org.apache.flink.streaming.api.windowing.evictors.CountEvictor Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.streaming.api.windowing.evictors;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.streaming.api.windowing.windows.Window;
import org.apache.flink.streaming.runtime.operators.windowing.TimestampedValue;
import java.util.Iterator;
/**
* An {@link Evictor} that keeps up to a certain amount of elements.
*
* @param The type of {@link Window Windows} on which this {@code Evictor} can operate.
*/
@PublicEvolving
public class CountEvictor implements Evictor {
private static final long serialVersionUID = 1L;
private final long maxCount;
private final boolean doEvictAfter;
private CountEvictor(long count, boolean doEvictAfter) {
this.maxCount = count;
this.doEvictAfter = doEvictAfter;
}
private CountEvictor(long count) {
this.maxCount = count;
this.doEvictAfter = false;
}
@Override
public void evictBefore(Iterable> elements, int size, W window, EvictorContext ctx) {
if (!doEvictAfter) {
evict(elements, size, ctx);
}
}
@Override
public void evictAfter(Iterable> elements, int size, W window, EvictorContext ctx) {
if (doEvictAfter) {
evict(elements, size, ctx);
}
}
private void evict(Iterable> elements, int size, EvictorContext ctx) {
if (size <= maxCount) {
return;
} else {
int evictedCount = 0;
for (Iterator> iterator = elements.iterator(); iterator.hasNext();){
iterator.next();
evictedCount++;
if (evictedCount > size - maxCount) {
break;
} else {
iterator.remove();
}
}
}
}
/**
* Creates a {@code CountEvictor} that keeps the given number of elements.
* Eviction is done before the window function.
*
* @param maxCount The number of elements to keep in the pane.
*/
public static CountEvictor of(long maxCount) {
return new CountEvictor<>(maxCount);
}
/**
* Creates a {@code CountEvictor} that keeps the given number of elements in the pane
* Eviction is done before/after the window function based on the value of doEvictAfter.
*
* @param maxCount The number of elements to keep in the pane.
* @param doEvictAfter Whether to do eviction after the window function.
*/
public static CountEvictor of(long maxCount, boolean doEvictAfter) {
return new CountEvictor<>(maxCount, doEvictAfter);
}
}