Configuring simple load balancing across multiple application server profiles with an administrative agent using a job manager

Simple load balancing distributes HTTP requests across multiple IBM® WebSphere® Application Server instances. You can configure simple load balancing to provide failover of an application state that is maintained in an HTTP session.

1. Install WebSphere Application Server and create application server profiles.
   For more information, see the documentation on WebSphere Application Server installation and application server profiles.
2. Configure the administrative agent and register each application server profile with the administrative agent.
   Complete the following steps:

   1. Set up the administrative agent, which includes creating the administrative agent profile.
   2. Register the stand-alone application server with the administrative agent.
   3. Start and stop the administrative agent.

   After you complete these steps, you can complete all the administrative operations through the administrative agent. When you log in to the administrative console for the administrative agent, you can select which application servers to manage. For more information, see the documentation on administering stand-alone nodes using the administrative agent.

3. Install WebSphere Application Server Network Deployment for the licensed WebSphere Application Server Network Deployment instances that will perform centralized management for the stand-alone application server instances.
   For more information, see the installation documentation for the WebSphere Application Server Network Deployment product.

   Attention: You must access the documentation for WebSphere Application Server Network Deployment to read its installation documentation.
4. Create the job manager profile, configure the job manager, and register stand-alone application servers with the job manager.
   For more information, see the documentation on setting up a job manager environment.
   You can complete administrative options centrally using the job manager. For more information about the job manager, see the conceptual information about the job manager.
5. Install the enterprise application or web module.
   You can use one of the following methods to install the enterprise application or web module:

   • Install the enterprise application or web module on each application server. For more information, see the documentation on installing enterprise applications or modules.
   • Install the enterprise application or web module using the job manager. For more information, see the documentation on installing applications using the job manager.
6. Determine if you require session affinity.

   Session affinity directs requests from a given client to a specific application server. The application state maintained in the HTTP session is accessed in the HTTP session cache, which is local to the application server. Session affinity provides higher performance than database persistence of the session object, alone. Without session affinity, session requests must be obtained from the database if they are sent to a server that does not have the session object in the local cache.

7. Optional: Configure a unique HTTP session clone ID for each application server.
   You must complete this step if you require session affinity.

   You can configure a unique HTTP session clone ID using wsadmin scripting or the administrative console. To use wsadmin commands for the Jython or Jacl programming language, see the documentation on configuring a unique HTTP session clone ID for each application server using scripting. To configure a unique HTTP session clone ID using the administrative console, complete the following steps:

   1. Expand Servers > Server Types and click WebSphere application servers > server_name.
   2. Under Container Settings, expand Web Container Settings and click Web container.
   3. Under Additional Properties, click Custom properties > New.
   4. In the Name field, enter HttpSessionCloneId.
   5. In the Value field, enter a unique value for each server. The unique value must be 8 - 9 alphanumeric characters; for example, test1234
   6. Click Apply or OK.
   7. Click Save to save the configuration changes to the master configuration.
8. Optional: Configure session persistence.
   If you require session failover capability, you must configure session persistence. Persistence of the session object to a database is the only option for session failover with WebSphere Application Server. To configure session persistence using the administrative console, see the documentation on configuring database session persistence. To configure database session persistence using wsadmin commands for the Jython or Jacl programming language, see the documentation on configuring database session persistence using scripting.
9. Restart the server.
10. Generate the plugin-cfg.xml file for each stand-alone application server using the GenPluginCfg script, the administrative console, or wsadmin scripting.

    To use the GenPluginCfg script, enter the following command on the command line:profile_root/config/cells/GenPluginCfg.sh|bat

    To use the administrative console, see the documentation on creating or updating a global web server plug-in configuration file.

    The following variables apply to the Jython and Jacl commands:

    • cell_name is the name of your cell.
    • web_server_node is the name of the node for your web server.
    • web_server_name is the name of your web server.

    Jython

    On the command line, enter each of the following commands on a separate line:

    generator = AdminControl.completeObjectName('type=PluginCfgGenerator,*')
    AdminControl.invoke(generator, 'generate', "profile_root/config cell_name web_server_node web_server_name true true")

    Jacl

    On the command line, enter each of the following commands on a separate line:

    set generator [$AdminControl completeObjectName type=PluginCfgGenerator,*]
    $AdminControl invoke $generator generate "profile_root/config cell_name web_server_node web_server_name true true"

11. Merge the plugin-cfg.xml files from multiple application server nodes.
    You can either manually merge the plugin-cfg.xml files or use the tool to automatically merge the plugin-cfg.xml file from multiple application server profiles into a single output file. The .bat or .sh tool is available after you install this fix pack and is located in the install_root/bin directory. To use the tool, complete the following steps:

    1. Rename the plugin-cfg.xml files to a unique name across your application server profiles.
    2. Copy the plugin-cfg.xml file for all stand-alone application server profiles into a common directory.
    3. Use the tool to combine the plugin-cfg.xml files from each of the application server profiles into a single output file. For example:

       install_root/bin/.sh plugin_configuration_file1 plugin_configuration_file2 resulting_plugin_configuration_file

       

       install_root\bin\.bat plugin_configuration_file1 plugin_configuration_file2 resulting_plugin_configuration_file

       The resulting_plugin_configuration_file variable value is normally plugin-cfg.xml

    For more information about manually merging the plugin-cfg.xml files, see the technote on merging plugin-cfg.xml files from multiple application server profiles.

12. Copy the merged plugin-cfg.xml file to the plugin_installation_root/config/web_server_name/ directory on the Web server host.
13. Ensure that you have defined the correct operating system file access permissions for the merged plugin-cfg.xml file.
    These file access permissions allow the HTTP server plug-in process to read the file.