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

[Oliver Wesp]

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.

Best regards,
Oliver