org.apache.beam.sdk.transforms.windowing

Class AfterDelayFromFirstElement

java.lang.Object

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

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

org.apache.beam.sdk.transforms.windowing.AfterDelayFromFirstElement

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

AfterProcessingTime

@Experimental(value=TRIGGER)
public abstract class AfterDelayFromFirstElement
extends Trigger.OnceTrigger

A base class for triggers that happen after a processing time delay from the arrival of the first element in a pane.

This class is for internal use only and may change at any time.

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

Modifier and Type	Field and Description
protected static org.apache.beam.sdk.util.state.StateTag<Object,org.apache.beam.sdk.util.state.AccumulatorCombiningState<Instant,Combine.Holder<Instant>,Instant>>	DELAYED_UNTIL_TAG
protected static List<SerializableFunction<Instant,Instant>>	IDENTITY
protected List<SerializableFunction<Instant,Instant>>	timestampMappers A list of timestampMappers m1, m2, m3, ...

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

subTriggers

Constructor Summary

Constructors

Constructor and Description
AfterDelayFromFirstElement(org.apache.beam.sdk.util.TimeDomain timeDomain, List<SerializableFunction<Instant,Instant>> timestampMappers)

Method Summary

Modifier and Type	Method and Description
AfterDelayFromFirstElement	alignedTo(Duration size) Aligns the time to be the smallest multiple of size greater than the timestamp since the epoch.
AfterDelayFromFirstElement	alignedTo(Duration size, Instant offset) Aligns timestamps to the smallest multiple of size since the offset greater than the timestamp.
void	clear(Trigger.TriggerContext c) Clear any state associated with this trigger in the given window.
protected Instant	computeTargetTimestamp(Instant time)
abstract Instant	getCurrentTime(Trigger.TriggerContext context) To complete an implementation, return the desired time from the TriggerContext.
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.
boolean	isCompatible(Trigger other) Returns whether this performs the same triggering as the given Trigger.
Trigger.OnceTrigger	mappedTo(SerializableFunction<Instant,Instant> timestampMapper) Deprecated. This will be removed in the next major version. Please use only plusDelayOf(org.joda.time.Duration) and alignedTo(org.joda.time.Duration, org.joda.time.Instant).
protected abstract AfterDelayFromFirstElement	newWith(List<SerializableFunction<Instant,Instant>> transform) To complete an implementation, return a new instance like this one, but incorporating the provided timestamp mapping functions.
void	onElement(Trigger.OnElementContext c) Called every time an element is incorporated into a window.
void	onMerge(Trigger.OnMergeContext c) Called immediately after windows have been merged.
protected void	onOnlyFiring(Trigger.TriggerContext context) Called exactly once by Trigger.OnceTrigger.onFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) when the trigger is fired.
AfterDelayFromFirstElement	plusDelayOf(Duration delay) Adds some delay to the original target time.
void	prefetchOnElement(org.apache.beam.sdk.util.state.StateAccessor<?> state) Called to allow the trigger to prefetch any state it will likely need to read from during an Trigger.onElement(org.apache.beam.sdk.transforms.windowing.Trigger.OnElementContext) call.
void	prefetchOnMerge(org.apache.beam.sdk.util.state.MergingStateAccessor<?,?> state) Called to allow the trigger to prefetch any state it will likely need to read from during an Trigger.onMerge(org.apache.beam.sdk.transforms.windowing.Trigger.OnMergeContext) call.
void	prefetchShouldFire(org.apache.beam.sdk.util.state.StateAccessor<?> state) Called to allow the trigger to prefetch any state it will likely need to read from during an Trigger.shouldFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) call.
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.

