Chapter 3. Load balancing with the JBoss HTTP connector (mod_cluster)

Procedure

1. Open the mod_cluster configuration file.

   Note

   The mod_cluster configuration file is typically located in the JBCS_HOME/httpd/conf.d/mod_cluster.conf directory.

2. To create a Listen directive for the proxy server, enter the following line in the mod_cluster.conf file:

   Listen IP_ADDRESS:PORT_NUMBER

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   Note

   In the preceding example, replace IP_ADDRESS with the address of the server network interface that the proxy server uses to communicate with the worker nodes, and replace PORT_NUMBER with the port that the proxy server listens on.

   Ensure that the port is open for incoming TCP connections.

3. To create a virtual host, enter the following details in the mod_cluster.conf file:

   <VirtualHost IP_ADDRESS:PORT_NUMBER>
   
      <Directory />
         Require ip IP_ADDRESS
      </Directory>
   
      KeepAliveTimeout 60
      MaxKeepAliveRequests 0
   
      ManagerBalancerName mycluster
      AdvertiseFrequency 5
      EnableMCPMReceive On
   
   </VirtualHost>

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   Note

   In the preceding example, replace IP_ADDRESS and PORT_NUMBER with the address of the server network interface and port number that you have specified for the Listen directive.

   This address and port combination is only used for mod_cluster management messages. This address and port combination is not used for general traffic.

Procedure

1. To add a listener to Tomcat, add the following Listener element below the other Listener elements in the JWS_HOME/tomcat<VERSION>/conf/server.xml file:

   <Listener className="org.jboss.modcluster.container.catalina.standalone.ModClusterListener" advertise="true" stickySession="true" stickySessionForce="false" stickySessionRemove="true" />

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2. To give the worker node a unique identity, edit the JWS_HOME/tomcat<VERSION>/conf/server.xml file, to add the jvmRoute attribute and value to the Engine element:

   <Engine name="Catalina" defaultHost="localhost" jvmRoute="worker01">

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3. To configure STATUS MCMP message frequency, modify the org.jboss.modcluster.container.catalina.status-frequency Java system property.

   For example:

   -Dorg.jboss.modcluster.container.catalina.status-frequency=6

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   Note

   Tomcat worker nodes periodically send status messages that contain their current load status to the Apache HTTP Server balancer. The default frequency of these messages is 10 seconds. If you have hundreds of worker nodes, the STATUS MCMP messages can increase traffic congestion on your Apache HTTP Server network.

   You can configure the MCMP message frequency by modifying the org.jboss.modcluster.container.catalina.status-frequency Java system property. By default, the property accepts values that are specified in seconds multiplied by 10. For example, setting the property to 1 means 10 seconds. In the preceding example, the property is set to 6, which means 60 seconds.

4. Optional: To configure the firewall for proxy server advertisements, complete either of the following steps to open port 23364 for UDP connections on the worker node’s firewall:

   • For Red Hat Enterprise Linux 7:

     firewall-cmd --permanent --zone=public --add-port=23364/udp

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   • For Microsoft Windows using PowerShell

     Start-Process "$psHome\powershell.exe" -Verb Runas -ArgumentList '-command "NetSh Advfirewall firewall add rule name="UDP Port 23364" dir=in  action=allow protocol=UDP localport=23364"'
     Start-Process "$psHome\powershell.exe" -Verb Runas -ArgumentList '-command "NetSh Advfirewall firewall add rule name="UDP Port 23364" dir=out action=allow protocol=UDP localport=23364"'

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     Note

     When a proxy server uses mod_cluster, the proxy server can use UDP multicast to advertise itself. Most operating system firewalls block the server advertisement feature by default. To enable server advertisement and receive these multicast messages, you can open port 23364 for UDP connections on the worker node’s firewall, as shown in the preceding examples.

Procedure

1. Open the JWS_HOME/tomcat<VERSION>/conf/server.xml file.

2. To define a mod_cluster listener and disable dynamic proxy discovery, add or change the Listener element for ModClusterListener.

   For example:

   <Listener className="org.jboss.modcluster.container.catalina.standalone.ModClusterListener" advertise="false" stickySession="true" stickySessionForce="false" stickySessionRemove="true"/>

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   Note

   Ensure that you set the advertise property to false.

3. To create a static proxy server list, update the proxyList property by adding a comma-separated list of proxies in the following format: IP_ADDRESS:PORT,IP_ADDRESS:PORT

   For example:

   <Listener className="org.jboss.modcluster.container.catalina.standalone.ModClusterListener" advertise="false" stickySession="true" stickySessionForce="false" stickySessionRemove="true" proxyList="10.33.144.3:6666,10.33.144.1:6666"/>

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