A subsystem monitor is an object that monitors the health of a remote system. It uses an event source to inform all registered listeners of the health of the system.
Advanced Java 2 Platform Enterprise Edition (J2EE) applications often rely on remote, non-managed, non-J2EE systems. These remote systems can periodically send clients a message to indicate that they are working. A subsystem monitor is a set of alarms that tracks indicator messages or heart beats from a remote system.
Make the Missed heart beats until dead value greater or equal to the Missed heart beats until stale value. If Missed heart beats until stale value equals the Missed heart beats until dead value, then a stale event is not published. Only a dead event is published.
You can register a listener that implements the SubsystemMonitorEvents interface for applications that require notification of events. For more information on the SybsystemMonitorEvents interface, see the API documentation.
Heart beat messages can be transmitted using a variety of mechanisms. The application must call the SubsystemMonitor ping() method whenever a heart beat message arrives from a remote system, but the method used to detect these messages is up to the application. For example, you might use a Java Message Service (JMS) publish or subscribe implementation or even a third-party Java messaging product that does not implement JMS.