The org.zkoss.zk.ui.util.ExecutionMonitor interface
From Documentation
Listener:
org.zkoss.zk.ui.util.ExecutionMonitor
An application-level listener to monitor executions on activation, deactivation, or waiting for activation. It can also monitors event processing , enabling it to gather information on the event processing order and performance, while PerformanceMeter can be used to monitors the AU requests.
A listener could implement ExecutionMonitor to monitor executions.
Instantiation: Please note that a single listener is used for the whole application. It should be thread-safe and efficient to avoid reducing general performance. In addition, it shouldn't throw any exception, and shouldn't hold a reference to executions. If references to desktops are held, they should be cleaned up when desktopDestroy(org.zkoss.zk.ui.Desktop) is called.