[mapguide-users] Server Error, unable to connect to fastcgi server. [No Viruses detected]

[Trevor Wekel]

Hi Chris, Hi Tom,

MapAgent.exe and php-cgi.exe are both CGI and FastCGI applications.
They can be configured to function as standalone CGI apps or as longer
lifetime FastCGI apps.  As part of the performance optimization for
MapGuide we chose to use FastCGI.

When configured as regular CGI apps, process loading and initialization
becomes a significant part of the execution time.  For PHP, the entire
API definition of approximately 130 classes and 1400 methods has to be
registered with the PHP runtime.  This is lot of memory allocation and
initialization.  The Mapagent loads/initializes faster but it still
takes time.  Incurring 200+ milliseconds of overhead for a 10
millisecond HTTP request was very performance restrictive.

Mapagent.exe and php-cgi.exe also connect to MapGuide Server through
TCP/IP.  When run as regular CGI's, these processes can exhaust the
ephemeral ports on both Windows and Linux.  From what I remember, the
default port pool on Windows is around 3000 ports and they stay in a
TIME_WAIT state for 4 minutes after they are closed.  A request rate of
around 12 requests per second for 4 minutes is sufficient to completely
exhaust the ephemeral ports on the server.  Once this happens, no new
TCP/IP connections will be accepted for any process running on the
machine.  Under some of our internal load tests, I could force this
condition in about 30 seconds.  When run as FastCGI apps, the Mapagent
and php-cgi reuse existing connections to the server which completely
avoids this problem. 

Isapi_fcgi.dll is an IIS extension for handling FastCGI applications.
With the default setups, both Mapagent.exe and php-cgi.exe run under
this IIS extension.  The Mapagent.fcgi file is just a placeholder.  It
makes it easier to configure either a FastCGI or regular CGI Mapagent
without having to change any URLs.  For FastCGI, Mapagent.fcgi redirects
to isapi_fcgi.dll which then calls a running mapagent.exe process.  For
regular cgi mapagent.fcgi just redirects to mapagent.exe.


It is possible to configure the Mapagent and php-cgi.exe as regular CGI
apps.  Initially, MapGuide was configured that way.  But there will be a
performance hit and the default settings for TCP/IP may need to be
adjusted to avoid ephemeral port exhaustion.


Thanks (for reading all this),

Trevor
 

-----Original Message-----
From: Chris Gountanis [mailto:cgountanis at mpower-tech.com] 
Sent: Tuesday, November 14, 2006 10:50 AM
To: users at mapguide.osgeo.org
Subject: RE: [mapguide-users] Server Error, unable to connect to fastcgi
server. [No Viruses detected]

With that being said is there a better way to setup the IIS/PHP config
in IIS. I was told be a few people that they had to change the PHP and
FCGI handlers manually after the fact. Why are PHP pages handled with
the isapi_fcgi.dll file and not the php-cgi.exe file? What is the big
diff from using mapagent.fcgi or using MapAgent.exe directly. What is
the fcgi file actually redirecting to?


--
Chris

-----Original Message-----
From: Tom Chadwin [mailto:tom.chadwin at nnpa.org.uk]
Sent: Tuesday, November 14, 2006 11:37 AM
To: users at mapguide.osgeo.org
Subject: [mapguide-users] Server Error, unable to connect to fastcgi
server.
[No Viruses detected]

Hello all

I get the following error message intermittently in my W2K3/IIS/PHP
application:

Server Error, unable to connect to fastcgi server.

A refresh often gets rid of the problem. I can't find anything in the
Windows event logs. Can anyone point me towards finding the cause of
this problem?

Thanks

Tom



Tom Chadwin
ICT & Web Development Officer
Telephone: 01434 611530
Mobile: 
Fax: 01434 611677
Email: tom.chadwin at nnpa.org.uk
Web : www.Northumberland-national-park.org.uk
<http://www.Northumberland-national-park.org.uk>

<http://www.northumberland-national-park.org.uk/> 
 
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