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

Procedure

1. Go to the Apache HTTP Server configuration directory:

   • If you are using the JBCS Apache HTTP Server, go to the JBCS_HOME/httpd/conf.d directory.
   • If you are using the RHEL Apache HTTP Server, go to the /etc/httpd/conf.d directory.
2. Open the mod_proxy_cluster.conf file.

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

   Listen IP_ADDRESS:PORT_NUMBER

   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.

4. To create a virtual host, enter the following details in the mod_proxy_cluster.conf file:

   <VirtualHost IP_ADDRESS:PORT_NUMBER>
      DirectoryIndex disabled
      <Location />
         Require ip IP_ADDRESS
      </Location>
   
      KeepAliveTimeout 60
      MaxKeepAliveRequests 0
   
      ManagerBalancerName mycluster
      AdvertiseFrequency 5
      EnableMCMPReceive On
   
      <Location /mod_cluster_manager>
         SetHandler mod_cluster-manager
         Require ip IP_ADDRESS
      </Location>
   
   </VirtualHost>

   Important

   If you specify the EnableMCMPReceive directive in your virtual host, the Apache HTTP Server requires that you always use Location elements rather than Directory elements in the virtual host definition. From JBCS 2.4.62 onward, the Apache HTTP Server does not support the use of Directory elements and the EnableMCMPReceive directive within the same virtual host. If you specify a Directory element and the EnableMCMPReceive directive within the same virtual host, the Apache HTTP Server fails to start and logs an error indicating that you should use a Location element instead. The startup failure was introduced in JBCS 2.4.62 as a breaking change that is not compatible with earlier releases.

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

Procedure

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

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

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

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

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

   Note

   JBoss Web Server 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 RHEL:

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

   • For Windows Server 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"'

     Note

     When a proxy server uses mod_proxy_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_proxy_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"/>

   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"/>