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From Plüm, Rüdiger, VF-Group <ruediger.pl...@vodafone.com>
Subject Re: ping for http in mod_proxy
Date Wed, 13 Feb 2008 18:09:58 GMT
 

> -----Ursprüngliche Nachricht-----
> Von: Jim Jagielski 
> Gesendet: Mittwoch, 13. Februar 2008 19:00
> An: dev@httpd.apache.org
> Betreff: Re: ping for http in mod_proxy
> 
> 
> On Feb 13, 2008, at 12:41 PM, Plüm, Rüdiger, VF-Group wrote:
> >
> > Agreed, but I doubt that it is possible with a reasonable amout of  
> > health
> > check frequency to find out before the first real request falls  
> > through,
> > provided that your health checks are designed to only fail if the  
> > backend
> > is down. If your health checks are smarter and notice that the  
> > backend will
> > fail soon (e.g. because it reached 98% or 99% percent of its  
> > capacity) then
> > this is a different story and can be very useful.
> > Regarding the reactivation of a failed backend I fully 
> agree: Active  
> > health
> > checks would be an asset here instead of just retrying failed  
> > backends periodically
> > with real requests.
> >
> 
> Ideally, it would be nice if we had better insight on the
> actual health of the backends than a simple "do they respond
> to OPTIONS * and how long does it take", but that's pretty
> much all we can do unless go full-on multicasting of info
> ala mod_backhand... At least the balancer is setup to allow
> for load balancing based on that, if the submodule/provider
> actually existed :)

Right. Furthermore I guess we could create a generic module that needs a
URL configured for a HEAD request that only replies 200 if the backend can
still handle more requests. If it does not respond or with a different code
this backend would be dead. I guess this module needs to fork a separate
process / thread to do this checking periodically and modify the worker status
accordingly.
So much interesting work and so few time :-(.

Regards

Rüdiger


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