org.apache.flink.streaming.api.windowing.policy

Class CountTriggerPolicy<IN>

java.lang.Object

org.apache.flink.streaming.api.windowing.policy.CountTriggerPolicy<IN>

Type Parameters:

IN - The type of the data points which are handled by this policy

All Implemented Interfaces:

Serializable, Cloneable, CloneableTriggerPolicy<IN>, TriggerPolicy<IN>

public class CountTriggerPolicy<IN>
extends Object
implements CloneableTriggerPolicy<IN>

This policy triggers at every n'th element.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_START_VALUE

Constructor Summary

Constructors

Constructor and Description
CountTriggerPolicy(int max) This constructor will set up a count based trigger, which triggers after max elements have arrived.
CountTriggerPolicy(int max, int startValue) In addition to CountTriggerPolicy(int) this constructor allows to set a custom start value for the element counter.

Method Summary

Modifier and Type	Method and Description
CountTriggerPolicy<IN>	clone() This method should return an exact copy of the object it belongs to including the current object state.
boolean	equals(Object other)
int	getSlideSize()
int	getStart()
boolean	notifyTrigger(IN datapoint) Proves and returns if a new window should be started.
String	toString()

Methods inherited from class java.lang.Object

finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_START_VALUE

public static final int DEFAULT_START_VALUE

See Also:

Constant Field Values

Constructor Detail

CountTriggerPolicy

public CountTriggerPolicy(int max)

This constructor will set up a count based trigger, which triggers after max elements have arrived.

Parameters:

max - The number of arriving elements before the trigger occurs.

CountTriggerPolicy

public CountTriggerPolicy(int max,
                          int startValue)

In addition to CountTriggerPolicy(int) this constructor allows to set a custom start value for the element counter. This can be used to delay the first trigger by setting a negative start value. Often the first trigger should be delayed in case of sliding windows. For example if the size of a window should be 4 and a trigger should happen every 2, a start value of -2 would allow to also have the first window of size 4.

Parameters:

max - The number of arriving elements before the trigger occurs.

startValue - The start value for the counter of arriving elements.

See Also:

CountTriggerPolicy(int)

Method Detail

notifyTrigger

public boolean notifyTrigger(IN datapoint)

Description copied from interface: TriggerPolicy

Proves and returns if a new window should be started. In case the trigger occurs (return value true) the UDF will be executed on the current element buffer without the last added element which is provided as parameter. This element will be added to the buffer after the execution of the UDF. There are possibly different strategies for eviction and triggering: 1) including last data point: Better/faster for count eviction 2) excluding last data point: Essentially required for time based eviction and delta rules As 2) is required for some policies and the benefit of using 1) is small for the others, policies are implemented according to 2).

Specified by:

notifyTrigger in interface TriggerPolicy<IN>

Parameters:

datapoint - the data point which arrived

Returns:

true if the current windows should be closed, otherwise false. In true case the given data point will be part of the next window and will not be included in the current one.

clone

public CountTriggerPolicy<IN> clone()

Description copied from interface: CloneableTriggerPolicy

This method should return an exact copy of the object it belongs to including the current object state.

Specified by:

clone in interface CloneableTriggerPolicy<IN>

Overrides:

clone in class Object

Returns:

a copy of this object

equals

public boolean equals(Object other)

Overrides:

equals in class Object

getSlideSize

public int getSlideSize()

getStart

public int getStart()

toString

public String toString()

Overrides:

toString in class Object