Apache Jserv protocol

This protocol was mainly developed to transfer data over the network in binary format instead of plain text. It uses TCP and a packet-based protocol, hence, increasing the performance of the web servers. Another informational point is that decryption of requests is done on the web server end so that the application server doesn't have a high load.

Note

If you are using AJP, the network traffic is reduced, as the tariff passes over the TCP protocol.

mod_jk and mod_proxy are based on the AJP protocol. They are also helpful in transmitting a high content response over the browser.

Note

If we use the latest version of mod_jk for integration of Apache and Tomcat, then we can store the response header of 64k in the web browsers. This process is very useful in the case of SSO enabled applications or storing Java session values in the browser.

Installation and configuration of mod_jk

mod_jk is an AJP connector which is used to integrate web servers such as Apache or IIS to Tomcat 7. In case we don't install mod_jk, then we cannot use frontend web servers for Tomcat. This module is very helpful in order to hide Tomcat behind the frontend web server and also eliminates the port number while browsing the URL. It involves multiple steps starting from installation and configuration. Let's first discuss the installation of mod_jk.

Installation of mod_jk

The mod_jk source can be downloaded from its official site, http://tomcat.apache.org/download-connectors.cgi. It is always recommended to download the latest stable version from the site for the implementation.

  1. Once the source is downloaded we have to extract it in the server directory using the following command:
    [root@localhost opt]# tar -zxvf tomcat-connectors-1.2.x-src.tar
    • where x is the minor version number.
  2. Once the code is extracted, a directory is created in the current path named as tomcat-connectors-1.2.32. It's the home directory of the mod_jk source. The following screenshot shows the extracted code in the tomcat-connectors-1.2.32 directory, which is created after the execution of the previous command:
    Installation of mod_jk
  3. Go to the native directory of the mod_jk source using the following command and then run the configure command:
    [root@localhost opt]# cd /opt/tomcat-connectors-1.2.32-src/native ./configure --with-apxs=/opt/apache-2.2.19/bin/apxs

    Tip

    Tip for configuration

    mod_jk is specific to the Apache version and the Apache Extension Tool (APXS) should be used for the current version of Apache, which we will use in the environment.

    Once mod_jk is compiled on one server, there is no need to generate for another Apache instance. It can be directly copied to the other instance.

    This trick is tested on Linux only.

  4. The following screenshot shows the installation process using the APXS module. Installation of mod_jk begins by running the configure command:
    Installation of mod_jk
  5. Once the configuration is done, you need to run the make command, which compiles the source code, as shown in the following screenshot:
    [root@localhost apache-2.0]# make
    Installation of mod_jk
  6. After the code is compiled using the make command then installation of the code is done using the command make install:
    root@localhost apache-2.0]# make install
    Installation of mod_jk
  7. Once the execution is complete, it will create the module in the apache-2.0 directory of the source, as shown in the following screenshot:
    Installation of mod_jk

Configuration of mod_jk in Apache

Configuration of mod_jk is a little complicated in Apache. There are various ways of performing the configuration, but the most commonly used option is the concept of creation of workers.properties and mod_jk.conf. The steps to be performed are mentioned below:

  1. Copy the mod_jk.so from the apache 2.0 directory of the connector source to the modules directory of the Apache httpd server by using the following command:
    [root@localhost apache-2.0]# cp mod_jk.so /opt/apache-2.2.19/modules/
chmod 755 mod_jk.so
    • The previous command sets the execution permission.
      chown root:root mod_jk.so
    • The previous command sets the the ownership to root.
  2. To edit the configuration of the httpd server, you have to create the new file called as mod_jk.conf in the conf directory of $APACHE_HOME/conf as follows:
    [root@localhost apache-2.0]# cd /opt/apache-2.2.19/conf
vi mod-jk.conf
LoadModule jk_module modules/mod_jk.so
JkWorkersFile conf/workers.properties
JkLogFile logs/mod_jk.log
JkLogLevel info
JkMount /sample/* node1

    The mod_jk.conf file contains the following details:

