Chapter 2. Load balancing with the Apache Tomcat connector (mod_jk)

Procedure

1. Go to the JBCS_HOME/httpd/conf.d directory.

2. Create a new file named mod_jk.conf and enter the following configuration details:

   # Load mod_jk module
   # Specify the filename of the mod_jk lib
   LoadModule jk_module modules/mod_jk.so
   
   # Where to find workers.properties
   JkWorkersFile conf.d/workers.properties
   
   # Where to put jk logs
   JkLogFile logs/mod_jk.log
   
   # Set the jk log level [debug/error/info]
   JkLogLevel info
   
   # Select the log format
   JkLogStampFormat  "[%a %b %d %H:%M:%S %Y]"
   
   # JkOptions indicates to send SSL KEY SIZE
   JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories
   
   # JkRequestLogFormat
   JkRequestLogFormat "%w %V %T"
   
   # Mount your applications
   JkMount /application/* loadbalancer
   
   # Add shared memory.
   # This directive is present with 1.2.10 and
   # later versions of mod_jk, and is needed for
   # for load balancing to work properly
   JkShmFile logs/jk.shm
   
   # Add jkstatus for managing runtime data
   <Location /jkstatus/>
       JkMount status
       Require ip 127.0.0.1
   </Location>

   Important

   Ensure that the LoadModule directive references the mod_jk native binary that you have installed.

   Note

   The JkMount directive specifies the URLs that the Apache HTTP Server can forward to the mod_jk module. Based on the configuration for the JkMount directive, mod_jk forwards the received URL to the correct servlet containers.

   To enable the Apache HTTP Server to serve static content (or PHP content) directly, and only use the load balancer for Java applications, the preceding configuration example specifies that the Apache HTTP Server sends only requests with the URL /application/* to the mod_jk load balancer.

   Alternatively, you can configure the Apache HTTP Server to forward all URLs to mod_jk by specifying /* in the JkMount directive.

3. Optional: To use the JkMountFile directive to specify the configuration file for a mount point, perform the following steps:

   1. Go to the JBCS_HOME/httpd/conf.d/ directory.
   2. Create a file named uriworkermap.properties.

   3. Specify the URL that you want to forward and the worker name.

      For example:

      # Simple worker configuration file
      
      # Mount the Servlet context to the ajp13 worker
      /application=loadbalancer
      /application/*=loadbalancer

      Note

      The required syntax is in the format: /URL=WORKER_NAME

      The preceding example configures mod_jk to forward requests for /application to the JBoss Web Server Tomcat back end.

   4. In the JBCS_HOME/httpd/conf.d/mod_jk.conf file, enter the following directive:

      # Use external file for mount points.
      # It will be checked for updates each 60 seconds.
      # The format of the file is: /url=worker
      # /examples/*=loadbalancer
      JkMountFile conf.d/uriworkermap.properties

4. Optional: To enable Apache HTTP Server logging, perform either of the following steps:

   • Include %w in your JkRequestLogFormat directive, as shown in the preceding step about mod_jk.conf settings.
   • Log the name of the mod_jk worker that you want to use, by including %{JK_WORKER_NAME}n in your Apache HTTP Server LogFormat(s).

Procedure

1. Go to the JBCS_HOME/httpd/conf.d/ directory.
2. Create a file named workers.properties.

3. Enter the following configuration details:

   # Define list of workers that will be used
   # for mapping requests
   worker.list=loadbalancer,status
   
   # Define Node1
   # modify the host as your host IP or DNS name.
   worker.node1.port=8009
   worker.node1.host=node1.mydomain.com
   worker.node1.type=ajp13
   worker.node1.ping_mode=A
   worker.node1.lbfactor=1
   
   # Define Node2
   # modify the host as your host IP or DNS name.
   worker.node2.port=8009
   worker.node2.host=node2.mydomain.com
   worker.node2.type=ajp13
   worker.node2.ping_mode=A
   worker.node2.lbfactor=1
   
   # Load-balancing behavior
   worker.loadbalancer.type=lb
   worker.loadbalancer.balance_workers=node1,node2
   worker.loadbalancer.sticky_session=1
   
   # Status worker for managing load balancer
   worker.status.type=status

   Note

   In the preceding example, ensure that you replace host, port, and secret settings with values that are relevant for your environment.