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From Dirk-Willem van Gulik <>
Subject Re: [users@httpd] Timing Apache Responses
Date Mon, 22 Nov 2004 22:40:49 GMT

On Thu, 18 Nov 2004, Chris Hemsley wrote:

> I am supporting an internet based application which uses Apache as the
> webserver. There is an SLA in place for the application but because we
> cannot guarantee the performance of the internet, we wanted to report
> the time taken for a request to be processed before it returns to the
> users.
> I had originally thought that using the %T option in LogFormat would
> provide this information but results of tests I have carried out and
> comments in this mailing list indicate that the response time reported
> by Apache includes sending the response back to the user.
> I need a way to time the Apache responses without including the
> network lag. I would be interested in hearing from anyone who has
> encountered a similar problem and what solutions they have devised.

Unfortunately what you want is virtually impossible from within apache.
Aside from the way it composes the result internally - your main enemy is
the TCP stack of your system which buffers no end. Especially when you
have non LAN web-surfers.

I've done this commercially by creating SLA specific monitoring software
which is inserted into the IP stack of the web sever host or which ran on
a machine in front of the web server farm - much like a load balancer.


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