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

[Alan Sparks]

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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