[mapserver-users] RE: CGI returning a 502 error

[Lime, Steve D (DNR)]

Yes, there is a preset limit on the number of parameters the MapServer cgi will accept and indeed it is 100. There are two ways to work around this.

1) Edit the MS_MAX_CGI_PARAMS setting in cgiutil.h and recompile.
2) Consider combining the requested layers calls into a single variable. That is:

Change 
  ...layer=layer1&layer=layer2&layer=layer3... 
to:
  ...layers=layer1+layer2+layer3...

You should see an error message from MapServer in your web server error log if you ran into this limitation...

Steve

-----Original Message-----
From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of stoli
Sent: Tuesday, September 21, 2010 11:19 AM
To: mapserver-users at lists.osgeo.org
Subject: [mapserver-users] RE: CGI returning a 502 error


I do not think it is a string length limit. The IIS returns a separate error
for that. At least it does when you exceed the URL length limit in a GET
request. 

I have been doing some tests and it looks like it might be more of a limit
in the number of parameters in the POST request. I can't find any info
regarding the maximum number of parameters that you can send in one request
(to an IIS server), but again, I would think that IIS would be responding
with a more specific error if the limit was with it. 

Is it possible that the MapServer CGI is limited to 100 POST parameters? 

Fawcett, David (MPCA) wrote:
> 
> According to the docs, starting with MapServer 5.0, there is no limit to
> the number of layers in a mapfile. 
> http://mapserver.org/introduction.html#layer-object
> 
> I am guessing that you are running into a different issue.  
> 
> Have you captured the post request string and examined it to make sure
> that it is valid?  
> 
> Are you running into a string length limit for your post request?  The URL
> for your post request would be limited to ~2k char for IE, but this only
> includes the URL to the server, not the key:value pairs.  There could be a
> size limit for post requests set on your Web server to help prevent DOS
> attacks.  I don't know where this would be set in IIS.
> 
> David.
> 
> -----Original Message-----
> From: mapserver-users-bounces at lists.osgeo.org
> [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of stoli
> Sent: Monday, September 20, 2010 6:18 PM
> To: mapserver-users at lists.osgeo.org
> Subject: [mapserver-users] CGI returning a 502 error
> 
> 
> I'm using the ms4w binaries (5.6.3) under IIS 7.
> 
> My application sends (via http POST) a lot of parameters to modify the
> .map
> file. Mostly to add features to layers that are turned off by default and
> then make them visible. When my parameters cause the map to show over 50
> layers, the IIS returns a 502 error. 
> 
> I realize that the max layers are set to 100 in the default map.h file,
> but
> like I said, I am using the compiled binaries from ms4w. Does anyone know
> if
> they change that to 50 when they compile, or should I look elsewhere to
> find
> my problem? 
> 
> 
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