19.4.3. Disable Advertising for the mod_cluster Subsystem

By default, the mod_cluster subsystem's balancer uses multicast UDP to advertise its availability to the background workers. If you wish, you can disable advertisement. Use the following procedure to configure this behavior.

Procedure 19.6. 

  1. Modify the httpd configuration.

    Modify the httpd configuration to disable server advertising and to use a proxy list instead. The proxy list is configured on the worker, and contains all of the mod_cluster-enabled Web servers the worker can talk to.
    The mod_cluster configuration for the Web server is typically located in /etc/httpd/ or the etc/httpd/ directory within the httpd installation, if it is installed in a non-standard location. Refer to Section 19.5.3, “Install the mod_cluster Module Into Apache HTTP Server or JBoss Enterprise Web Server (Zip)” and Section 19.5.5, “Configure Server Advertisement Properties for Your mod_cluster-enabled Web Server” for more information about the file itself. Open the file containing the virtual host which listens for MCPM requests (using the EnableMCPMReceive directive), and disable server advertising by changing the ServerAdvertise directive as follows.
    ServerAdvertise Off
  2. Disable advertising within the mod_cluster subsystem of JBoss EAP 6, and provide a list of proxies.

    You can disable advertising for the mod_cluster subsystem and provide a list of proxies, by using the web-based Management Console or the command-line Management CLI. The list of proxies is necessary because the mod_cluster subsystem will not be able to automatically discover proxies if advertising is disabled.
    • Management Console

      If you use a managed domain, you can only configure mod_cluster in profiles where it is enabled, such as the ha and full-ha profiles.
      1. Log in to the Management Console and select the Configuration tab at the top of the screen. If you use a managed domain, select either the ha or full-ha profile from the Profile drop-down menu at the top left.
      2. Expand the Subsystems menu then expand the Web menu and select mod_cluster.
      3. Click Edit under the Advertising tab under mod_cluster. To disable advertising, clear the check box next to Advertise, and click Save.
        mod_cluster Advertising Configuration Screen

        Figure 19.1. mod_cluster Advertising Configuration Screen

      4. Click the Proxies tab. Click Edit and enter a list of proxy servers in the Proxy List field. The correct syntax is a comma-separated list of HOSTNAME:PORT strings, like the following:
        10.33.144.3:6666,10.33.144.1:6666
        Click the Save button to finish.
    • Management CLI

      The following two Management CLI commands create the same configuration as the Management Console instructions above. They assume that you run a managed domain and that your server group uses the full-ha profile. If you use a different profile, change its name in the commands. If you use a standalone server using the standalone-ha profile, remove the /profile=full-ha portion of the commands.
      /profile=full-ha/subsystem=modcluster/mod-cluster-config=configuration/:write-attribute(name=advertise,value=false)
      
      /profile=full-ha/subsystem=modcluster/mod-cluster-config=configuration/:write-attribute(name=proxy-list,value="10.33.144.3:6666,10.33.144.1:6666")
Result

The httpd balancer no longer advertises its presence to worker nodes and UDP multicast is no longer used.