org.apache.flink.streaming.api.windowing.triggers

Class EventTimeTrigger

java.lang.Object

org.apache.flink.streaming.api.windowing.triggers.Trigger<Object,TimeWindow>

org.apache.flink.streaming.api.windowing.triggers.EventTimeTrigger

All Implemented Interfaces:

Serializable

@PublicEvolving
public class EventTimeTrigger
extends Trigger<Object,TimeWindow>

A Trigger that fires once the watermark passes the end of the window to which a pane belongs.

See Also:

Watermark, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.flink.streaming.api.windowing.triggers.Trigger

Trigger.OnMergeContext, Trigger.TriggerContext

Method Summary

Modifier and Type	Method and Description
boolean	canMerge() Returns true if this trigger supports merging of trigger state and can therefore be used with a MergingWindowAssigner.
void	clear(TimeWindow window, Trigger.TriggerContext ctx) Clears any state that the trigger might still hold for the given window.
static EventTimeTrigger	create() Creates an event-time trigger that fires once the watermark passes the end of the window.
TriggerResult	onElement(Object element, long timestamp, TimeWindow window, Trigger.TriggerContext ctx) Called for every element that gets added to a pane.
TriggerResult	onEventTime(long time, TimeWindow window, Trigger.TriggerContext ctx) Called when an event-time timer that was set using the trigger context fires.
void	onMerge(TimeWindow window, Trigger.OnMergeContext ctx) Called when several windows have been merged into one window by the WindowAssigner.
TriggerResult	onProcessingTime(long time, TimeWindow window, Trigger.TriggerContext ctx) Called when a processing-time timer that was set using the trigger context fires.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

onElement

public TriggerResult onElement(Object element,
                               long timestamp,
                               TimeWindow window,
                               Trigger.TriggerContext ctx)
                        throws Exception

Description copied from class: Trigger

Called for every element that gets added to a pane. The result of this will determine whether the pane is evaluated to emit results.

Specified by:

onElement in class Trigger<Object,TimeWindow>

Parameters:

element - The element that arrived.

timestamp - The timestamp of the element that arrived.

window - The window to which the element is being added.

ctx - A context object that can be used to register timer callbacks.

Throws:

Exception

onEventTime

public TriggerResult onEventTime(long time,
                                 TimeWindow window,
                                 Trigger.TriggerContext ctx)

Description copied from class: Trigger

Called when an event-time timer that was set using the trigger context fires.

Note: This method is not called in case the window does not contain any elements. Thus, if you return PURGE from a trigger method and you expect to do cleanup in a future invocation of a timer callback it might be wise to clean any state that you would clean in the timer callback.

Specified by:

onEventTime in class Trigger<Object,TimeWindow>

Parameters:

time - The timestamp at which the timer fired.

window - The window for which the timer fired.

ctx - A context object that can be used to register timer callbacks.

onProcessingTime

public TriggerResult onProcessingTime(long time,
                                      TimeWindow window,
                                      Trigger.TriggerContext ctx)
                               throws Exception

Description copied from class: Trigger

Called when a processing-time timer that was set using the trigger context fires.

Note: This method is not called in case the window does not contain any elements. Thus, if you return PURGE from a trigger method and you expect to do cleanup in a future invocation of a timer callback it might be wise to clean any state that you would clean in the timer callback.

Specified by:

onProcessingTime in class Trigger<Object,TimeWindow>

Parameters:

time - The timestamp at which the timer fired.

window - The window for which the timer fired.

ctx - A context object that can be used to register timer callbacks.

Throws:

Exception

clear

public void clear(TimeWindow window,
                  Trigger.TriggerContext ctx)
           throws Exception

Description copied from class: Trigger

Clears any state that the trigger might still hold for the given window. This is called when a window is purged. Timers set using Trigger.TriggerContext.registerEventTimeTimer(long) and Trigger.TriggerContext.registerProcessingTimeTimer(long) should be deleted here as well as state acquired using Trigger.TriggerContext.getPartitionedState(StateDescriptor).

Specified by:

clear in class Trigger<Object,TimeWindow>

Throws:

Exception

canMerge

public boolean canMerge()

Description copied from class: Trigger

Returns true if this trigger supports merging of trigger state and can therefore be used with a MergingWindowAssigner.

If this returns true you must properly implement Trigger.onMerge(Window, OnMergeContext)

Overrides:

canMerge in class Trigger<Object,TimeWindow>

onMerge

public void onMerge(TimeWindow window,
                    Trigger.OnMergeContext ctx)

Description copied from class: Trigger

Called when several windows have been merged into one window by the WindowAssigner.

Overrides:

onMerge in class Trigger<Object,TimeWindow>

Parameters:

window - The new window that results from the merge.

ctx - A context object that can be used to register timer callbacks and access state.

toString

public String toString()

Overrides:

toString in class Object

create

public static EventTimeTrigger create()

Creates an event-time trigger that fires once the watermark passes the end of the window.

Once the trigger fires all elements are discarded. Elements that arrive late immediately trigger window evaluation with just this one element.