Wildfly. Configure load balancing metrics

06 August 2019

Previously i wrote about Wildfly domain mode cluster and load balancing from the box. But what if we would like to do balancing depends on specific server behavior ?

Wildfly subsystem mod_cluster provide us several predefined metric types to determine best request balancing:

cpu: based on CPU load
mem: based on system memory usage
heap: based on heap usage
sessions: based on number of web sessions
requests: based on amount of requests/sec
send-traffic: based on outgoing requests traffic
receive-traffic: based on incoming requests POST traffic
busyness: computes based on amount of Thread from Thread Pool usage that are busy servicing requests

As well you also can configure weight (impact of a metric respect to other metrics) and capacity properties;
Below is example, how to change default based on CPU balancing to balancing based on busyness + CPU:

/subsystem=modcluster/mod-cluster-config=configuration/dynamic-load-provider=configuration/load-metric=cpu:remove()
/subsystem=modcluster/mod-cluster-config=configuration:add-metric(type=busyness,weight=2)
/subsystem=modcluster/mod-cluster-config=configuration:add-metric(type=cpu,weight=1)

If predefined types is not enough, - you can provide custom-load-metric by implementing org.jboss.modcluster.load.metric.impl.AbstractLoadMetric. To possibility of using your custom metric,- you need to copy packaged JAR to modcluster module and update module.xml. Now you can use your custom metric with your configuration like

 <custom-load-metric class="org.kostenko.examples.wldfly.modcluster.MyBalancingMetric">