Apache and Tomcat With mod_jk Installation and Configuration

What is Apache Tomcat?
Apache Tomcat is the servlet container that is used in the official Reference Implementation for the Java Servlet and JavaServer Pages technologies.

Apache Tomcat powers numerous large-scale, mission-critical web applications across a diverse range of industries and organizations

What is mod_jk?

mod_jk is a replacement to the elderly mod_jserv. It is a completely new Tomcat-Apache plug-in that handles the communication between Tomcat and Apache.

Why mod_jk?

Several reasons

mod_jserv was too complex. Because it was ported from Apache/JServ, it brought with it lots of JServ specific bits that aren’t needed by Apache.

mod_jserv supported only Apache. Tomcat supports many web servers through a compatibility layer named the jk library. Supporting two different modes of work became problematic in terms of support, documentation and bug fixes. mod_jk should fix that.

The layered approach provided by the jk library makes it easier to support both Apache1.3.x and Apache2.xx.
Better support for SSL. mod_jserv couldn’t reliably identify whether a request was made via HTTP or HTTPS. mod_jk can, using the newer Ajpv13 protocol.

Apache2 Installation and Configuration

For apache2 Installation click here and we will see now some configuration

Edit /etc/apache2/apache2.conf. Change

DirectoryIndex index.html index.cgi index.pl index.php index.xhtml

to

DirectoryIndex index.html index.htm index.shtml index.cgi index.php index.php3 index.pl index.xhtml

Edit /etc/mime.types and comment out the following lines:

Edit /etc/apache2/ports.conf and add Listen 443

Now we have to enable some Apache modules (SSL, rewrite and suexec):

Restart Apache:

Installing JDK in Debian

In order to run Tomcat, you will need to install JDK and set the JAVA_HOME environment variable to identify the location of the JDK environment on your system.

1. You can download JDK 5.0 at http://java.sun.com/j2se/1.5.0/download.jsp.

2. Click on Download JDK 5.0 Update 6 to go to the download page.

3. Click Accept to accept the license agreement.

4. Next choose the Linux self-extracting file. This is the download for the self-extracting binary file rather than the rpm.

5. Download to your preferred download directory. Change to that directory and make it executable by executing the following command

#chmod +x jdk-1_5_0_06-linux-i586.bin

Now execute the file:

#./jdk-1_5_0_06-linux-i586.bin

You should now have a new directory called jdk1.5.0_06. Now move this directory to the location where it should be run. We chose /usr/lib/.

#mv jdk1.5.0_06 /usr/lib

Now create a symbolic link called jdk to JAVA_HOME by the following command. This allows you to easily switch back and forth between different jvms should you ever need to.

#cd /usr/lib

#ln -s jdk1.5.0_06 jdk

Now we need to set the JAVA_HOME environment variable. Add the following at the end of /etc/profile just after export PATH.

JAVA_HOME=”/usr/lib/jdk”
export JAVA_HOME

/etc/profile is executed at startup and when a user logs into the system. In order to update the environment you will need to log out and log back in to the system.

Check to make sure JAVA_HOME is defined correctly by executing the command below. This should report the location of the Java SDK which should be /usr/lib/jdk.

echo $JAVA_HOME

Installing Tomcat in Debian Linux

In this section you will download and install Apache Tomcat 5.5.16. For this particular setup, there is no need to build the package from source, we will download the binary version.

1. Download the binary version to your preferred download directory from here: http://tomcat.apache.org/download-55.cgi. Choose the tar.gz from the core section for 5.5.16.

2. Now change to that directory and extract the files using the following command:

#cd /downloads #(be sure to change to your download directory)

#unp apache-tomcat-5.5.16.tar.gz

You should now have a new directory called apache-tomcat-5.5.16. Now move this directory to the location where it should be installed. Again, We chose /usr/lib/. Note that this location will be referred to as CATALINA_HOME in the Tomcat documentation.

#mv apache-tomcat-5.5.16 /usr/lib

3. Next change to the /usr/lib/ directory.

#cd /usr/lib

4. Now create a symbolic link called apache-tomcat to the CATALINA_HOME by the following command.

#ln -s apache-tomcat-5.5.16 apache-tomcat

This will save you from having to make changes to startup and shutdown scripts each time you upgrade Tomcat and if you so desire, it also allows you to keep several versions of Tomcat on your system and easily switch amongst them.

You should now be able to start and stop Tomcat from the CATALINA_HOME/bin directory. If you are using another shell other than the bash shell you will nee to add sh to the beginning of the command. You should now be able to test that Tomcat is installed by starting it and opening yourbrowser and entering http://localhost:8080 into your browser. Port 8080 is the default port for Tomcat and can be easily changed in the /usr/lib/apache-tomcat/conf/server.xml file. (We will work with this file later on.) If you plan to access this page remotely, be sure to forward the respective port to your server’s IP address within your router. You should now see the Tomcat welcome page that contains links to Tomcat documentation as well as sample JSP/Servlet scripts. Verify that Tomcat is running by executing some of the examples found on the welcome page.

#cd /usr/lib/apache-tomcat/bin

#./startup.sh

To shutdown the server, you will need to execute the following command. Feel free to try it, but for now we will leave Tomcat running.

