org.apache.pulsar.functions.windowing.evictors.WatermarkTimeEvictionPolicy Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
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* specific language governing permissions and limitations
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*/
package org.apache.pulsar.functions.windowing.evictors;
import org.apache.pulsar.functions.windowing.Event;
/**
* An eviction policy that evicts events based on time duration taking
* watermark time and event lag into account.
*/
public class WatermarkTimeEvictionPolicy extends TimeEvictionPolicy {
private final long lag;
/**
* Constructs a WatermarkTimeEvictionPolicy that evicts events older
* than the given window length in millis.
*
* @param windowLength the window length in milliseconds
*/
public WatermarkTimeEvictionPolicy(long windowLength) {
this(windowLength, Long.MAX_VALUE);
}
/**
* 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.
*
* @param windowLength the window length in milliseconds
* @param lag the max event lag in milliseconds
*/
public WatermarkTimeEvictionPolicy(long windowLength, long lag) {
super(windowLength);
this.lag = lag;
}
/**
* {@inheritDoc}
*
* 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.
*/
@Override
public Action evict(Event event) {
if (evictionContext == null) {
//It is possible to get asked about eviction before we have a context, due to WindowManager
// .compactWindow.
//In this case we should hold on to all the events. When the first watermark is received,
// the context will be set,
//and the events will be reevaluated for eviction
return Action.STOP;
}
long referenceTime = evictionContext.getReferenceTime();
long diff = referenceTime - event.getTimestamp();
if (diff < -lag) {
return Action.STOP;
} else if (diff < 0) {
return Action.KEEP;
} else {
return super.evict(event);
}
}
@Override
public String toString() {
return "WatermarkTimeEvictionPolicy{" + "lag=" + lag + "} " + super.toString();
}
}