When alert-threshold function is activated in gateway senders (set alert-threshold to non zero value),
event is never raised, for entries which are in queue longer than alert-threshold value.
Printout from logs:
Monitor = GatewaySenderMXBeanMonitor descriptor = eventsExceedingAlertThreshold And value = 0
It seams that reporting of events which exceed alert threshold (class AbstractGatewaySenderEventProcessor), is working only if dispatcher is instance of GatewaySenderEventCallbackDispatcher.
With deeper analysis, I got to conclusion that for GatewaySender - dispatcher is instance of GatewaySenderEventRemoteDispatcher.
So this function is only working for AsyncEventQueue, for which dispatcher is instance of GatewaySenderEventCallbackDispatcher.
The other problem is that getEventsExceedingAlertThreshold() method of GatewaySenderMBean is always returning hardcoded value (0).