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

Class CountEvictionPolicy<IN>

java.lang.Object

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

Type Parameters:

IN - the type of the incoming data points

All Implemented Interfaces:

Serializable, Cloneable, CloneableEvictionPolicy<IN>, EvictionPolicy<IN>

public class CountEvictionPolicy<IN>
extends Object
implements CloneableEvictionPolicy<IN>

This eviction policy allows the eviction of data points from the buffer using a counter of arriving elements and a threshold (maximal buffer size) By default this policy does not react on fake elements. Wrap it in an ActiveEvictionPolicyWrapper to make it count even fake elements.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
CountEvictionPolicy(int maxElements) This constructor allows the setup of the simplest possible count based eviction.
CountEvictionPolicy(int maxElements, int deleteOnEviction) This constructor allows to set up both, the maximum number of elements and the number of elements to be deleted in case of an eviction.
CountEvictionPolicy(int maxElements, int deleteOnEviction, int startValue) The same as CountEvictionPolicy(int, int).

Method Summary

Modifier and Type	Method and Description
CountEvictionPolicy<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	getDeleteOnEviction()
int	getStart()
int	getWindowSize()
int	notifyEviction(IN datapoint, boolean triggered, int bufferSize) Proves if and how many elements should be deleted from the element buffer.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

CountEvictionPolicy

public CountEvictionPolicy(int maxElements)

This constructor allows the setup of the simplest possible count based eviction. It keeps the size of the buffer according to the given maxElements parameter by deleting the oldest element in the buffer. Eviction only takes place if the counter of arriving elements would be higher than maxElements without eviction.

Parameters:

maxElements - The maximum number of elements before eviction. As soon as one more element arrives, the oldest element will be deleted

CountEvictionPolicy

public CountEvictionPolicy(int maxElements,
                           int deleteOnEviction)

This constructor allows to set up both, the maximum number of elements and the number of elements to be deleted in case of an eviction. Eviction only takes place if the counter of arriving elements would be higher than maxElements without eviction. In such a case deleteOnEviction elements will be removed from the buffer. The counter of arriving elements is adjusted respectively, but never set below zero: counter=(counter-deleteOnEviction<0)?0:counter-deleteOnEviction

Parameters:

maxElements - maxElements The maximum number of elements before eviction.

deleteOnEviction - The number of elements to be deleted on eviction. The counter will be adjusted respectively but never below zero.

CountEvictionPolicy

public CountEvictionPolicy(int maxElements,
                           int deleteOnEviction,
                           int startValue)

The same as CountEvictionPolicy(int, int). Additionally a custom start value for the counter of arriving elements can be set. By setting a negative start value the first eviction can be delayed.

Parameters:

maxElements - maxElements The maximum number of elements before eviction.

deleteOnEviction - The number of elements to be deleted on eviction. The counter will be adjusted respectively but never below zero.

startValue - A custom start value for the counter of arriving elements.

See Also:

CountEvictionPolicy(int, int)

Method Detail

notifyEviction

public int notifyEviction(IN 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<IN>

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 CountEvictionPolicy<IN> clone()

Description copied from interface: CloneableEvictionPolicy

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

Specified by:

clone in interface CloneableEvictionPolicy<IN>

Overrides:

clone in class Object

Returns:

a copy of this object

equals

public boolean equals(Object other)

Overrides:

equals in class Object

getWindowSize

public int getWindowSize()

getStart

public int getStart()

getDeleteOnEviction

public int getDeleteOnEviction()

toString

public String toString()

Overrides:

toString in class Object