JMX

JMX support is disabled by default.

To enable JMX support, set the log4j2.disableJmx system property when starting the Java VM:

log4j2.disableJmx=false

To perform local monitoring you need to set the log4j2.disableJmx system property to false. The JConsole tool that is included in the Java JDK can be used to monitor your application. Start JConsole by typing $JAVA_HOME/bin/jconsole in a command shell. For more details, see Oracle’s documentation at how to use JConsole.

To enable monitoring and management from remote systems, set the following two system properties when starting the Java VM:

log4j2.disableJmx=false

and

com.sun.management.jmxremote.port=portNum

In the property above, portNum is the port number through which you want to enable JMX RMI connections.

For more details, see Oracle’s documentation at Remote Monitoring and Management.

Be aware that RMI by default triggers a full GC every hour. See the Oracle documentation for the sun.rmi.dgc.server.gcInterval and sun.rmi.dgc.client.gcInterval properties. The default value of both properties is 3600000 milliseconds (one hour). Before Java 6, it was one minute.

The two sun.rmi arguments reflect whether your JVM is running in server or client mode. If you want to modify the GC interval time it may be best to specify both properties to ensure the argument is picked up by the JVM.

An alternative may be to disable explicit calls to System.gc() altogether with -XX:+DisableExplicitGC, or (if you are using the CMS or G1 collector) add -XX:+ExplicitGCInvokesConcurrent to ensure the full GCs are done concurrently in parallel with your application instead of forcing a stop-the-world collection.

The best way to find out which methods and attributes of the various Log4j components are accessible via JMX is to look at the org.apache.logging.log4j.core.jmx package contents in the log4j-core artifact or by exploring directly in JConsole.

The screenshot below shows the Log4j MBeans in JConsole.

The Apache Log4j JMX GUI is a basic client GUI that can be used to monitor the StatusLogger output and to remotely modify the Log4j configuration. The client GUI can be run as a stand-alone application or as a JConsole plug-in.