org.apache.beam.sdk.transforms.windowing

Class Trigger.OnceTrigger

java.lang.Object

org.apache.beam.sdk.transforms.windowing.Trigger

org.apache.beam.sdk.transforms.windowing.Trigger.OnceTrigger

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

AfterAll, AfterDelayFromFirstElement, AfterFirst, AfterPane, AfterWatermark.FromEndOfWindow

Enclosing class:

Trigger

public abstract static class Trigger.OnceTrigger
extends Trigger

Triggers that are guaranteed to fire at most once should extend from this, rather than the general Trigger class to indicate that behavior.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.beam.sdk.transforms.windowing.Trigger

Trigger.MergingTriggerInfo, Trigger.OnceTrigger, Trigger.OnElementContext, Trigger.OnMergeContext, Trigger.TriggerContext, Trigger.TriggerInfo

Field Summary

Fields inherited from class org.apache.beam.sdk.transforms.windowing.Trigger

subTriggers

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	OnceTrigger(List<Trigger> subTriggers)

Method Summary

Modifier and Type	Method and Description
Trigger.OnceTrigger	getContinuationTrigger() Return a trigger to use after a GroupByKey to preserve the intention of this trigger.
void	onFire(Trigger.TriggerContext context) Adjusts the state of the trigger to be ready for the next pane.
protected abstract void	onOnlyFiring(Trigger.TriggerContext context) Called exactly once by onFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) when the trigger is fired.

Methods inherited from class org.apache.beam.sdk.transforms.windowing.Trigger

clear, equals, getContinuationTrigger, getWatermarkThatGuaranteesFiring, hashCode, isCompatible, onElement, onMerge, orFinally, prefetchOnElement, prefetchOnFire, prefetchOnMerge, prefetchShouldFire, shouldFire, subTriggers, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

OnceTrigger

protected OnceTrigger(List<Trigger> subTriggers)

Method Detail

getContinuationTrigger

public final Trigger.OnceTrigger getContinuationTrigger()

Description copied from class: Trigger

Return a trigger to use after a GroupByKey to preserve the intention of this trigger. Specifically, triggers that are time based and intended to provide speculative results should continue providing speculative results. Triggers that fire once (or multiple times) should continue firing once (or multiple times).

Overrides:

getContinuationTrigger in class Trigger

onFire

public final void onFire(Trigger.TriggerContext context)
                  throws Exception

Adjusts the state of the trigger to be ready for the next pane. For example, a Repeatedly trigger will reset its inner trigger, since it has fired.

If the trigger is finished, it is the responsibility of the trigger itself to record that fact via the context.

Specified by:

onFire in class Trigger

Throws:

Exception

onOnlyFiring

protected abstract void onOnlyFiring(Trigger.TriggerContext context)
                              throws Exception

Called exactly once by onFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) when the trigger is fired. By default, invokes onFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) on all subtriggers for which Trigger.shouldFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) is true.

Throws:

Exception