org.apache.flink.streaming.api.windowing.evictors.Evictor Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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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.evictors;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.functions.RuntimeContext;
import org.apache.flink.metrics.MetricGroup;
import org.apache.flink.streaming.api.windowing.windows.Window;
import org.apache.flink.streaming.runtime.operators.windowing.TimestampedValue;
import java.io.Serializable;
/**
* An {@code Evictor} can remove elements from a pane before/after the evaluation of WindowFunction
* and after the window evaluation gets triggered by a
* {@link org.apache.flink.streaming.api.windowing.triggers.Trigger}
*
* A pane is the bucket of elements that have the same key (assigned by the
* {@link org.apache.flink.api.java.functions.KeySelector}) and same {@link Window}. An element can
* be in multiple panes of it was assigned to multiple windows by the
* {@link org.apache.flink.streaming.api.windowing.assigners.WindowAssigner}. These panes all
* have their own instance of the {@code Evictor}.
*
* @param The type of elements that this {@code Evictor} can evict.
* @param The type of {@link Window Windows} on which this {@code Evictor} can operate.
*/
@PublicEvolving
public interface Evictor extends Serializable {
/**
* Optionally evicts elements. Called before windowing function.
*
* @param elements The elements currently in the pane.
* @param size The current number of elements in the pane.
* @param window The {@link Window}
* @param evictorContext The context for the Evictor
*/
void evictBefore(Iterable> elements, int size, W window, EvictorContext evictorContext);
/**
* Optionally evicts elements. Called after windowing function.
*
* @param elements The elements currently in the pane.
* @param size The current number of elements in the pane.
* @param window The {@link Window}
* @param evictorContext The context for the Evictor
*/
void evictAfter(Iterable> elements, int size, W window, EvictorContext evictorContext);
/**
* A context object that is given to {@link Evictor} methods.
*/
interface EvictorContext {
/**
* Returns the current processing time.
*/
long getCurrentProcessingTime();
/**
* Returns the metric group for this {@link Evictor}. This is the same metric
* group that would be returned from {@link RuntimeContext#getMetricGroup()} in a user
* function.
*
* You must not call methods that create metric objects
* (such as {@link MetricGroup#counter(int)} multiple times but instead call once
* and store the metric object in a field.
*/
MetricGroup getMetricGroup();
/**
* Returns the current watermark time.
*/
long getCurrentWatermark();
}
}