[MapServer-users] IIS - FastCGI - POST requests crashing mapserv

[Benedek Petrovicz]

Hi!

I have an environment where I run MapServer as a FastCGI application in IIS.
When a single mapserv instance (process) gets more than two concurrent POST
requests, the mapserv executable crashes.
IIS returns a default HTTP 500 error.
The exact error is: 233 - ERROR_PIPE_NOT_CONNECTED (No process is on the
other end of the pipe.)

Adding debugging to the map files didn't show me any valuable details.
Seems to be crashing while still trying to write into the debug logs.
There were half complete lines in there.

No logs in the Event Viewer.
No valuable logs in IIS.
I tried process monitoring, but I couldn't find anything useful there.

To reproduce it, in the FastCGI settings just limit the max number of
instances to 1 and flood it with a couple dozen concurrent requests.
You can use any tool. K6, Bombardier, PS script and .NET code each work for
that.
I attached a K6 script which I was using for it.

Required settings:

   - You need to send POST requests
   - The content type needs to be application/x-www-form-urlencoded (that's
   the only POST content type that works with MapServer as far as I know)
   - You don't even need a mapfile to reproduce the issue. You'll get the
   same result if you provide one.

If you set the max requests per instance down to 2, it won't crash.
Also, I couldn't crash it with GET requests.

Anyone have any idea about why this is happening?
Should I open a github issue for it?

Thanks
Benedek Petrovicz
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