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Message-ID: <50ED8D03.8070804@christopherschultz.net>
Date: Wed, 09 Jan 2013 10:30:11 -0500
From: Christopher Schultz <chris@christopherschultz.net>
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To: Tomcat Users List <users@tomcat.apache.org>
Subject: Re: Communication flow with different connectors
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Vicky,

On 1/9/13 9:06 AM, vicki@thepenguin.org wrote:
> I appreciate your reply and apologize for the top post (am using a 
> stupid mail client from work).

You can't just press the /down/ arrow key a few times? *shrug*

> Your answer gets me part way there, but what is the most confusing
> to me is the use of JkMount. How does that fit into the picture
> from a communication perspective.

It's all configuration, not communication. Once configured, mod_jk and
mod_proxy_ajp work in exactly the same way (at least, the wire
protocol is the same -- the modules are obviously working somewhat
differently, internally).

Basically:

worker.foo.host=tomcat
worker.foo.port=8009
+
JkMount /myapp/* foo

is the same thing as this:

ProxyPass        /myapp/ ajp://tomcat:8009/myapp/
ProxyReversePass /myapp/ ajp://tomcat:8009/myapp/

mod_jk's older configuration uses a separate file to configure the
workers, then JkMount directives in httpd.conf in order to map URLs to
those workers. mod_proxy_ajp's configuration is done all in httpd.conf
and matches the configuration of all mod_proxy_* modules.

The configuration becomes more complex for both modules when using
load-balancing. mod_jk uses a single worker of type "lb" with other
workers actually connecting to Tomcat instances, then you use JkMount
as usual with the "lb" worker, so httpd.conf need not change at all to
introduce load-balancing. mod_proxy uses a <Proxy> directive to define
a balancer with various BalancerMember directives and then uses a
ProxyPass directive to map a URL space to that balancer, so httpd.conf
becomes more complicated when load-balancing is introduced.

Note that you can configure mod_jk entirely within httpd.conf if you
want, using JkWorkerProperty. I don't believe you can configure mod_jk
using such compact syntax as mod_proxy supports, yet mod_jk does
support "template" workers which can significantly simplify your
deployment if you have many workers to track.

Hope that helps,
- -chris
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