Purposeful Procrastination » Blog Archive » apache2, tomcat and mod

apache2, tomcat and mod_proxy

Making Tomcat work with a web server is a lot easier than it used to be, but that isn’t saying a whole lot. There are quite a number of questions about this on the web, so hopefully my experience will be helpful to someone.

I needed to link Apache 2 to Tomcat 5.5 on a Debian box. There are two general methods used for this: mod_jk or mod_proxy. There are variations, but these are the usual suspects. Also in general, mod_jk is considered the faster option (though as a third alternative a standalone Tomcat instance will do the job quite well - if you don’t require anything but Java).

I tried to use JK by downloading and compiling it, however apxs2 isn’t installed and apt-get refused to install apache2-threaded-dev (apparently a broken package as some dependencies were out of whack). So mod_proxy was it.

I found these instructions (kindly translated by Babelfish), which gave me the general idea, and later the Tomcat docs themselves brought forth the Proxy HOW-TO, which is a useful, step-by-step guide.

Based on the steps in the above guides, I used the following configuration:

mod_proxy configured for reverse proxying:

    # reverse proxy
    ProxyRequests Off

    # allow proxying of all requests;
    # don't turn ProxyRequests On with this configuration!
    <Proxy *>
      Order deny,allow
      Allow from all
    </Proxy>

Rewrite rules in VirtualHost definition:
```
    #tomcat rewrite/proxy directives
    <IfModule mod_rewrite.c>
        RewriteEngine On
        RewriteLog "/var/log/apache2/rewrite.log"
        RewriteLogLevel 1
        RewriteRule ^/url-path/(.*) http://localhost:8081/context-path/$1 [P]
    </IfModule>
```
Note url-path is the path that will be redirected, context-path is the Tomcat context, and 8081 is assumed to be the port your proxied Tomcat HTTP connector is listening on.

Note also that the rewrite rule is such that a request for http://meh.com/foo would fail, but http://meh.com/foo/ would succeed. There is probably a way around this, using a slightly different regex, but I haven’t taken the time.

The Tomcat docs detail different directives; I’ve seen fragments on the web saying that these don’t rewrite headers properly, but I’ve yet to work out the details of this.
In Tomcat’s server.xml, the connector includes the proxy attributes: <Connector port="8081" proxyName="external-domain-name" proxyPort="80"  />

After reloading Apache and restarting Tomcat it all appears to work. I would like to work out how to get mod_jk working at some point though - and perhaps (if I have a weekend to spare) getting the latest Apache to work with its newer connector modules. Enabling SSL is another job that will happen somewhere along the line too.

An interesting side-note to this connection method is the possible impact on caching, as Nick found out. I don’t think this will affect me much at this point, but it’s worthwhile keeping it in mind.

This entry was posted on Monday, April 10th, 2006 at 12:30 am and is filed under Java. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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