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

[Alan Sparks]

After some Googling, I have added "AcceptFilter http none" directives to 
the Apache 2.2 servers, which hasn't really helped anything...

Perhaps I should ask:  Can anyone verify Hobbit works correctly on a 
64-bit system?  Not should, but does, on a Centos 4 or RHEL 4 x86_64 
install?

I see a lot of debugging trace stuff (dbgprint calls) in the contest and 
httptest code.  Can anyone tell me how to enable it to trace what Hobbit 
is doing?

Am really at a loss.  This can't be rocket science to get it to probe 
HTTP correctly.  But a week later, I still cannot get it to match any 
other monitoring tool's results.
-Alan

Alan Sparks wrote:
> tcpdumps show a couple of interesting points.
>
> 1) There are definitely no DNS lookups occurring as a consequence of 
> the Hobbit probes.  No port 53 traffic out.
>
> 2) The packets from the Hobbit server, and the incoming packets to the 
> Apache server, sometimes look like:
>
> 15:20:01.160095 IP (tos 0x0, ttl  62, id 31129, offset 0, flags [DF], 
> proto 6, length: 60) hobbit.45116 > target.http: S [tcp sum ok] 
> 265769416:265769416(0) win 17520 <mss 8760,sackOK,timestamp 143665233 
> 0,nop,wscale 2>
>
> 15:20:04.159715 IP (tos 0x0, ttl  62, id 31131, offset 0, flags [DF], 
> proto 6, length: 60) hobbit.45116 > target.http: S [tcp sum ok] 
> 265769416:265769416(0) win 17520 <mss 8760,sackOK,timestamp 143668233 
> 0,nop,wscale 2>
>
> 15:20:04.160223 IP (tos 0x0, ttl  62, id 31133, offset 0, flags [DF], 
> proto 6, length: 40) hobbit.45116 > target.http: . [tcp sum ok] 
> 265769417:265769417(0) ack 1051782089 win 17520
>
> So that accounts for three seconds... it appears there are 2 SYN 
> packets, but the first isn't getting processed and there's a 3-second 
> delay to the next SYN (which gets ACKed).  I don't know why this 
> happens only with the Hobbit connections... and I don't know why the 
> first SYN seems to be getting ignored.  Server is not at all busy.
>
> -Alan
> Tim McCloskey wrote:
>> I get that wget/curl always work.  Not sure what resolver settings 
>> may be implemented differently for hobbit.
>>
>> Still thinking this may be unrelated to hobbit (even though wget/curl 
>> work fine for you).  We have many apache boxes spanning multiple 
>> networks running httpd versions 1.3, 2.0 and 2.2 that hobbit(4.2 with 
>> allinone patch) likes just fine and reports accurate times (Seconds: 
>> 0.nn).  We also have fairly proper forward and reverse DNS records 
>> for the systems involved.
>>
>> I can't imagine hobbit parsing the wrong response times, but if that 
>> is the case I wonder what external libraries are used (not hobbit 
>> provided libs, as ours parse fine and are likely the same as yours).
>>
>> Anyway, good luck with the tcpdump.
>>
>> Regards,
>>
>> Tim
>>
>>
>>
>>
>>
>> Alan Sparks wrote:
>>> UseCanonicalName is off, and HostNameLookup is off, on every server, 
>>> regardless of version.
>>> -Alan
>>>
>>> Tim McCloskey wrote:
>>>> What do you have for
>>>> UseCanonicalName
>>>> in the apache 2.0 boxes?
>>>>
>>
>>
>>
>>
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>>
>>
>>
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