Re: mod_perl server doesn't reply

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On Fri, 2005-03-18 at 17:37 -0500, Stas Bekman wrote:
> Anders, the first priority is to figure out how to reproduce the problem 
> at will. If you don't manage that, you most likely are going to waste 
> hours staring at the screen. I'd concentrate on that task first.
> 
> Try using ab (apachebench), httpd_load or another utility to stress test. 
> More advanced tools can record and reply real requests. For some examples see:
> http://modperlbook.org/html/ch09_01.html#pmodperl-CHP-9-SECT-1
> 
> Armed with one of these tools you can know exactly how many requests 
> you've issued and then making sure that logs/access_log is in agreement.
> 
> Also take a look at Apache::Resource which can set certain limits on the 
> process resource consumption.
> 

I have been doing some testing with ab and I found some interesting
cases.


On our production system I get the following when testing an important
mod_perl enabled script from my local desktop:

$ ab -n 100 -c 5 "http://www.xxxxxx.dk/cgi/xxxxxx.cgi?q=test&allowall=1";
This is ApacheBench, Version 2.0.40-dev <$Revision: 1.121.2.1 $>
apache-2.0
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd,
http://www.zeustech.net/
Copyright (c) 1998-2002 The Apache Software Foundation,
http://www.apache.org/

Benchmarking www.xxxxxx.dk (be patient).....done


Server Software:        Apache/1.3.33
Server Hostname:        www.xxxxxx.dk
Server Port:            80

Document Path:          /cgi/xxxxxx.cgi?q=test&allowall=1
Document Length:        44128 bytes

Concurrency Level:      5
Time taken for tests:   45.82097 seconds
Complete requests:      100
Failed requests:        21
   (Connect: 0, Length: 21, Exceptions: 0)
Write errors:           0
Total transferred:      4433142 bytes
HTML transferred:       4412842 bytes
Requests per second:    2.22 [#/sec] (mean)
Time per request:       2254.105 [ms] (mean)
Time per request:       450.821 [ms] (mean, across all concurrent
requests)
Transfer rate:          96.02 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        5  234 766.0     24    3016
Processing:   997 2002 1287.8   1330    6932
Waiting:       36  374 849.1     92    3082
Total:       1015 2237 1529.8   1393    7515

Percentage of the requests served within a certain time (ms)
  50%   1393
  66%   1756
  75%   3162
  80%   3670
  90%   4298
  95%   6101
  98%   6948
  99%   7515
 100%   7515 (longest request)


There are 21 failed requests which is surprising to me. The error type
is Length. What does this mean? I don't see any explanation of the
output of ab on the man page.



When testing our development server I sometimes get this error from ab:
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
apr_recv: Connection reset by peer (104)
Total of 3320 requests completed

I don't know what this mean either. I am not sure why the ab would die
of this kind of error instead of just reporting that an error happened.

Hope you can explain this.

Thanks
  Anders