What is it?
The Geronimo monitoring plug-in is broken down between server and a client plug-ins, referred to as the 'Agent' and 'Console' respectively. When properly setup, these plug-ins provide both local and remote real time JSR77 compliant statistic monitoring, as well as historical tracking of any exposed statistic with visual representations drawn in the form of graphs through the Dojo Toolkit's dojoX Charting packages.
Agent (Server)
The Agent plug-in can be deployed headless on an instance of Geronimo requiring no administrative console able to be polled by the console plug-in from any instance of Geronimo that can communicate with it. There are two flavors of the Agent plug-in available; the first allowing for EJB connections, and the second allowing for JMX connections between the Console and Agent.
While the EJB Agent is the default plug-in installed with the full JEE5 assembly of Geronimo, the JMX is recommended for those that otherwise would require no form of EJB in their assembly but still require monitoring ability.
Console (Client)
Conversely, the console plug-in, which requires the Geronimo administrative console, can connect to multiple Agent plug-ins across multiple instances of Geronimo, allowing centralized monitoring of statistics on a multitude of machines. The same console is able to connect to either the EJB or the JMX flavor of the Agent plug-in, or even connect to both types on different instances of Geronimo.
What can I monitor?
From within the client plug-in in the administrative console, it is possible to define a connection to any instance of Geronimo that has the monitoring server plug-in deployed. Furthermore, any MBean deployed on the server instance that provides statistics can be historically tracked, allowing for graph generation from any statistic element exactly as defined. Standard behavior of the Monitoring Server is to take snapshots of the JSR77 defined JVM statistics, as well as the web container statistics for the web container being used (either Jetty or Tomcat). Additional MBeans can be added, or these defaults can be easily removed through the Monitoring Console plug-in.