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From Filip Hanik - Dev Lists <>
Subject Re: ping for http in mod_proxy
Date Thu, 14 Feb 2008 10:20:34 GMT
Graham Leggett wrote:
> Jim Jagielski wrote:
>> 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 :)
> Is there anything stopping us going the multicasting route, say by 
> adding a hook or hooks of some kind to proxy that keeps track of known 
> server states?
> A dedicated module could then have it's job as handling the 
> multicasting and letting the rest of the server know if a server is on 
> or off the air, in realtime.
> The proxy can then just say "which of these servers should I connect 
> to?", and the hook will return the suggested ones in the given order.
> As a dedicated module, people who don't need it can turn it off or not 
> build it.
this is an idea I've been sitting on for a couple of years now.
Tomcat's cluster can also multicast more than just that the node is 
alive, it can broadcast, what applications (URL contexts) are available, 
how many threads are in use, what the server load is etc. It can even 
broadcast automount points, or when applications are being taken 
offline, while the server is still up.


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