[gentoo-user] Re: TCP Queuing problem

[Grant <emailgrant@gmail.com>]

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>>> My web server's response time for http requests skyrockets every
>>> weekday between about 9am and 5pm.  I've gone over my munin graphs and
>>> the only one that really correlates well with the slowdown is "TCP
>>> Queuing".  It looks like I normally have about 400 packets per second
>>> graphed as "direct copy from queue" in munin throughout the day, but 2
>>> to 3.5 times that many are periodically graphed during work hours.  I
>>> don't see the same pattern at all from the graph of all traffic on my
>>> network interface which actually peaks over the weekend.  TCP Queuing
>>> doesn't rise above 400 packets per second all weekend.  This is
>>> consistent week after week.
>>>
>>> My two employees come into work during the hours in question, and they
>>> certainly make frequent requests of the web server while at work, but
>>> if their volume of requests were the cause of the problem then that
>>> would be reflected in the graph of web server requests but it is not.
>>> I do run a small MTU on the systems at work due to the config of the
>>> modem/router we have there.
>>>
>>> Is this a recognizable problem to anyone?
>>
>>
>> I'm in the midst of this.  Are there certain attacks I should check for?
>
>
> It looks like the TCP Queuing spike itself was due to imapproxy which
> I've now disabled.  I'll post more info as I gather it.


imapproxy was clearly affecting the TCP Queuing graph in munin but I
still ended up with a massive TCP Queuing spike today and
corresponding http response time issues long after I disabled
imapproxy.  Graph attached.  I'm puzzled.

- Grant

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