[mapserver-users] Mapserver crashes with large number of layers

[Jeff McKenna]

Hello,

I can give you the steps that I would do in this situation:

- test this on a different machine
- test on a 32bit machine
- test on a Linux machine
- if you build mapserv yourself, test with a binary/package (MS4W, FGS) 
and see if you can replicate the problem
- convert your layers to shapefiles and retest (in other words see if 
avoiding using OGR helps at all)
- get the exact CGI query string that causes problems in your browser 
and then try that same command through the commandline (examples at: 
http://www.mapserver.org/cgi/mapserv.html)...actually I would try that 
test first (because an error might be shown at the commandline, that is 
not displayed through the browser)
- test with one big mapfile (avoid using includes just to see if that is 
the issue)
- it might be an issue with tileindex on a layer...so if possible test 
without using a tileindex
- but really, the best test is to start reducing the number of layers 
until you find the minimum number of layers that still cause the 
problem..then focus your testing on those few layers that are causing 
troubles (I often do this, and yes it takes time)

Those are my initial thoughts.

-jeff



-- 
Jeff McKenna
MapServer Consulting and Training Services
http://www.gatewaygeomatics.com/





On 10-12-08 10:58 AM, Oliver Wesp wrote:
> Dear List,
>
> we're kind of stuck with the following problem:
>
> First of all we are running Mapserver 5.6.5 in CGI Mode on Windows
> 2003 Server (64bit). Webserver is Apache 2.2.
>
> We have a large Mapfile (seperated into 5 different parts using
> INCLUDE) with a total of 571 Layers. The layers have different
> MAXSCALEDENOM values  so not all of them are drawn at all scales. The
> layers are referencing the DATA via TILEINDEX (it's S-57 data read
> through OGR). Most of the layers cover only a small area, so if I zoom
> in to the map more and more layers must be taken into account of
> drawing but only a small number must be drawn. All of the layers are
> divided into three groups using the GROUP parameter.
> What happens if I zoom in to the map at some point mapserver crashes
> (actually it's not crashing it just stucks). If I reduce the total
> number of layers (by commenting out parts of the mapfile) the map will
> be drawn again. So my guess is that there is a problem with the number
> of layers (or styles?, or symbols?, or number of layers per group?)
> included.
> I turned on debugging on all of my layers but that didn't helped. If I
> check the taskmanager mapserver.exe goes to 100% cpu usage and goes
> back to zero after a few seconds but it's not being terminated. It's
> still running in the process list. Debug output stops right in the
> middle of the line. No error message is send to the client or written
> to any of the logfiles. Actually no response is send to the client at
> all. If I terminate the process using the task manager "Premature end
> of script headers: mapserv.exe" is written to the apache error.log and
> the client shows "Internal Server Error".
>
> Right know we have no idea of what to look at. If anybody has any hint
> what might goes wrong we maybe would be able to look at it and maybe
> fix it. But right now we're stuck.
>