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

Class CountTrigger<W extends Window>

java.lang.Object

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

org.apache.flink.streaming.api.windowing.triggers.CountTrigger<W>

Type Parameters:

W - The type of Windows on which this trigger can operate.

All Implemented Interfaces:

Serializable

@PublicEvolving
public class CountTrigger<W extends Window>
extends Trigger<Object,W>

A Trigger that fires once the count of elements in a pane reaches the given count.

See Also:

• 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	Description
boolean	canMerge()	Returns true if this trigger supports merging of trigger state and can therefore be used with a MergingWindowAssigner.
void	clear(W window, Trigger.TriggerContext ctx)	Clears any state that the trigger might still hold for the given window.
long	getMaxCount()
static <W extends Window> CountTrigger<W>	of(long maxCount)	Creates a trigger that fires once the number of elements in a pane reaches the given count.
TriggerResult	onElement(Object element, long timestamp, W window, Trigger.TriggerContext ctx)	Called for every element that gets added to a pane.
TriggerResult	onEventTime(long time, W window, Trigger.TriggerContext ctx)	Called when an event-time timer that was set using the trigger context fires.
void	onMerge(W window, Trigger.OnMergeContext ctx)	Called when several windows have been merged into one window by the WindowAssigner.
TriggerResult	onProcessingTime(long time, W 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 Details

onElement

public TriggerResult onElement(Object element,
 long timestamp,
 W 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,W extends Window>

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,
 W window,
 Trigger.TriggerContext ctx)

Description copied from class: Trigger

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

Specified by:

onEventTime in class Trigger<Object,W extends Window>

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,
 W 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.

Specified by:

onProcessingTime in class Trigger<Object,W extends Window>

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(W 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,W extends Window>

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,W extends Window>

onMerge

public void onMerge(W window,
 Trigger.OnMergeContext ctx)
             throws Exception

Description copied from class: Trigger

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

Overrides:

onMerge in class Trigger<Object,W extends Window>

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.

Throws:

Exception

toString

public String toString()

Overrides:

toString in class Object

getMaxCount

public long getMaxCount()

of

public static <W extends Window> CountTrigger<W> of(long maxCount)

Creates a trigger that fires once the number of elements in a pane reaches the given count.

Type Parameters:

W - The type of Windows on which this trigger can operate.

Parameters:

maxCount - The count of elements at which to fire.