[Xitami] 50+ simultaneous users...

[Thomas J. Hruska]

Today I have been stress testing Xitami under a very controlled environment
with a distributed attack server (DAS) and client (DAC) set.  The DAS and
DAC are multi-threaded applications capable of handling virtually any load
handed to them.  The problem I'm having seems to lie in Xitami when I
exceed 50 simulated simultaneous users (e.g. 50 users constantly hitting
reload).  Here is a sample of the log files for about 10 simultaneous users:

10.5.225.202 - - [13/Mar/2002:00:04:01 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 8
10.5.225.202 - - [13/Mar/2002:00:04:01 -0500] "GET /distattack/dist2.cfm
HTTP/1.1" 200 1119
10.5.225.202 - - [13/Mar/2002:00:04:01 -0500] "GET /distattack/dist2.cfm
HTTP/1.1" 200 1119
10.5.225.202 - - [13/Mar/2002:00:04:03 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 8
10.5.225.202 - - [13/Mar/2002:00:04:03 -0500] "GET /distattack/dist1.cfm
HTTP/1.1" 200 99342
10.5.225.202 - - [13/Mar/2002:00:04:04 -0500] "GET /distattack/dist2.cfm
HTTP/1.1" 200 1119
10.5.225.202 - - [13/Mar/2002:00:04:05 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 8
10.5.225.202 - - [13/Mar/2002:00:04:05 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 8
10.5.225.202 - - [13/Mar/2002:00:04:05 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 8
10.5.225.202 - - [13/Mar/2002:00:04:09 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 8
10.5.225.202 - - [13/Mar/2002:00:04:09 -0500] "GET /distattack/dist1.cfm
HTTP/1.1" 200 99342
10.5.225.202 - - [13/Mar/2002:00:04:11 -0500] "GET /distattack/dist1.cfm
HTTP/1.1" 200 99342

These are the correct file sizes for this.  Now, when I attempt to simulate
50 simultaneous users, the log file looks like this:

10.5.225.202 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist1.cfm
HTTP/1.1" 200 2
10.5.228.37 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 2
10.5.225.202 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 2
10.5.228.37 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist2.cfm
HTTP/1.1" 200 0
10.5.225.202 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist1.cfm
HTTP/1.1" 200 0
10.5.228.37 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist1.cfm
HTTP/1.1" 200 2
10.5.228.37 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 2
10.5.228.37 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist2.cfm
HTTP/1.1" 200 2
10.5.228.37 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist3.cfm
HTTP/1.1" 200 2
10.5.228.37 - - [13/Mar/2002:20:49:30 -0500] "GET /distattack/dist2.cfm
HTTP/1.1" 200 0


Xitami is returning with a fairly inconsistent zero or two bytes.  Only
once in a while is the correct webpage returned.  Note that 50 simultaneous
users is putting a steady 75-100% CPU load on my processors (the DAS has
only occupied 3 seconds of CPU time in the past 24 hours and the DAC only
consumes about 5 minutes of CPU time every 24 hours).  Xitami has consumed
1 hour of CPU time in the past 24 hours.

Note that XiFusion is not the problem since if I run another scripting
language not tied to XiFusion, I get the same sort of thing in the logs:

192.195.234.26 - - [13/Mar/2002:20:29:27 -0500] "GET /distattack/dist1.pl
HTTP/1.0" 200 0
192.195.234.26 - - [13/Mar/2002:20:29:59 -0500] "GET /distattack/dist2.pl
HTTP/1.0" 200 0
192.195.234.26 - - [13/Mar/2002:20:30:26 -0500] "GET /distattack/dist2.nvm
HTTP/1.0" 200 0
192.195.234.26 - - [13/Mar/2002:20:30:07 -0500] "GET /distattack/dist2.pl
HTTP/1.0" 200 0

My best guess is that Xitami is either killing processes (although I have
disabled that feature due to long-running web-based scripts I've written)
or it has hit an OS limit (total number of CGI processes allowed by a
single process).  Is this a known bug or what exactly is going on?  Any
suggestions?

My objective is to stress test up to 100 simultaneous users over a period
of 24 hours for each scripting language...but it looks like I might have to
trim back that objective unless there is another, more viable option.


          Thomas J. Hruska -- shinelight@shininglightpro.com
Shining Light Productions -- "Meeting the needs of fellow programmers"
                  http://www.shininglightpro.com/