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

getContinuationTrigger, onFire

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

equals, getContinuationTrigger, hashCode, orFinally, prefetchOnFire, subTriggers, toString

Methods inherited from class java.lang.Object

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

Field Detail

IDENTITY

protected static final List<SerializableFunction<Instant,Instant>> IDENTITY

DELAYED_UNTIL_TAG

protected static final org.apache.beam.sdk.util.state.StateTag<Object,org.apache.beam.sdk.util.state.AccumulatorCombiningState<Instant,Combine.Holder<Instant>,Instant>> DELAYED_UNTIL_TAG

timestampMappers

protected final List<SerializableFunction<Instant,Instant>> timestampMappers

A list of timestampMappers m1, m2, m3, ... m_n considered to be composed in sequence. The overall mapping for an instance `instance` is `m_n(... m3(m2(m1(instant))`, implemented via #computeTargetTimestamp

Constructor Detail

AfterDelayFromFirstElement

public AfterDelayFromFirstElement(org.apache.beam.sdk.util.TimeDomain timeDomain,
                                  List<SerializableFunction<Instant,Instant>> timestampMappers)

Method Detail

getCurrentTime

@Nullable
public abstract Instant getCurrentTime(Trigger.TriggerContext context)

To complete an implementation, return the desired time from the TriggerContext.

newWith

protected abstract AfterDelayFromFirstElement newWith(List<SerializableFunction<Instant,Instant>> transform)

To complete an implementation, return a new instance like this one, but incorporating the provided timestamp mapping functions. Generally should be used by calling the constructor of this class from the constructor of the subclass.

alignedTo

public AfterDelayFromFirstElement alignedTo(Duration size,
                                            Instant offset)

Aligns timestamps to the smallest multiple of size since the offset greater than the timestamp.

TODO: Consider sharing this with FixedWindows, and bring over the equivalent of CalendarWindows.

alignedTo

public AfterDelayFromFirstElement alignedTo(Duration size)

Aligns the time to be the smallest multiple of size greater than the timestamp since the epoch.

plusDelayOf

public AfterDelayFromFirstElement plusDelayOf(Duration delay)

Adds some delay to the original target time.

Parameters:

delay - the delay to add

Returns:

An updated time trigger that will wait the additional time before firing.

mappedTo

@Deprecated
public Trigger.OnceTrigger mappedTo(SerializableFunction<Instant,Instant> timestampMapper)

Deprecated. This will be removed in the next major version. Please use only plusDelayOf(org.joda.time.Duration) and alignedTo(org.joda.time.Duration, org.joda.time.Instant).

isCompatible

public boolean isCompatible(Trigger other)

Description copied from class: Trigger

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

Overrides:

isCompatible in class Trigger

prefetchOnElement

public void prefetchOnElement(org.apache.beam.sdk.util.state.StateAccessor<?> state)

Description copied from class: Trigger

Called to allow the trigger to prefetch any state it will likely need to read from during an Trigger.onElement(org.apache.beam.sdk.transforms.windowing.Trigger.OnElementContext) call.

Overrides:

prefetchOnElement in class Trigger

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

prefetchOnMerge

public void prefetchOnMerge(org.apache.beam.sdk.util.state.MergingStateAccessor<?,?> state)

Description copied from class: Trigger

Called to allow the trigger to prefetch any state it will likely need to read from during an Trigger.onMerge(org.apache.beam.sdk.transforms.windowing.Trigger.OnMergeContext) call.

Overrides:

prefetchOnMerge in class Trigger

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

prefetchShouldFire

public void prefetchShouldFire(org.apache.beam.sdk.util.state.StateAccessor<?> state)

Description copied from class: Trigger

Called to allow the trigger to prefetch any state it will likely need to read from during an Trigger.shouldFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) call.

Overrides:

prefetchShouldFire in class Trigger

clear

public void clear(Trigger.TriggerContext c)
           throws Exception

Description copied from class: Trigger

Clear any state associated with this trigger in the given window.

This is called after a trigger has indicated it will never fire again. The trigger system keeps enough information to know that the trigger is finished, so this trigger should clear all of its state.

Overrides:

clear 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

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

onOnlyFiring

protected void onOnlyFiring(Trigger.TriggerContext context)
                     throws Exception

Description copied from class: Trigger.OnceTrigger

Called exactly once by Trigger.OnceTrigger.onFire(org.apache.beam.sdk.transforms.windowing.Trigger.TriggerContext) when the trigger is fired. By default, invokes Trigger.OnceTrigger.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.

Specified by:

onOnlyFiring in class Trigger.OnceTrigger

Throws:

Exception

computeTargetTimestamp

protected Instant computeTargetTimestamp(Instant time)