1. Introduction
2. Overview
3. Files and Paths
4. JK Configuration
5. JK2 Configuration
6. Restart
7. Appendix A - Compilation Hints

1. Logging

   Apache can be configured to produce standard and custom logging reports. These can then be used to analyze and perhaps optimize the traffic to and from your web applications.

2. Speed

   Web applications typically consist of static files containing images, scripts, and documents and some dynamically generated content. These static files can then be served by a faster Web Server (such as Apache) which is specifically designed for this purpose rather than the Web Container, which is tuned for serving the dynamically generated content.

3. Security

   With the Web Server receiving the HTTP requests from the Internet, this becomes the first line of defence against attacks. As such there are usually many security features that the Web Server provides which will stop rogue attacks against the underlying infrastructure (Web Container.)

4. Integration

   By using a Web Server as a common front end it is easy to integrate multiple applications and web sites and redirectors behind it. This usually allows great flexibility in adding, changing and removing the content and services behind it.

Communication between Tomcat and Apache is handled by the JK connector, of which there is two versions, JK and JK2. Configuration for both versions is described here, however it should be noted that as of 15 November 2004, JK2 is no longer supported by Jakarta . Further information can be found on the Apache Jakarta Tomcat Connector website.

The connector can be downloaded from the jakarta-tomcat website. Binaries versions are available for many versions of Apache and operating systems, otherwise the source must be downloaded and compiled for your environment (see compilation hints for more details). The configuration in the following sections has been tested with JK 1.2.5 and JK2 2.0.2 (mod_jk.so and mod_jk2.so respectively) for Apache 2.0.40/Tomcat 4.1.30 and Apache 2.0.40/Tomcat 5.0.19.

Note: Due a change in the apr library that is used by both Apache and the JK connector, care must be taken to use compatible versions of the packages that both use the same version of the library. It is probably safest to use the latest versions of both packages. However if that is not possible and an error similar to either of the following is seen on starting Apache/JK or Apache/JK2 respectively, then try using an earlier connector version. The change in the connector seems to have occurred between versions 1.2.5 and 1.2.6 of JK, and 2.0.2 and 2.0.4 of JK2.

Cannot load /etc/httpd/modules/mod_jk.so into server: /etc/httpd/modules/mod_jk.so: undefined symbol: apr_filepath_name_get
Cannot load /etc/httpd/modules/mod_jk2.so into server: /etc/httpd/modules/mod_jk2.so: undefined symbol: apr_socket_send

1. APACHE_HOME

   This is the location of Apache. This directory contains the modules, conf and bin sub-directories. This is dependent on where you installed Apache.

   C:\apache
                             

2. TOMCAT_HOME

   This is the location of Tomcat. The configuration, logging, work and webapps directories are all underneath this directory. This location is dependent on where you installed Tomcat.

   C:\jakarta-tomcat
                             

• edit APACHE_HOME/conf/httpd.conf

  LoadModule jk_module modules/mod_jk.so
  <IfModule mod_jk.c>
    JkWorkersFile APACHE_HOME/conf/workers.properties
    JkLogFile APACHE_HOME/logs/mod_jk.log
    JkLogLevel info
  
    # Map in the Ozibug webapp
    JkMount /ozibug/* worker1
  </IfModule>
  

• edit APACHE_HOME/conf/workers.properties

  # Define 1 real worker using ajp13
  worker.list=worker1
  # Set properties for worker1 (ajp13)
  worker.worker1.type=ajp13
  worker.worker1.host=localhost
  worker.worker1.port=8009
  worker.worker1.lbfactor=50
  worker.worker1.cachesize=10
  worker.worker1.cache_timeout=600
  worker.worker1.socket_keepalive=1
  worker.worker1.socket_timeout=300
  

• install APACHE_HOME/lib/modules/mod_jk.so

• edit TOMCAT_HOME/conf/jk2.properties

  No specific customization is required. The default file in the Tomcat distribution that has all its properties disabled is suitable for use.

• edit APACHE_HOME/conf/workers2.properties

  # Define the communication channel 
  [channel.socket:localhost:8009]
  info=Ajp13 forwarding over socket
  tomcatId=localhost:8009
  
  # Map the Ozibug webapp to the Web server uri space
  [uri:/ozibug/*]
  info=Map the whole webapp
  

  Although JK2 has many things in common with JK, the configuration is quite different, and all the directives should be inside the workers2.properties. This enables JK2 to have the same configuration file regardless of which type of web server it's connected to.

• edit APACHE_HOME/conf.d/jk2.conf

  LoadModule jk2_module modules/mod_jk2.so
  JkSet config.file /etc/httpd/conf/workers2.properties
  

• install APACHE_HOME/lib/modules/mod_jk2.so

• Stop and restart both Tomcat and Apache for the configuration changes to take effect.
• Test your installation thoroughly.
• Once successfully tested, remove (or comment out) the connector on port 8080 from the TOMCAT_HOME/conf/server.xml file. This will enhance the security of the installation. Tomcat must then be restarted again for the configuration changes to take effect.

The following steps describe the process to follow to compile the connector for Apache 2.0.40 on RedHat Linux 9.0. While the exact process for other operating systems and connector versions will vary, the basic steps should still be similar.

• Install the rpms for httpd-2.0.40-21 and httpd-devel-2.0.40-21 from the distribution CDs.
• JK
  • Download the connector source, eg., jakarta-tomcat-connectors-jk-1.2.5-src.tar.gz.
  • Unpack the source, compile and install

    $ gunzip -c jakarta-tomcat-connectors-jk-1.2.5-src.tar.gz | tar -xvf -
    $ cd jakarta-tomcat-connectors-jk-1.2.5-src
    $ cd jk/native
    $ ./configure --with-apxs=/usr/sbin/apxs
    $ (cd common; make )
    $ (cd apache-2.0; make -f Makefile.apxs )
    $ make install 
    

• JK2
  • Download the connector source, eg., jakarta-tomcat-connectors-jk2-2.0.2-src.tar.gz.
  • Unpack the source, compile and install

    $ gunzip -c jakarta-tomcat-connectors-jk2-2.0.2-src.tar.gz | tar -xvf -
    $ cd jakarta-tomcat-connectors-jk2-2.0.2-src
    $ cd jk/native2
    $ ./configure --with-apxs2=/usr/sbin/apxs
    # make jk2-build-apxs
    $ (cd server/apache2; make -f Makefile.apxs install )