Composite triggers

A composite trigger in Apache Beam allows you to specify multiple triggers to be used in combination. When any of the triggers fire, the composite trigger will fire. This allows you to combine different types of triggers to create more complex triggering strategies.

{{if (eq .Sdk “go”)}}

trigger := trigger.AfterAll([]trigger.Trigger{trigger.AfterEndOfWindow().
	EarlyFiring(trigger.AfterProcessingTime().
		PlusDelay(60 * time.Second)).
	LateFiring(trigger.Repeat(trigger.AfterCount(1))),trigger.AfterCount(2)})

{{end}} {{if (eq .Sdk “java”)}}

Window<String> window = Window.into(FixedWindows.of(Duration.standardMinutes(5)));

Trigger processingTimeTrigger = AfterProcessingTime.pastFirstElementInPane().plusDelayOf(Duration.standardMinutes(1));
Trigger dataDrivenTrigger = AfterPane.elementCountAtLeast(2);

PCollection<String> windowed = input.apply(window.triggering(AfterAll.of(Arrays.asList(processingTimeTrigger,dataDrivenTrigger))).withAllowedLateness(Duration.ZERO).accumulatingFiredPanes());

{{end}} {{if (eq .Sdk “python”)}}

processing_time_trigger = trigger.AfterProcessingTime(60)
event_time_trigger = trigger.AfterWatermark(early=trigger.AfterCount(100),
                                             late=trigger.AfterCount(200))

composite_trigger = trigger.AfterAll(processing_time_trigger,event_time_trigger)

{{end}}

Playground exercise

In composite triggers, you can make sure that after the first trigger is triggered, the second trigger is triggered

{{if (eq .Sdk “go”)}}

{{end}}

{{if (eq .Sdk “java”)}}

Trigger trigger = AfterFirst.of(
    AfterCount.of(100),
    AfterProcessingTime.pastFirstElementInPane().plusDelayOf(Duration.standardMinutes(5))
);

{{end}} {{if (eq .Sdk “python”)}}

input | 'WindowIntoFixedWindows' >> beam.WindowInto(beam.window.FixedWindows(10))
      | 'CountAndProcessTimeTrigger' >> beam.Trigger(
            AfterFirst.of(
                AfterCount(100),
                AfterProcessingTime(5*60)  # 5 minutes
            )
      )

{{end}}