Re: [Pound Mailing List] FreeBSD and failed requests

     I've made some progress on this.  It appears that when Pound is  
left in round-robin mode, and it is spraying around connections to  
multiple backends, that is when all the failed connections are  
generated.  I enabled IP based sessions and my failures went away  
immediately.  When causing the failures the only clue as to what is  
going on in the log is this:

May  5 14:52:58 fencer pound: backend 10.10.10.36:80 connect:  
Operation not permitted

     Then it resurrects, and fails again.  It almost as if the  
backend is being overwhelmed, but I don't think that is the case.  If  
you look over the ApacheBench numbers from previous emails you'll see  
that when going through Pound, the requests per second is much lower  
than when going to the web server directly.  For comparison purposes,  
I loaded lighttpd on the backend to see if it was Apache now being  
the source of the problem, but it topped out at the same requests per  
second.
     To strip this test to the bare minimum, there are now only  
three things involved:  My 12" PowerBook, and matching Sempron 2200+  
servers, both running FBSD 6.1-RC2.  So here is the latest runs of AB  
using this scenario:

12" PB -> Apache 2.2.2 server
Server Software:        Apache/2.2.2
Server Hostname:        10.10.10.36
Server Port:            80

Document Path:          /
Document Length:        17 bytes

Concurrency Level:      10
Time taken for tests:   1.137 seconds
Complete requests:      1000
Failed requests:        0
Broken pipe errors:     0
Total transferred:      265265 bytes
HTML transferred:       17017 bytes
Requests per second:    879.51 [#/sec] (mean)
Time per request:       11.37 [ms] (mean)
Time per request:       1.14 [ms] (mean, across all concurrent requests)
Transfer rate:          233.30 [Kbytes/sec] received

Connnection Times (ms)
              min   avg   max
Connect:        0     0    18
Processing:     1    10    43
Total:          1    11    43


12" PB -> Pound 2.0.4 server -> Apache 2.2.2 server
Server Software:        Apache/2.2.2
Server Hostname:        10.10.10.35
Server Port:            8080

Document Path:          /
Document Length:        17 bytes

Concurrency Level:      10
Time taken for tests:   2.693 seconds
Complete requests:      1000
Failed requests:        0
Broken pipe errors:     0
Total transferred:      265265 bytes
HTML transferred:       17017 bytes
Requests per second:    371.33 [#/sec] (mean)
Time per request:       26.93 [ms] (mean)
Time per request:       2.69 [ms] (mean, across all concurrent requests)
Transfer rate:          98.50 [Kbytes/sec] received

Connnection Times (ms)
              min   avg   max
Connect:        0     0    19
Processing:    13    26    49
Total:         13    26    49

     The things to note this time is that the failed connections are  
non-existent, since all requests are being directed at the same  
server each time.  The other thing which jumps out is the halved  
requests per second and increased testing time.  So while I've worked  
around one issue it's left me with another.  For the hell of it I  
rebuilt the kernels to use the ULE scheduler rather than the old 4BSD  
but the difference in performance was impossible to detect.
     One other point to make is that the Sempron machines can  
actually output more than the ~800 requests per second.  The 800 mark  
is a limit imposed by my PowerBook, throwing a 2.6Ghz HP at it drives  
that number to over 1700.


On May 5, 2006, at 9:47 AM, Robert Segall wrote:

> Something must show in the log files - at the very least the 50
> requests, together with their status. You may want to try LogLevel  
> 4 for
> a more verbose display.
>
> In any case I'd be curious to see what a "failed" request means: was
> there no response, or a wrong response, or perhaps a 5xx response?
>
> More info required...
> --
> Robert Segall
> Apsis GmbH
> Postfach, Uetikon am See, CH-8707
> Tel: +41-44-920 4904
>
>
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Network Administrator
IOWA Interactive
4212 Glencoe Ave
Marina Del Rey, CA 90292

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