12. Connecting Apache and Tomcat using mod_jk2

Since (for some odd reason) some network managers allow outgoing web connections only to TCP port 80, there might be people around that cannot access your Tomcat (and MMBase) server through port 8080. You can install a JK 2 mapping or a reverse proxy in Apache, so Tomcat and MMBase can be accessed through the Apache web server at port 80. Apart from the port issue, this has the advantage that you can use Apache to manage you SSL connections and use your existing Apache logs and statistics facilities for Tomcat and MMBase as well.

Here we describe the installation and configuration of the JK 2 Connector connecting Apache and Tomcat. In this way, Tomcat paths can be mapped into Apache.

>From the JK 2 Connector website (http://jakarta.apache.org/tomcat/tomcat-4.1-doc/config/jk2.html):

" The JK 2 Connector element represents a Connector component that communicates with a web connector via the AJP protocol. This is used for cases where you wish to invisibly integrate Tomcat 4 into an existing (or new) Apache installation, and you want Apache to handle the static content contained in the web application, and/or utilize Apache's SSL processing. In many application environments, this will result in better overall performance than running your applications under Tomcat stand-alone using the HTTP/1.1 Connector. However, the only way to know for sure whether it will provide better performance for your application is to try it both ways. "

If you will only be needing a simple configuration-- typically a single Tomcat server sitting on the same system as your Apache server-- Apache reverse proxies might be an easier solution for you. Although these are simpler in terms of the interconnection features, reverse proxies provide more flexibility in fiddling with your paths and other options. The configuration of Apache reverse proxies is described in the next section.

However, if you plan to build or grow to a farm of several Tomcat servers behind an Apache front-end or build a high-performance system, deploying the JK 2 Connector is the way to go.

Download the sources of the JK 2 Connector from the Apache Jakarta website:

http://jakarta.apache.org/site/sourceindex.cgi

Extract and compile the JK 2 Connector:

tar -zxvf jakarta-tomcat-connectors-jk2-src-xxx.tar.gz cd jakarta-tomcat-connectors-jk2-src/jk/native2/ ./configure \ --with-apxs2=/usr/local/apache/bin/apxs make

Make sure your $JAVA_HOME environment variable is set and the Java binaries are in your $PATH or add this option to your ./configure command:

--with-java-home=/usr/local/j2sdk

Copy the module files mod_jk2.so and jkjni.so to the modules/ directory of Apache:

cp -i ../build/jk2/apache2/*.so /usr/local/apache/modules/ chmod 755 /usr/local/apache/modules/mod_jk2.so chown root:root /usr/local/apache/modules/mod_jk2.so chmod 755 /usr/local/apache/modules/jkjni.so chown root:root /usr/local/apache/modules/jkjni.so libtool --finish /usr/local/apache/modules

Copy the sample configuration file workers2.properties to the configuration directory of Apache:

cp -i ../../jk/conf/workers2.properties /usr/local/apache/conf/ chown root:root /usr/local/apache/conf/workers2.properties chmod 644 /usr/local/apache/conf/workers2.properties

and adjust it to your own needs.

Here is a simple configuration that should get you up and running:

[logger] # outcomment this in production use level=DEBUG [config:] file=${serverRoot}/conf/workers2.properties debug=0 debugEnv=0 [uriMap:] info=Maps the requests. Options: debug debug=1 [shm:] info=Scoreboard. Required for reconfiguration and status with multiprocess servers file=${serverRoot}/logs/jk2.shm size=1000000 debug=0 disabled=0 [workerEnv:] info=Global server options timing=1 debug=0 [status:] info=Status worker, displays runtime informations [uri:<hostname>/jkstatus/*] info=Display status information and checks the config file for changes. group=status: [channel.socket:localhost:8009] info=Ajp13 forwarding over socket # Define the worker [ajp13:localhost:8009] channel=channel.socket:localhost:8009 [uri:<hostname>/mmbase-webapp/*] info=MMBase

Most of this configuration is pretty standard. The last uri declaration (replace <hostname> with your hostname) is what this is all about; it maps all client requests starting with /mmbase-webapp/ from Apache to your Tomcat server.

So now, the same application you accessed through Tomcat as (replace <hostname> with your hostname):

http://<hostname>:8080/mmbase-webapp/

will be available through Apache as:

http://<hostname>/mmbase-webapp/

If your Apache installation is serving only a single website, you can leave out the hostname:

[uri:/mmbase-webapp/*] info=MMBase

which will serve the mapped /mmbase-webapp/ directory on every address and site of your Apache installation.

After adding the mod_jk2 module to your Apache configuration (in the file /etc/httpd/conf/httpd.conf or in a new file jk2.conf in the Apache configuration directory /etc/httpd/conf.d):

# Load mod_jk2 module LoadModule jk2_module modules/mod_jk2.so

chown root:root /etc/httpd/conf.d/jk2.conf chmod 644 /etc/httpd/conf.d/jk2.conf

you can now restart Apache and give your new entrance a try: (replace <hostname> with your hostname):

http://<hostname>/mmbase-webapp/

To check the status of the JK 2 Connector (replace <hostname> with your hostname):

http://<hostname>/jkstatus/

In case of any problems, check the JK 2 Connector log messages that will be written to your Apache error_log.

Access requests mapping to Tomcat will be logged in the access_log's and error_log's of Apache.

For more information on the workers2.properties configuration, check the documentation at:

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/jk2/jk2/configwebcom.html

There you will read about setting up more (remote) Tomcat workers, grouping these together in load-balancing pools, setting up RPC channels, using Unix sockets, using the Java Native Interface (JNI) to interconnect with Tomcat directly (in-process), setting up alternative loggers, and optimizing your time-outs.

You can find more general information about the JK 2 Connector at:

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/jk2/