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From Henri Gomez <>
Subject Re: Invitation to HTTPD commiters in tomcat-dev
Date Tue, 20 Jul 2004 14:22:33 GMT
Graham Leggett wrote:

> Henri Gomez wrote:
>> And what about using AJP/1.3 instead of HTTP for connection to tomcat ?)
> In all my deployments of tomcat I have never seen the point of a custom 
> protocol that did exactly what HTTP does, so all my tomcat deployments 
> are all HTTP, with a simple mod_proxy frontend.

Well AJP/1.3 save cycle in tomcat avoiding it to re-decode headers for 
examples. It forward also the SSL infos if needed. And AJP/1.3 use 
persistant connections so it safe cycle also.

jk was designed a long time ago so may be mod_proxy allready support
persistant connections.

> Even the "get Apache to server static content" feature wasn't enough of 
> a drawcard, as proper HTTP cache handling and a suitable cache solved 
> this problem. It was far more important for me to arrange the web 
> application as a self contained unit - I would rather be more tidy with 
> an install at the expense of a slightly higher load, than sacrifice a 
> clean install to save some cycles.
>> - If you add load-balancing/fault-tolerance and AJP 1.3 support in
>>   mod_proxy you'll have about 99% of the current functionalities of
>>   jk 1.2.x.
>> We discussed also the need for some dynamic mapping and topology 
>> discovery/update (between Apache and Tomcats Clusters).
> Proxy has a placeholder in it that says "put the code to make decision 
> about load balancing etc here" - all that is needed is a hook and a 
> module "proxy_loadbalancing.c" to make it happen.

Great. And if you handle in the proxy_loadbalancing.c
the JSESSION_ID, (sticky session) to map next requests
to the tomcat who set it, you'll have everything needed.

Of course you should also handle some mixed cases, like full
round-robin, and sticky round-robin.

The idea is interesting.

>> And in fine, we like to have some JMX like functionnalities in Apache 2,
>> in our case CMX for C Management Extension, a way to update Apache 2.x
>> configuration while the server is running...
> This is possibly a whole separate project in itself.
> I have been meaning to work on a get-apache-config-out-of-ldap extension 
> for a while, what it really should be is "get apache config out of 
> wherever", but this should be an Apache wide thing, not limited to a 
> single module or technology.

Well LDAP could be use for configuration outside a file. JMX/CMX goes a
bit farther since it let you update some characteristics at runtime.

But I agree that providing a JMX/CMX facade to Apache 2.x modules will
be a good starting point. Costin will certainly clarify this point with

In fine the discussed mod_ajp module should detect topology change in a
second phase to learn for example that a tomcat in a cluster 
started/stopped a web application, so next requests could be redirected
to another tomcat in the cluster. Also you should be able to update the
load factor for each tomcat, may be having a load factor by Webapplication.

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