart from the Windows OS), is that you call Apache. In our setup, we called the the precache script directly from the command line and we were not going through Apache at all. In the end that was the easiest way to do parallelism and it worked like a charm.

I'm not sure that's the source of your problem, but removing the Apache layer will probably help.

Hope that helps,
Julien

On 10-10-29 10:19 AM, Jeff Dege wrote:
> We have a legacy application that depends on a map served by KaMap - 
> which is a php module that serves cached map tiles, and which uses 
> MapServer's to create the tiles.
>
> We're using KaMap, instead of MapServer directly, because MapServer is 
> too slow in serving tiles on its own, running on Windows, with the 
> shapefiles we've been given. And, of course, the customer refuses to 
> allow us to host MapServer on Unix, and we can't restructure the shapefiles.
>
> Actually, even using KaMap, the tile generation is too slow, so to get 
> acceptable performance we need to precache the tiles. We have a 
> program that generates a series of "wget http://..../tile.php?..." 
> calls, each of which hits the php app on the Apache webserver, asking 
> for a particular tile. Php checks its disk cache, and if the tile 
> exists, it returns it. If not, it makes a call to mapscript to 
> generate the image, saves it in its disk cache, and returns the generated image.
>
> So, we kick off a batch file containing the multitude of tile 
> requests, and that still takes too long.
>
> My last attempt involved splitting the batch file into six smaller 
> batch files, and running them simultaneously. I expected that 
> simultaneous hits against the web server would result in multiple 
> worker processes, with multiple instances of PHP, and multiple 
> instances of MapServer, running in parallel. What I got suggested that wasn't true.
>
> Running the six batch files simultaneously took 37 hours to complete.
> Running just one of them took a bit over seven hours. That's way too 
> close to 1/6^th of the time for me to not think that we've got a 
> bottleneck, somewhere, and there's no parallelism happening.
>
> So, my question, in an MS4W installation of Apache, Php, and 
> MapServer/MapScript, is there some configuration setting I can change 
> to allow for the parallelism I'd expect to happen? Is it Apache that's 
> blocking simultaneous access? Php? Or MapScript? Is there anything I 
> can do to get simultaneous calls to tile.php to process in parallel?
>
> Thanks.
>
>
>
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--
Julien-Samuel Lacroix
Mapgears
http://www.mapgears.com/
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