Load Balancing Using Apache and Mod_jk

Configure load balancing using Apache and mod_jk

1. Configure Worker Nodes in mod_jk
2. Configuring JBoss to work with mod_jk

Follow the tasks in this chapter to correctly configure load balancing using Apache and the mod_jk connector.

Task: Configure Apache to Load mod_jk
Complete this task to configure Apache to load mod_jk.

Prerequisites

    Apache and mod_jk installed .
    Open HTTPD_DIST/conf/httpd.conf and add a single line at the end of the file.
    # Include mod_jk's specific configuration file
    Include conf/mod-jk.conf

    Create a new file named HTTPD_DIST/conf/mod-jk.conf
    Add the following configuration to the mod-jk.conf file.

    Important
    The LoadModule directive must reference the mod_jk library directory location applicable to the native binary you installed.

Note :

    The JkMount directive specifies which URLs Apache should forward to the mod_jk module. Based on the directive's configuration, mod_jk forwards the received URL onto the correct Servlet containers.
    To enable Apache to serve static content (or PHP content) directly, and only use the load balancer for Java applications, the suggested configuration specifies all requests with URL path /application/* are sent to the mod_jk load-balancer.
    If you only use mod_jk as a load balancer, forward all URLs to mod_jk by specifying /* in the directive.

    # 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/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 SSK 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
        Order deny,allow
        Deny from all
        Allow from 127.0.0.1
    </Location>

    Optional: JKMountFile Directive
    In addition to the JkMount directive, you can use the JkMountFile directive to specify a mount points configuration file. The configuration file contains multiple Tomcat forwarding URL mappings.
        Navigate to HTTPD_DIST/conf.
        Create a file named uriworkermap.properties.
        Specify the URL to forward and the worker name using the following syntax example as a guide.
        The example block will configure mod_jk to forward requests to /jmx-console and /web-console to Apache.
        The syntax required takes the form /url=worker_name.

        # Simple worker configuration file

        # Mount the Servlet context to the ajp13 worker
        /jmx-console=loadbalancer
        /jmx-console/*=loadbalancer
        /web-console=loadbalancer
        /web-console/*=loadbalancer

        In HTTPD_DIST/conf/mod-jk.conf, append the following directive.

        # You can 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/uriworkermap.properties

1. Configure Worker Nodes in mod_jk

Task: Configure mod_jk Worker Nodes
Complete this task to configure two mod_jk Worker node definitions in a weighted round robin configuration with sticky sessions active between two servlet containers.

Prerequisites

    Understand the format of the workers.properties directives, as specified in Appendix A, workers.properties Reference.
    Task: Configure Apache to Load mod_jk


    Navigate to HTTPD_DIST/conf/.
    Create a file named workers.properties.
    Append the following information into the workers.properties file.

    # Define list of workers that will be used
    # for mapping requests
    worker.list=loadbalancer,status

    # Define dev1
    # modify the host as your host IP or DNS name.
    worker.dev1.port=8009
    worker.dev1.host=dev1.srinivaslinux.com
    worker.dev1.type=ajp13
    worker.dev1.ping_mode=A
    worker.dev1.lbfactor=1

    # Define dev2
    # modify the host as your host IP or DNS name.
    worker.dev2.port=8009
    worker.dev2.host=dev2.srinivaslinux.com
    worker.dev2.type=ajp13
    worker.dev2.ping_mode=A
    worker.dev2.lbfactor=1

    # Load-balancing behavior
    worker.loadbalancer.type=lb
    worker.loadbalancer.balance_workers=dev1,dev2
    worker.loadbalancer.sticky_session=1

    # Status worker for managing load balancer
    worker.status.type=status

Good Luck :)