org.apache.flink.streaming.api.windowing.assigners.SlidingProcessingTimeWindows.java Source code

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Here is the source code for org.apache.flink.streaming.api.windowing.assigners.SlidingProcessingTimeWindows.java

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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.assigners;

import com.google.common.collect.Lists;
import org.apache.flink.streaming.api.windowing.time.AbstractTime;
import org.apache.flink.streaming.api.windowing.triggers.ProcessingTimeTrigger;
import org.apache.flink.streaming.api.windowing.triggers.Trigger;
import org.apache.flink.streaming.api.windowing.windows.TimeWindow;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.Collection;
import java.util.List;

/**
 * A {@link WindowAssigner} that windows elements into sliding, time-based windows. The windowing
 * is based on system time. Windows can possibly overlap.
 *
 * <p>
 * For example, in order to window into windows of 1 minute, every 10 seconds:
 * <pre> {@code
 * DataStream<Tuple2<String, Integer>> in = ...;
 * KeyedStream<String, Tuple2<String, Integer>> keyed = in.keyBy(...);
 * WindowedStream<Tuple2<String, Integer>, String, TimeWindows> windowed =
 *   keyed.window(SlidingProcessingTimeWindows.of(Time.of(1, MINUTES), Time.of(10, SECONDS));
 * } </pre>
 */
public class SlidingProcessingTimeWindows extends WindowAssigner<Object, TimeWindow> {
    private static final long serialVersionUID = 1L;

    private final long size;

    private final long slide;

    private transient List<TimeWindow> result;

    private SlidingProcessingTimeWindows(long size, long slide) {
        this.size = size;
        this.slide = slide;
        this.result = Lists.newArrayListWithCapacity((int) (size / slide));
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        this.result = Lists.newArrayListWithCapacity((int) (size / slide));
    }

    @Override
    public Collection<TimeWindow> assignWindows(Object element, long timestamp) {
        result.clear();
        long time = System.currentTimeMillis();
        long lastStart = time - time % slide;
        for (long start = lastStart; start > time - size; start -= slide) {
            result.add(new TimeWindow(start, size));
        }
        return result;
    }

    public long getSize() {
        return size;
    }

    public long getSlide() {
        return slide;
    }

    @Override
    public Trigger<Object, TimeWindow> getDefaultTrigger() {
        return ProcessingTimeTrigger.create();
    }

    @Override
    public String toString() {
        return "SlidingProcessingTimeWindows(" + size + ", " + slide + ")";
    }

    /**
     * Creates a new {@code SlidingProcessingTimeWindows} {@link WindowAssigner} that assigns
     * elements to sliding time windows based on the current processing time.
     *
     * @param size The size of the generated windows.
     * @param slide The slide interval of the generated windows.
     * @return The time policy.
     */
    public static SlidingProcessingTimeWindows of(AbstractTime size, AbstractTime slide) {
        return new SlidingProcessingTimeWindows(size.toMilliseconds(), slide.toMilliseconds());
    }
}