[smokeping-users] Re: EchopingHTTP ignore_cache

Stephane Bortzmeyer bortzmeyer at nic.fr
Thu Jul 29 09:00:40 MEST 2004

On Wed, Jul 28, 2004 at 07:45:13PM +0100,
 j.wu1 at lancaster.ac.uk <j.wu1 at lancaster.ac.uk> wrote 
 a message of 13 lines which said:

> while I am doing the EchopingHTTP probe, I want my smokeping go
> straight to the orgin web server.

In that case, the best solution is to give the probe the name of the
origin Web server (host = www.example.com). Unless there is a
transparent proxy on the road.

> What I am worried about is that the echoping will hit a proxy cache
> and return me with the latency through that cache. I notice the
> probe has ignore_cache options. Does it ignore all the caches alone
> the way to the web server or it is doing something else?

It just sets the "Cache-control: no-cache" header. RFC 2616 says:

       Cache-Control: no-cache

   to force any intermediate caches to obtain a new copy from the origin

So, if all the intermediate caches properly implement the RFC, it
should work. But you still have *some* processing in the proxy/cache
so, I repeat, the best solution is to direct the EchopingHTTP probe to
the original Web server (and to complain to your ISP if they have a
transparent proxy).

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