Spurious 500 errors

> Folks:
> 
> I'm getting spurious/intermittant HTTP-500 errors from a FastCGI app and
> need to somehow get more information from FastCGI other than what shows up
> in the apache log (which is not much).  I know it is not the application
> crashing or giving back illegal headers.  It is the communication between
> the FastCGI processes and the master FastCGI controller (or whatever).
> 
> My app has been up and deployed for several weeks and has handled a fair
> number of concurrent users.  But today starting around 5:30pm, it started
> handing out random 500 errors.  Oddly enough, apache was bounced at around
> 4:00pm, ruling OUT that my persistent processes were somehow stuck (memory
> leaks or whatever).
> 
> Out of 17,831 requests today, 44 resulted in 500 errors.  That may not
> seem like a lot, but that means 44 user-visible things broken in the
> browser (they entire page or an ajax component showing up with the 500
> error screen of death).
> 
> Although I can reproduce it fairly quickly, there is no telling which
> request will give back a 500 error (it is not consistent).  According to
> the apache log, the FastCGI exes are return NOTHING ("0 bytes"), which
> results in a 500, since even an empty web page needs a properly formed
> http header.
> 
> Here is an actual apache log extract showing 500 errors interspersed with
> normal requests.  Note that I send the apache access and error log output
> to the same file which helps this type of debugging:
> 
> [Tue Oct 16 22:06:14 2007] [error] [client 192.168.101.205] (32)Broken
> pipe: FastCGI: comm with server "/usr/local/packages/v1/linux/v.fcgi"
> aborted: write failed
> [Tue Oct 16 22:06:14 2007] [error] [client 192.168.101.205] FastCGI:
> incomplete headers (0 bytes) received from server
> "/usr/local/packages/v1/linux/v.fcgi"
> 192.168.101.205 - mhagerty [16/Oct/2007:22:06:10 -0400] "GET /tdc/v
> HTTP/1.1" 500 714
> [Tue Oct 16 22:08:11 2007] [error] [client 192.168.101.205] (32)Broken
> pipe: FastCGI: comm with server "/usr/local/packages/v1/linux/v.fcgi"
> aborted: write failed
> [Tue Oct 16 22:08:11 2007] [error] [client 192.168.101.205] FastCGI:
> incomplete headers (0 bytes) received from server
> "/usr/local/packages/v1/linux/v.fcgi"
> 192.168.101.205 - mhagerty [16/Oct/2007:22:08:07 -0400] "GET /tdc/v
> HTTP/1.1" 500 714
> aries.tpnyc.local - - [16/Oct/2007:22:08:24 -0400] "GET /tpt/v HTTP/1.1"
> 401 576
> aries.tpnyc.local - hnarin [16/Oct/2007:22:08:36 -0400] "GET /tpt/v
> HTTP/1.1" 200 20108
> aries.tpnyc.local - hnarin [16/Oct/2007:22:08:37 -0400] "GET
> /tpt/all-min.js HTTP/1.1" 304 -
> aries.tpnyc.local - hnarin [16/Oct/2007:22:08:37 -0400] "GET
> /tpt/skin-gl/ktab.css HTTP/1.1" 304 -
> aries.tpnyc.local - hnarin [16/Oct/2007:22:08:37 -0400] "GET
> /tpt/skin-gl/vencore.css HTTP/1.1" 304 -
> aries.tpnyc.local - hnarin [16/Oct/2007:22:08:37 -0400] "GET
> /tpt/skin-gl/vencore-ie.css HTTP/1.1" 304 -
> 192.168.101.205 - - [16/Oct/2007:22:08:36 -0400] "GET /tpt/v HTTP/1.1" 401
> 577
> [Tue Oct 16 22:08:53 2007] [error] [client 192.168.101.205] (32)Broken
> pipe: FastCGI: comm with server "/usr/local/packages/v1/linux/v.fcgi"
> aborted: write failed
> [Tue Oct 16 22:08:53 2007] [error] [client 192.168.101.205] FastCGI:
> incomplete headers (0 bytes) received from server
> "/usr/local/packages/v1/linux/v.fcgi"
> 192.168.101.205 - jkuefler [16/Oct/2007:22:08:49 -0400] "GET /tpt/v
> HTTP/1.1" 500 714
> 
> As far as tuning FastCGI, I am currently starting 30 processes with a
> queue depth of 100.  Here are all the relevant httpd.conf lines:
> 
> LoadModule fastcgi_module     modules/mod_fastcgi240_apache20.so
> AddHandler fastcgi-script     fcgi
> FastCgiServer /usr/local/packages/v1/linux/v.fcgi -processes 30
> -listen-queue-depth 200
> ScriptAlias /tpt/v     "/usr/local/packages/v1/linux/v.fcgi"
> ScriptAlias /tdc/v     "/usr/local/packages/v1/linux/v.fcgi"
> 
> I find it hard to believe that 30 processes is not enough, nor that the
> queue depth is too shallow.  The problem started occurring at off-peak
> hours (thankfully).  The machine is beefy: 2 GB RAM, 4 CPUs, etc.  Apache
> runs in a VM (Suse Linux) and the host operating system is XP.
> 
> Any insight and/or way to get MORE INFORMATION out of FastCGI is deeply
> appreciated.
> 
> Thanks,
>    jkuefler at translations dot com
> 
>

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