Re: acls and httpclose

From: Angelo Höngens <a.hongens#netmatch.nl>
Date: Fri, 23 Apr 2010 13:14:29 +0200

On 21-4-2010 23:54, Willy Tarreau wrote:

>>> I want to use haproxy for content switching on a large scale (lot of
>>> acls, lot of backends), but with httpclose on haproxy uses 25% cpu,
>>> without httpclose haproxy uses 5% cpu. So I'd rather not use httpclose
>>> if I don't have to..
>>
>> Also looks ok, since if you use httpclose haproxy got more work, so
>> cpu also got more work.

>
> In fact it's not much more work for haproxy, but for the system, doing
> a connect is more expensive than a send of one packet. However, if you
> observe that large differences, I conclude that you're transfering very
> small objects so that the connect/close overhead becomes predominant.
>
> My observations are that http-server-close is about twice as fast as
> httpclose, so you could save about half of the CPU usage here.
>
> Willy
>

Trying to wrap my head around this.. I read the configuration guide, and let me see if I understand correctly: when I use the http-server-close option, connections between haproxy and the backends or not persistent, but for each request, a new connection will be established.

But this adds the overhead of connection establishment, and should increase cpu usage, not descrease it, right? What am I missing? (Keep in mind I'm only talking about the haproxy machine, don't care about the backend server.)

The http-close option does about the same thing, but it is about connection between the clients and haproxy.

To me the backend-side and the client-side are two seperate things, which have little to do with eachother. Still, you say "http-server-close is about twice as fast as httpclose". Am I not interpreting things right?

-- 


With kind regards,


Angelo Höngens
systems administrator

MCSE on Windows 2003
MCSE on Windows 2000
MS Small Business Specialist
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Received on 2010/04/23 13:14