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

[shane skoglund]

Did you rebuild the hobbit binaries on a 64 bit machine?  Or did you install
the all the 32 bit compat libs?


On Tue, Jun 17, 2008 at 6:00 PM, Alan Sparks <asparks at doublesparks.net>
wrote:

> 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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>>
>>
>
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