When using a hardware loadbalancer you can leverage from the ability of mod_cluster to calculate server-side load metrics to determine how best to balance requests.
 
By default, these metrics are not accessible from outside of mod_cluster, but a minor code change to the distribution allows you to access this so called “loadbalance factor” through JMX. A healthcheck servlet could access this information and provide this to the hardware load balancer.
 
Follow the steps below to modify your mod_cluster distribution to enable additional JMX information:
 
# Download the mod_cluster source (version 1.0.10-GA was used in combination with JBoss EAP 5.1.x) {code}
$ svn co http://anonsvn.jboss.org/repos/mod_cluster/tags/1.0.10.GA
{code}
# Update the pom.xml to include additional repository for trove (see: [this post|https://community.jboss.org/message/625343]) {code:xml}
<repository>
          <id>maven-nuxeo</id>
          <name>Maven Nuxeo Repository</name>
          <url>https://maven.nuxeo.org/nexus/content/groups/public/</url>
          <layout>default</layout>
          <releases>
                    <enabled>true</enabled>
                    <updatePolicy>never</updatePolicy>
          </releases>
          <snapshots>
                    <enabled>true</enabled>
                    <updatePolicy>never</updatePolicy>
          </snapshots>
</repository>
{code}
# Verify the non-patched mod_cluster build process; skip the tests as you might run into issues with your local firewall {code}
$ mvn -P dist package -Dmaven.test.skip=true
{code}
# You will find the mod_cluster SAR under the target/ directory: {code}
mod-cluster.sar/
├── META-INF
│   └── mod-cluster-jboss-beans.xml
└── mod-cluster-1.0.10.GA.jar
 
1 directory, 2 files
{code}
# Edit src/main/java/org/jboss/modcluster/load/impl/DynamicLoadBalanceFactorProviderMBean.java and add to the MBean interface: {code}
   /**
    * Returns the loadbalance factor
    * @return a positive integer
    */
   int getLoadBalanceFactor();
{code}
# Run the maven task again {code}
$ mvn -P dist package -Dmaven.test.skip=true
{code}
# Install the mod_cluster server components to your JBoss installation by copying the mod_cluster.sar exploded archive to SERVER_HOME/deploy directory
# Follow the instructions for the Lifecycle listener [here|http://docs.jboss.org/mod_cluster/1.0.0/html/javaconf.html] 
# Enable the load metrics as described [here|http://docs.jboss.org/mod_cluster/1.0.0/html/javaload.html|here]

Last, but not least, you can get the loadbalancer factor through JMX when browsing to: jboss.web:LoadbalancerProvider.