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From Henri Gomez <>
Subject Re: jk/cluster - intelligent systems load
Date Mon, 15 Feb 2010 11:38:44 GMT
2010/2/12 Mark Thomas <>:
> On 12/02/2010 15:20, Henri Gomez wrote:
>> Hi to all,
>> Some times ago, we discuss about mod_jk/cluster and more intelligent
>> strategy to be use for the dispatching system.
>> One point was to get system load informations about the various Tomcat
>> instances involved in a cluster, to send request to the lowest loaded
>> Tomcat.
>> Hyperic Sigar,, seems to
>> provide such informations for various OS.
>> Could it be interesting to add such 'extension' to Tomcat, so it could
>> be able to send back to jk/cluster so they could get the best
>> decisions ?
>> New commands could be added to AJP13, as done previously with
>> cping/cpong,
>> What do you think about ?
> I like the general idea.


> My personal favourite in terms of implementation is to pass the
> information via response headers as it allows interoperability with the
> widest possible range of front-end load balancers. The info can be
> passed back with every request or only for requests to a particular URL.

Why not in response headers if it's discarded by the jk side.
These informations shouldn't be send back to the browser (security concerns).

> Then you get into how you measure load. I don't think that there will be
> a one size fits all solution. I imagine that it would need to be fairly
> easy for folks to implement their own load measurements. Using response
> headers makes that simple to do providing we get the definition of that
> header format right.

In response header it will allow both mod_jk (ajp), or mod_proxy
(http) to get such decision.

Question, how to add such informations in Tomcat ?
Extension ?

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