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

Class DeltaPolicy<DATA>

java.lang.Object

org.apache.flink.streaming.api.windowing.policy.DeltaPolicy<DATA>

Type Parameters:

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

All Implemented Interfaces:

Serializable, Cloneable, CloneableEvictionPolicy<DATA>, CloneableTriggerPolicy<DATA>, EvictionPolicy<DATA>, TriggerPolicy<DATA>

public class DeltaPolicy<DATA>
extends Object
implements CloneableTriggerPolicy<DATA>, CloneableEvictionPolicy<DATA>

This policy calculates a delta between the data point which triggered last and the currently arrived data point. It triggers if the delta is higher than a specified threshold. In case it gets used for eviction, this policy starts from the first element of the buffer and removes all elements from the buffer which have a higher delta then the threshold. As soon as there is an element with a lower delta, the eviction stops. By default this policy does not react on fake elements. Wrap it in an ActiveEvictionPolicyWrapper to make it calculate the delta even on fake elements.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected DeltaFunction<DATA>	deltaFuntion
protected double	threshold
protected DATA	triggerDataPoint

Constructor Summary

Constructors

Constructor and Description
DeltaPolicy(DeltaFunction<DATA> deltaFuntion, DATA init, double threshold, org.apache.flink.api.common.typeutils.TypeSerializer typeSerializer) Creates a delta policy which calculates a delta between the data point which triggered last and the currently arrived data point.

Method Summary

Modifier and Type	Method and Description
DeltaPolicy<DATA>	clone() This method should return an exact copy of the object it belongs to including the current object state.
boolean	equals(Object other)
int	notifyEviction(DATA datapoint, boolean triggered, int bufferSize) Proves if and how many elements should be deleted from the element buffer.
boolean	notifyTrigger(DATA 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

deltaFuntion

protected DeltaFunction<DATA> deltaFuntion

threshold

protected double threshold

triggerDataPoint

protected transient DATA triggerDataPoint

Constructor Detail

DeltaPolicy

public DeltaPolicy(DeltaFunction<DATA> deltaFuntion,
                   DATA init,
                   double threshold,
                   org.apache.flink.api.common.typeutils.TypeSerializer typeSerializer)

Creates a delta policy which calculates a delta between the data point which triggered last and the currently arrived data point. It triggers if the delta is higher than a specified threshold. As the data may be sent to the cluster a TypeSerializer is needed for the initial value.

In case it gets used for eviction, this policy starts from the first element of the buffer and removes all elements from the buffer which have a higher delta then the threshold. As soon as there is an element with a lower delta, the eviction stops.

Parameters:

deltaFuntion - The delta function to be used.

init - The initial to be used for the calculation of a delta before the first trigger.

threshold - The threshold upon which a triggering should happen.

typeSerializer - TypeSerializer to properly forward the initial value to the cluster

Method Detail

notifyTrigger

public boolean notifyTrigger(DATA 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<DATA>

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.

notifyEviction

public int notifyEviction(DATA datapoint,
                          boolean triggered,
                          int bufferSize)

Description copied from interface: EvictionPolicy

Proves if and how many elements should be deleted from the element buffer. The eviction takes place after the trigger and after the call to the UDF but before the adding of the new data point.

Specified by:

notifyEviction in interface EvictionPolicy<DATA>

Parameters:

datapoint - data point the data point which arrived

triggered - Information whether the UDF was triggered or not

bufferSize - The current size of the element buffer at the operator

Returns:

The number of elements to be deleted from the buffer

clone

public DeltaPolicy<DATA> 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 CloneableEvictionPolicy<DATA>

Specified by:

clone in interface CloneableTriggerPolicy<DATA>

Overrides:

clone in class Object

Returns:

a copy of this object

equals

public boolean equals(Object other)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object