On 1/21/2011 12:32 PM, Dave Steinberg wrote:
Hi folks, first, this may be a tricky problem since it seems entirely
inconsistent. Good times!
I've noticed since switching to peruser that some requests seem to
randomly return with what my load balancer (Pound) translates into a 500
error code of "Internal server error". Upon deeper investigation, Pound
is not the problem, since I ran Apache jmeter directly against my web
backend and produced similar results.
I have a very simple script that intentionally takes a long time (~20
seconds) to complete its work. The script is:
====
#! /usr/bin/perl
$| = 1;
print "Content-type: text/html\n\n";
print "<html><head><title>trickling write test</title></head><body>\n";
for (my $i = 1; $i < 20; $i++) {
print "--> $i <br>" ;
sleep 1;
}
print "</body></html>";
exit 0;
====
If I run jmeter against that URL for a few hundred iterations, I get
anywhere from 10-30% error rates. The error I'm getting isn't a HTTP
error, but rather, a premature EOF (i.e. no HTTP response is sent).
I cranked my LogLevel to debug, but so far I haven't seen anything in
the logs that is interesting. Likewise, server-status shows 100%
availability for all workers.
My peruser config is:
IdleTimeout 600
ExpireTimeout 1800
MinSpareProcessors 5
MaxSpareProcessors 15
StartProcessors 5
MinProcessors 0
#MaxProcessors 100
MaxProcessors 400
ServerLimit 3000
MaxClients 1500
MaxRequestsPerChild 1000
#MinMultiplexers 100
MinMultiplexers 15
MaxMultiplexers 200
MultiplexerIdleTimeout 600
ProcessorWaitTimeout 10
MaxCPUUsage 50
# works, but prevents cores
#MultiplexerChroot /var/empty
# define a default processor
<Processor global_default>
User www
Group www
</Processor>
ServerEnvironment global_default
Any suggestions welcome, including debugging tips. :/
Just following up quickly - I did some more poking with the test script.
I get approximately a 2% error rate when the loop variable is dropped
to '2', i.e. 2 seconds per request, minimum. At 0 or 1, I can't detect
any errors in 1000 iterations.
Do other people see similar results in their peruser setups?
PS: 'ab -n 20 -c 1000' ought to produce equivalent results to what I'm
seeing in jmeter.
--
Dave Steinberg
http://www.geekisp.com/
http://www.steinbergcomputing.com/
http://www.redterror.net/
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