org.apache.beam.sdk.transforms.windowing

Class DefaultTrigger

java.lang.Object

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

org.apache.beam.sdk.transforms.windowing.DefaultTrigger

All Implemented Interfaces:

java.io.Serializable

@Experimental(value=TRIGGER)
public class DefaultTrigger
extends Trigger

A trigger that is equivalent to Repeatedly.forever(AfterWatermark.pastEndOfWindow()). See Repeatedly.forever(org.apache.beam.sdk.transforms.windowing.Trigger) and AfterWatermark.pastEndOfWindow() for more details.

This is a distinguished class to make it easy for runners to optimize for this common case.

See Also:

Serialized Form

Nested Class Summary

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

Trigger.OnceTrigger

Field Summary

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

subTriggers

Method Summary

Modifier and Type	Method and Description
protected Trigger	getContinuationTrigger(java.util.List<Trigger> continuationTriggers) Subclasses should override this to return the Trigger.getContinuationTrigger() of this Trigger.
Instant	getWatermarkThatGuaranteesFiring(BoundedWindow window) For internal use only; no backwards-compatibility guarantees.
boolean	isCompatible(Trigger other) For internal use only; no backwards-compatibility guarantees.
boolean	mayFinish() For internal use only; no backwards-compatibility guarantees.
static DefaultTrigger	of() Returns the default trigger.

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

equals, getContinuationTrigger, hashCode, orFinally, subTriggers, toString

Methods inherited from class java.lang.Object

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

Method Detail

of

public static DefaultTrigger of()

Returns the default trigger.

getWatermarkThatGuaranteesFiring

public Instant getWatermarkThatGuaranteesFiring(BoundedWindow window)

Description copied from class: Trigger

For internal use only; no backwards-compatibility guarantees.

Returns a bound in event time by which this trigger would have fired at least once for a given window had there been input data.

For triggers that do not fire based on the watermark advancing, returns BoundedWindow.TIMESTAMP_MAX_VALUE.

This estimate may be used, for example, to determine that there are no elements in a side-input window, which causes the default value to be used instead.

Specified by:

getWatermarkThatGuaranteesFiring in class Trigger

mayFinish

public boolean mayFinish()

Description copied from class: Trigger

For internal use only; no backwards-compatibility guarantees.

Indicates whether this trigger may "finish". A top level trigger that finishes can cause data loss, so is rejected by GroupByKey validation.

Specified by:

mayFinish in class Trigger

Returns:

false; the default trigger never finishes

isCompatible

public boolean isCompatible(Trigger other)

Description copied from class: Trigger

For internal use only; no backwards-compatibility guarantees.

Returns whether this performs the same triggering as the given Trigger.

Overrides:

isCompatible in class Trigger

getContinuationTrigger

protected Trigger getContinuationTrigger(java.util.List<Trigger> continuationTriggers)

Description copied from class: Trigger

Subclasses should override this to return the Trigger.getContinuationTrigger() of this Trigger. For convenience, this is provided the continuation trigger of each of the sub-triggers in the same order as Trigger.subTriggers.

Specified by:

getContinuationTrigger in class Trigger

Parameters:

continuationTriggers - null if Trigger.subTriggers is null, otherwise contains the result of Trigger.getContinuationTrigger() on each of the subTriggers in the same order.