The Java Flight Recorder API contains two annotations TransitionFrom and TransitionTo but the documentation is very light on how they should be used.
How are they supposed to be used? I assume they go on fields of events. Should they be boolean or thread fields? When should the fields be set to which values?
The purpose of @TransitionTo and @TransitionFrom is to hint to a graphical user interface like JDK Mission Control that there is a transition from thread A to thread B.
The GUI can then visualize it as transition arrows:
If you commit the event in thread A, you would create a thread field and annotate it with @TransitionTo and assign thread B to it.
@Name("com.organization.product.Notification")
@Label("Notification")
public class Notification extends jdk.jfr.Event {
@TransitionTo
@Label ("Receiver");
Thread receiver;
}
If it is more convenient to commit the event in thread B, you would create a field annotated with @TransitionFrom and assign it with thread A instead.
@Name("com.organization.product.Notification")
@Label("Notification")
public class Notification extends jdk.jfr.Event {
@TransitionFrom
@Label ("Notifier");
Thread notifier;
}