org.apache.flink.streaming.api.windowing.triggers.DeltaTrigger Maven / Gradle / Ivy
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* distributed with this work for additional information
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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
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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* See the License for the specific language governing permissions and
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*/
package org.apache.flink.streaming.api.windowing.triggers;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.state.ValueState;
import org.apache.flink.api.common.state.ValueStateDescriptor;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.streaming.api.functions.windowing.delta.DeltaFunction;
import org.apache.flink.streaming.api.windowing.windows.Window;
/**
* A {@link Trigger} that fires based on a {@link DeltaFunction} and a threshold.
*
* This trigger 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.
*
* @param The type of {@link Window Windows} on which this trigger can operate.
*/
@PublicEvolving
public class DeltaTrigger extends Trigger {
private static final long serialVersionUID = 1L;
private final DeltaFunction deltaFunction;
private final double threshold;
private final ValueStateDescriptor stateDesc;
private DeltaTrigger(
double threshold, DeltaFunction deltaFunction, TypeSerializer stateSerializer) {
this.deltaFunction = deltaFunction;
this.threshold = threshold;
stateDesc = new ValueStateDescriptor<>("last-element", stateSerializer);
}
@Override
public TriggerResult onElement(T element, long timestamp, W window, TriggerContext ctx)
throws Exception {
ValueState lastElementState = ctx.getPartitionedState(stateDesc);
if (lastElementState.value() == null) {
lastElementState.update(element);
return TriggerResult.CONTINUE;
}
if (deltaFunction.getDelta(lastElementState.value(), element) > this.threshold) {
lastElementState.update(element);
return TriggerResult.FIRE;
}
return TriggerResult.CONTINUE;
}
@Override
public TriggerResult onEventTime(long time, W window, TriggerContext ctx) {
return TriggerResult.CONTINUE;
}
@Override
public TriggerResult onProcessingTime(long time, W window, TriggerContext ctx)
throws Exception {
return TriggerResult.CONTINUE;
}
@Override
public void clear(W window, TriggerContext ctx) throws Exception {
ctx.getPartitionedState(stateDesc).clear();
}
@Override
public String toString() {
return "DeltaTrigger(" + deltaFunction + ", " + threshold + ")";
}
/**
* Creates a delta trigger from the given threshold and {@code DeltaFunction}.
*
* @param threshold The threshold at which to trigger.
* @param deltaFunction The delta function to use
* @param stateSerializer TypeSerializer for the data elements.
* @param The type of elements on which this trigger can operate.
* @param The type of {@link Window Windows} on which this trigger can operate.
*/
public static DeltaTrigger of(
double threshold, DeltaFunction deltaFunction, TypeSerializer stateSerializer) {
return new DeltaTrigger<>(threshold, deltaFunction, stateSerializer);
}
}