[mapserver-dev] Mapserver issues with POST requests

Michel.Dastous at bentley.com Michel.Dastous at bentley.com
Mon Aug 4 10:51:07 PDT 2014


Over the past few months we have been experiencing stability issue with our MapServer 6.4.1 windows builds running under IIS 7.5 (configured as FastCGI module).

We discovered that IIS was restarting mapserv.exe instance after each request containing a POST body.    After investigation, I have found  that other projects using libfcgi were suffering from the exact same behavior.  The problem is well documented on http://forums.iis.net/t/1150498.aspx?FastCGI+Error+Number+233+for+Ruby+on+Rails+Configuration and http://www.perlmonks.org/?node_id=862506.

As suggested in the forum threads, I have applied the libfcgi patch available at: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=catagits/fcgi2.git;a=commitdiff;h=c4d74207308dfafa652925306c6b2828843e0e97

Once the patch applied,  Mapserv.exe was able to serve more than one request  before being recycled.  However, after performing stress tests with JMeter we were still getting an  error rate of ~10%.    So even with the libfcgi patch applied,  we keep having issues with POST requests.

The problem is difficult to reproduce, but at some point Mapserver.exe instances start hanging and the instance finally get killed by IIS.  I'm convinced that issue is caused by a bad libfcgi communication/behavior: each time the process hang, the application seems to be blocked on a FCGI_Accept call, which let us think the Mapserver's core code is not the root of the problem.

Looking at libfcgi website, I can see that version is 2.4.6 and have not been updated since 2007 and their mailing list seems to be dead, so it looks like it will be very difficult to get support from that project.

I'm interested in your thoughts and suggestion about this.


Michel D'Astous

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