    • Module path: It defines the location of the module from where Apache loads the module during the startup process, for example, LoadModule jk_module modules/mod_jk.so.
    • Worker file path: It defines the location of the worker file, this file contains the information of the Tomcat instance details such as the IP, port and load balancing methods such as JkWorkersFile conf/workers.properties.
    • Log file: It records the activity for Apache Tomcat integration, it also records the connectivity health check run between Apache/Tomcat (JkLogFile logs/mod_jk.log).
    • URL mapping: It defines the context path for Apache and also sets the rules such as redirecting the request if you get any request with the defined URL, for example, JkMount /sample/* node1. This means whenever the user hit the URL http://localhost/sample, the request will redirect to the Tomcat node1.
    • Log level: This parameter captures the different events performed by mod_jk in the logs (JkLogLevel info).
    Configuration of mod_jk in Apache
  3. Create a new file named as workers. properties in the conf using the following command:
    [root@localhost conf]# vi workers.properties
worker.list=node1
worker.node1.port=8009
worker.node1.host=10.130.240.51
worker.node1.type=ajp13
worker.node1.lbfactor=1

    workers.properties contain the following details:

    • Node name (common name for the host)
    • AJP port details for Tomcat (the port on which Tomcat accepts the request for AJP)
    • Host IP for Tomcat (the IP address where the Tomcat instance is running)
    • Protocol used (the protocol used for communication by default is AJP)
    • Load balancing method (Round robin, persistence, and so on)
    Configuration of mod_jk in Apache
  4. The last step is to include the mod_jk.conf in the main configuration file of the httpd, that is, httpd.conf.
    [root@localhost conf]# vi httpd.conf

    Note

    Include conf/mod_jk.conf should be added at the end of httpd.conf.

Now we are done with configuration of mod_jk in the Apache HTTP configuration file (httpd.conf). But mod_jk will not work until we recycle the Apache httpd services. So why wait? Let's recycle by running the following command:

[root@localhost bin]# ./apachectl stop
[root@root@localhost bin]# ./apachectl start

Note

In case the Apache services are not displayed after the configuration, then we will run the configtest.sh placed in the bin directory that shows the issues with configuration.

Once we are done with the Apache web server configurations, followed by the web server service restart, it's now time to test the application. In Chapter 1, Installation of Tomcat 7, we had tested the application by using the host and port number on which Tomcat services were running http://localhost:8080/applicationname, as shown in the following screenshot:

Configuration of mod_jk in Apache

After enabling the mod_jk configuration, you can check the URL without using the port number (http://localhost/applicationname). The following screenshot shows the application with the application's URL:

Configuration of mod_jk in Apache

mod_proxy configuration

mod_proxy configuration is very simple as compared to mod_jk configuration. Here, we need to add the module and redirect the URL to a virtual host.

Open the httpd.conf and place the following entry:

  1. Place the following lines of code after the other LoadModule directives:
    LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
  2. Place the following lines of code with your other VirtualHost, or at the bottom of the file:
    NameVirtualHost *
<VirtualHost *>
ServerName abc.com
ProxyRequests Off
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
ProxyPass / http://localhost:8080/
ProxyPassReverse / http://localhost:8080/
<Location />
Order allow,deny
Allow from all
</Location>
</VirtualHost>

Save the configuration file. Based on the Rule of Thumb, every configuration change is reflected only after a recycle. 

[root@localhost bin]# ./apachectl stop
[root@root@localhost bin]# ./apachectl start

Comparison between mod_jk and mod_proxy

We have discussed mod_jk and mod_proxy but we still don't know when to use which module to increase the speed of the web server. Let's compare both modules and find out which can be used in a real-time environment:

Feature

mod_jk

mod_proxy

Load balancing

High level

Basic

Management interface

Yes

No

Compilation

Separate process

Not required. By default comes with Apache

Configuration

Huge

Basic

Protocol

AJP

HTTP/HTTPS/AJP

Node failure

Advance

NA

The previous table shows the comparison of mod_jk and mod_proxy. Based on the features, the web administrator can decide which module should be used.

Note

In 90 percent of cases, mod_jk is used with Apache Tomcat

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