org.apache.beam.sdk.transforms.windowing

Class Repeatedly

java.lang.Object

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

org.apache.beam.sdk.transforms.windowing.Repeatedly

All Implemented Interfaces:

Serializable

public class Repeatedly
extends Trigger

Repeat a trigger, either until some condition is met or forever.

For example, to fire after the end of the window, and every time late data arrives:

 
     Repeatedly.forever(AfterWatermark.isPastEndOfWindow());
  

Repeatedly.forever(someTrigger) behaves like an infinite AfterEach.inOrder(someTrigger, someTrigger, someTrigger, ...).

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

Method Summary

Modifier and Type	Method and Description
static Repeatedly	forever(Trigger repeated) Create a composite trigger that repeatedly executes the trigger repeated, firing each time it fires and ignoring any indications to finish.
Trigger	getContinuationTrigger(List<Trigger> continuationTriggers) Return the Trigger.getContinuationTrigger() of this Trigger.
Instant	getWatermarkThatGuaranteesFiring(BoundedWindow window) Returns a bound in watermark time by which this trigger would have fired at least once for a given window had there been input data.
void	onElement(Trigger.OnElementContext c) Called every time an element is incorporated into a window.
void	onFire(Trigger.TriggerContext context) Adjusts the state of the trigger to be ready for the next pane.
void	onMerge(Trigger.OnMergeContext c) Called immediately after windows have been merged.
boolean	shouldFire(Trigger.TriggerContext context) Returns true if the current state of the trigger indicates that its condition is satisfied and it is ready to fire.
String	toString()

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

clear, equals, getContinuationTrigger, hashCode, isCompatible, orFinally, prefetchOnElement, prefetchOnFire, prefetchOnMerge, prefetchShouldFire, subTriggers

Methods inherited from class java.lang.Object

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

Method Detail

forever

public static Repeatedly forever(Trigger repeated)

Create a composite trigger that repeatedly executes the trigger repeated, firing each time it fires and ignoring any indications to finish.

Unless used with Trigger.orFinally(org.apache.beam.sdk.transforms.windowing.Trigger.OnceTrigger) the composite trigger will never finish.

Parameters:

repeated - the trigger to execute repeatedly.

onElement

public void onElement(Trigger.OnElementContext c)
               throws Exception

Description copied from class: Trigger

Called every time an element is incorporated into a window.

Specified by:

onElement in class Trigger

Throws:

Exception

onMerge

public void onMerge(Trigger.OnMergeContext c)
             throws Exception

Description copied from class: Trigger

Called immediately after windows have been merged.

Leaf triggers should update their state by inspecting their status and any state in the merging windows. Composite triggers should update their state by calling ExecutableTrigger.invokeOnMerge(org.apache.beam.sdk.transforms.windowing.Trigger.OnMergeContext) on their sub-triggers, and applying appropriate logic.

A trigger such as AfterWatermark.pastEndOfWindow() may no longer be finished; it is the responsibility of the trigger itself to record this fact. It is forbidden for a trigger to become finished due to Trigger.onMerge(org.apache.beam.sdk.transforms.windowing.Trigger.OnMergeContext), as it has not yet fired the pending elements that led to it being ready to fire.

The implementation does not need to clear out any state associated with the old windows.

Specified by:

onMerge in class Trigger

Throws:

Exception

getWatermarkThatGuaranteesFiring

public Instant getWatermarkThatGuaranteesFiring(BoundedWindow window)

Description copied from class: Trigger

Returns a bound in watermark time by which this trigger would have fired at least once for a given window had there been input data. This is a static property of a trigger that does not depend on its state.

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

This estimate is used 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

getContinuationTrigger

public Trigger getContinuationTrigger(List<Trigger> continuationTriggers)

Description copied from class: Trigger

Return the Trigger.getContinuationTrigger() of this Trigger. For convenience, this is provided the continuation trigger of each of the sub-triggers.

Specified by:

getContinuationTrigger in class Trigger

shouldFire

public boolean shouldFire(Trigger.TriggerContext context)
                   throws Exception

Description copied from class: Trigger

Returns true if the current state of the trigger indicates that its condition is satisfied and it is ready to fire.

Specified by:

shouldFire in class Trigger

Throws:

Exception

onFire

public void onFire(Trigger.TriggerContext context)
            throws Exception

Description copied from class: Trigger

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

toString

public String toString()

Overrides:

toString in class Trigger