4.2.  Use the standard set of command line administrative tools such as wsadmin, profile management and plug-in generation.

[Note]
  • [WAS_8.5_INFOCENTER] Configuring simple load balancing across multiple application server profiles

Configuring simple load balancing across multiple application server profiles

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.

You can configure simple load balancing capability with WebSphere Application Server by combining the plug-in configuration files of multiple stand-alone application server profiles into a single configuration file. The number of configuration files that you can combine are bound by the limits that exist in the WebSphere Application Server license agreement. You can use the following different configurations of the application server to combine the plug-in configuration files of multiple application server profiles into a single output file:

Complete the following steps to configure simple load balancing across multiple stand-alone, base application server profiles:

  1. Install WebSphere Application Server and create application server profiles.

  2. Install the enterprise application or web module.

  3. 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.

  4. 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.sh scripting or the administrative console. 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 the 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.

  5. Optional: Configure session persistence, if needed. 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 database session persistence using wsadmin commands for the Jython or Jacl programming language.

  6. Restart the server.

  7. Generate the plugin-cfg.xml file for each application server using the GenPluginCfg.sh script, the administrative console, or wsadmin.sh scripting.

  8. Merge the plugin-cfg.xml files from multiple application server nodes.

    You can either manually merge the plugin-cfg.xml files or use the pluginCfgMerge tool to automatically merge the plugin-cfg.xml file from multiple application server profiles into a single output file. The pluginCfgMerge.bat and pluginCfgMerge.sh files are located in the install_root/bin directory.

    To use the pluginCfgMerge 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 pluginCfgMerge.sh 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/pluginCfgMerge.sh plugin_configuration_file1 plugin_configuration_file2 plugin-cfg.xml
      											

  9. Copy the merged plugin-cfg.xml file to the plugin_installation_root/config/web_server_name/ directory on the web server host.

  10. 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.

When you complete this process, you have one plug-in configuration file for multiple stand-alone application server profiles.

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