How to configure the interval of a custom JFR event

Question

I am implementing a custom JFR event that samples a counter at a certain interval. It would be awesome if this event and interval could be configured in a .jfc configuration file like the built-in events. For that to work I need programmatic access to the configured value. Through EventFactory if have access to the SettingDescriptor but this gives me only the default value, not the current value.

I had a look at jdk.jfr.internal.settings.PeriodSetting but this is an internal class.

Answer 1

Custom events can be configured in a .jfc file.

<event name="Foo">
  <setting name="enabled">true</setting>
  <setting name="period">5 s</setting>
</event>

or programmatically with a Map:

 Recording r = new Recording();
 Map<String, String> settings = new HashMap<>();
 settings.put("Foo#enabled", "true");
 settings.put("Foo#period", "5 s");
 r.setSettings(settings);
 r.start();

or using fluent API:

 r.enable("Foo").withPeriod(Duration.ofSeconds(5));

The time when events are emitted is determined by the framework:

FlightRecorder.addPeriodicEvent(Foo.class, ()-> {
  Foo foo = new Foo();
  foo.bar = Sampler.sample();
  foo.commit();
});

If the field layout of the event is unknown at compile time, so you have to use the EventFactory, you can do:

  final EventFactory factory = ...
  Event event = factory.newEvent();
  Class<Event> eventClass = event.getClass();
  FlightRecorder.addPeriodicEvent(eventClass, ()-> {
    Event foo = factory.newEvent();
    foo.set(0, Sampler.sample());
    foo.commit();
  });