[Mapserver-users] Raster Image Limitation

[Frank Warmerdam]

Rene Teniere wrote:
> Hi All,
> 
> We have a site that we want to go public (built using Chameleon because
> my coded site is not ready yet and this had to be out ASAP) that uses a
> lot of rasters (410 indexed ecw's @ 18 - 25mb each). There are 4 other
> full images at much lower resolution that are scale dependent, once you
> reach a certain scale the high res stuff kicks in. The problem is that
> it works fine with one person, when multiple people use it, it craps
> out. We tested it out and it seems that it can only handle four high res
> images at a time. Is this MapServer, ecw, or a server problem? Here is
> the site:

Rene,

What exactly do you mean when you say it craps out?  Do things work fine
when you have 1-3 users rendering high resolution (from ECW) views, but
"crap outs" start happening with 4 or more?   Does your Chameleon based
application run as a cgi or "within the web server" as a loadable module?
Can you reproduce this issue by running overlapping shp2img'es on the
ECW data?

My guesses are:
  o You are using PHP as a loadable module and some sort of thread interference
    problem is occuring (unlikely since I don't think PHP MapScript is in wide
    use as a loadable module).
  o Some sort of file locking issue with the ecw files - unlikely, but would
    be reproducable with shp2img.
  o Reading ECW files is pretty resources intensive, and having several ECW
    renders going on at the same time is exausting system resources.  A system
    resources monitor on the server should give some idea about this.

I strongly encourage you to try and reproduce the problem with shp2img, and to
look for any sort of error messages, tracebacks or something that would help
isolate the problem.

Good luck,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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