[hobbit] Debugging help: bbtest-net gets http test timing wrong

Tim McCloskey devzero at cox.net
Mon Jun 16 06:40:56 CEST 2008

What do you have for
in the apache 2.0 boxes?

Alan Sparks wrote:
> Continuing to try to debug this problem, have tried about everything I 
> can to resolve the issues with http probes.  Including:
> * Complete rebuild of the server with CentOS 4.6 and recompile of 
> Hobbit.  Same issues.
> * Removing everything from /etc/sysctl.conf, rebooting.  Same issues.
> * Manipulating the httpd.conf configs on remote servers, forcing 
> HTTP/1.0, removing ETags, creating a very simple index page to test 
> against.  Same issues.
> * Upgrading Apache on sample remote server to Apache 2.2.8 (most are 
> 2.2.4).  Same issue.
> * Recompiling Hobbit with debugging flags, to make sure the optimizer is 
> not applied.  Same issue.
> The only two servers I have that seem to work consistently well are a 
> pair of Apache 2.0.52 servers.  The 2.2.4+ servers all seem to give 
> Hobbit issues.  Although, again, repeated curl or wget probe cycles 
> against the servers from the Hobbit server never show more than a 0.2s 
> response time.
> But, Hobbit continues to report things like:
> - OK
> HTTP/1.1 200 OK
> Date: Mon, 16 Jun 2008 00:54:03 GMT
> Server: Apache/2.2.8 (EL)
> Last-Modified: Sun, 15 Jun 2008 00:37:00 GMT
> ETag: "7c809f-9b-44fa9b5806300"
> Accept-Ranges: bytes
> Content-Length: 155
> Connection: close
> Content-Type: text/html; charset=UTF-8
> I can't come up with anything other than Hobbit as a cause. But is there 
> anything I can do to trace what is happening internally to get past this 
> problem?  Any ideas at all would really be appreciated.  Thanks in advance.
> -Alan
> Seconds:     3.00
> Alan Sparks wrote:
>> Have a new install of Hobbit (4.2, tried 4.3 snap as well) on a fresh 
>> install of CentOS 4.6 x86_64, up to date on patches.  I have a problem 
>> with HTTP tests on "random" web servers that I just can't figure out.
>> I have about 64 of my hosts in the bb-hosts on this server, and have 
>> http tests defined for these servers.  On most of these servers, 
>> Hobbit is reporting the "Seconds:" for the response at 3 seconds.  It 
>> seems that it is inconsistent -- one cycle to the next, the 3-second 
>> response may move to a different set of servers.
>> The http: tests are defined using the IP address of the server - no 
>> server name (so no DNS lookup).
>> I've run a loop of tests on the same URL using wget and with curl, and 
>> used my browser and Telnet to connect to the same URL.  I consistently 
>> get a response time of about 0.2 seconds maximum from the servers.
>> The bbnet entry in hobbitlaunch.cfg looks like:
>> CMD bbtest-net --report --ping --checkresponse --debug
>> With the debugging turned on, I see the following entries periodically 
>> in the network test log:
>> Address=, open=1, res=0, err=0, connecttime=0.002965, 
>> totaltime=3.006810,
>> Address=, open=1, res=0, err=0, connecttime=0.002956, 
>> totaltime=3.007413,
>> Address=, open=1, res=0, err=0, connecttime=0.002860, 
>> totaltime=3.007120,
>> The problem does not affect the same hosts each time.  The problem 
>> will show a different number of hosts usually each cycle, sometimes on 
>> same servers, but often on different ones.
>> I've tried the following to see if anything will help:
>> * Reducing the number of hosts.  If I only have a couple or three in 
>> the bb-hosts, the problem doesn't manifest.
>> * Recompiling.  Doesn't help.
>> * Changing the test URL.  Doesn't help.
>> * Adding a --concurrency= option to the launch.  If I use a 
>> concurrency of 1, the problem does not manifest.
>> Setting the concurrency to 1 to fix the problem isn't an option, but 
>> makes me think something is getting really mixed up in the select() 
>> processing in bbnet.
>> Does anyone have any ideas how to diagnose where Hobbit is coming up 
>> with a 3-second latency, when none of my test tools running off the 
>> same server can duplicate the same timing?
>> Thanks for any ideas, this is really baffling me.
>> -Alan
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