org.apache.storm.windowing

Class WatermarkTimeEvictionPolicy<T>

java.lang.Object

org.apache.storm.windowing.TimeEvictionPolicy<T>

org.apache.storm.windowing.WatermarkTimeEvictionPolicy<T>

All Implemented Interfaces:

EvictionPolicy<T>

public class WatermarkTimeEvictionPolicy<T>
extends TimeEvictionPolicy<T>

An eviction policy that evicts events based on time duration taking watermark time and event lag into account.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.storm.windowing.EvictionPolicy

EvictionPolicy.Action

Field Summary

Fields inherited from class org.apache.storm.windowing.TimeEvictionPolicy

evictionContext, referenceTime

Constructor Summary

Constructors

Constructor and Description
WatermarkTimeEvictionPolicy(int windowLength) Constructs a WatermarkTimeEvictionPolicy that evicts events older than the given window length in millis.
WatermarkTimeEvictionPolicy(int windowLength, int lag) Constructs a WatermarkTimeEvictionPolicy that evicts events older than the given window length in millis.

Method Summary

Modifier and Type	Method and Description
EvictionPolicy.Action	evict(org.apache.storm.windowing.Event<T> event) Decides if an event should be expired from the window, processed in the current window or kept for later processing.
String	toString()

Methods inherited from class org.apache.storm.windowing.TimeEvictionPolicy

setContext, track

Methods inherited from class java.lang.Object

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

Constructor Detail

WatermarkTimeEvictionPolicy

public WatermarkTimeEvictionPolicy(int windowLength)

Constructs a WatermarkTimeEvictionPolicy that evicts events older than the given window length in millis.

Parameters:

windowLength - the window length in milliseconds

WatermarkTimeEvictionPolicy

public WatermarkTimeEvictionPolicy(int windowLength,
                                   int lag)

Constructs a WatermarkTimeEvictionPolicy that evicts events older than the given window length in millis. The lag parameter can be used in the case of event based ts to break the queue scan early.

Parameters:

windowLength - the window length in milliseconds

lag - the max event lag in milliseconds

Method Detail

evict

public EvictionPolicy.Action evict(org.apache.storm.windowing.Event<T> event)

Decides if an event should be expired from the window, processed in the current window or kept for later processing.

Keeps events with future ts in the queue for processing in the next window. If the ts difference is more than the lag, stops scanning the queue for the current window.

Specified by:

evict in interface EvictionPolicy<T>

Overrides:

evict in class TimeEvictionPolicy<T>

Parameters:

event - the input event

Returns:

the EvictionPolicy.Action to be taken based on the input event

toString

public String toString()

Overrides:

toString in class TimeEvictionPolicy<T>