#./shutdown.sh

Installing and configuring mod_jk 

In order to make the connection between Tomcat and Apache, we will need to download and install mod_jk connector. You will find that the Apache documentation recommends that you install the packaged version of mod_jk if it is available for your particular Linux distribution. Many outdated resources recommend installing the mod_jk2 connector, but we have found that it has been deprecated and although mod_jk was developed before mod_jk2, it is still fully supported and is very stable.

1. Download the current source from the Apache archives:

http://archive.apache.org/dist/jakarta/tomcat-connectors/jk/source/jk-1.2.15/.

Download the jakarta-tomcat-connectors-1.2.15-src.tar.gz file to your /usr/src/ directory.

2. Change to the /usr/src directory.

#cd /usr/src

3. Next, extract the contents to create the /usr/src/jakarta-tomcat-connectors-1.2.15-src directory.

#unp jakarta-tomcat-connectors-1.2.15-src.tar.gz

4. Change to the /usr/src/jakarta-tomcat-connectors-1.2.15-src/jk/native directory.

#cd jakarta-tomcat-connectors-1.2.15-src/jk/native

5. Now you are ready to create the custom configure file for your system. Execute the following:

#./buildconf.sh

This will create a configure file in the /usr/src/jakarta-tomcat-connectors-1.2.15-src/jk/native directory.

6. Execute the following command in order to configure mod_jk for your system.
Important note: You will need to have apxs2 (APache eXtension tool) installed and configured with Apache. If you do not have it, as was my case, you can download and install the apache2-threaded-dev package (which replaced the former apache-dev package) from www.debian.org. At the time of this writing, the Debian package archive at www.debian.org was down and they referred me to their temporary site until they resolved their issues pdo.debian.net. I found the apache2-threaded-dev package and was able to install it successfully.

Be sure to include the correct location apxs2 on your system in the path of the command.

#./configure –with-apxs=/usr/bin/apxs2

7. Now build the mod_jk with the following:

#make

8. Finally, if you were successful with the previous commands, copy the newly created mod_jk.so to your Apache2 modules directory. My modules were located at /usr/lib/apache2/modules.

#cd apache-2.0

#cp /usr/src/jakarta-tomcat-connectors-1.2.15-src/jk/native/apache-2.0/mod_jk.so /usr/lib/apache2/modules

You now are ready to move to the next stage which is to begin configuring Apache and Tomcat. You can find more information about the mod_jk connector here http://tomcat.apache.org/connectors-doc/howto/apache.html.

Configuring Tomcat and Apache 

Create the workers.properties file.

Important note: Be sure to make a backup copy of your config files before modifying.
The workers.properties file contains the details about how each process is linked to Tomcat by defining workers that communicate through the ajpv13 protocol. Refer to the Workers HowTo for more detail.

1. First create the workers.properties file in your Apache2 root directory.

#touch /etc/apache2/workers.properties

2. Next, open the workers.properties file and add the following. You can find many other examples of the workers.properties file on the internet, but this is the one that I created and it seems to work fine with the other portions that have already been configured in this tutorial.

3. Save and close the file.

4. Now we need to open the /etc/apache2/apache2.conf file and add the following lines at the bottom. (httpd.conf is just for backward compatibility):

Save and close the file.Now a final security point.

We will create a group and user tomcat tomcat like that:

#groupadd tomcat

#useradd -g tomcat tomcat

Then change the user and group of the Tomcat path:

#chown -R tomcat:tomcat /usr/lib/apache-tomcat-5.5.16

To change the password of tomcat user, with root type:

#passwd tomcat

and follow the instructions.

Then to start and stop the Tomcat server you should use the tomcat user.

#su – tomcat

Now stop and start Tomcat:

#cd /usr/lib/apache-tomcat/bin

#./shutdown.sh

#./startup.sh

And restart Apache:

#/etc/init.d/apache2 restart

Testing Your Installation

In this test, we are directing all URLs that begin with “/jsp-examples” to Tomcat.
In a real world situation, we might only direct JSPs or servlets to the JK worker.

Make sure no other server is running on the default Tomcat ports of 8005, 8009 and 8080.
Make sure no other server is running on the Apache port, which is normally 8080 or 80.

Start Tomcat first: Always start Tomcat first and then start Apache.
If you have to bounce Tomcat, remember to take down Apache first and restart it after Tomcat restarts.
Start Apache: Point your browser to http://localhost and verify that you get the default Apache page. Substitute “localhost” for the actual machine name/IP if necessary.

Point your browser to http://localhost:8080 and verify that you get the default Tomcat page.

Point your browser to http://localhost/jsp-examples/ and verify that you get the index page for the Tomcat examples.

This will be served by Apache and will indicate that you have completed your integration of Apache and Tomcat successfully.

Important References and paths

Tomcat conf

/usr/lib/apache-tomcat/conf/server.xml

Tomcat stop and start

cd /usr/lib/apache-tomcat/bin
./shutdown.sh
./startup.sh

Apache modules

/usr/lib/apache2/modules

Apache conf

/etc/apache2/workers.properties
/etc/apache2/apache2.conf
/etc/apache2/httpd.conf

Apache2

/etc/init.d/apache2 restart
/etc/init.d/apache2 stop
/etc/init.d/apache2 start