com.google.cloud.dataflow.sdk.transforms.windowing.FixedWindows.java Source code

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Here is the source code for com.google.cloud.dataflow.sdk.transforms.windowing.FixedWindows.java

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/*
 * Copyright (C) 2015 Google Inc.
 *
 * Licensed 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 com.google.cloud.dataflow.sdk.transforms.windowing;

import com.google.cloud.dataflow.sdk.coders.Coder;
import com.google.cloud.dataflow.sdk.transforms.display.DisplayData;

import org.joda.time.Duration;
import org.joda.time.Instant;

import java.util.Objects;

/**
 * A {@link WindowFn} that windows values into fixed-size timestamp-based windows.
 *
 * <p>For example, in order to partition the data into 10 minute windows:
 * <pre> {@code
 * PCollection<Integer> items = ...;
 * PCollection<Integer> windowedItems = items.apply(
 *   Window.<Integer>into(FixedWindows.of(Duration.standardMinutes(10))));
 * } </pre>
 */
public class FixedWindows extends PartitioningWindowFn<Object, IntervalWindow> {

    /**
     * Size of this window.
     */
    private final Duration size;

    /**
     * Offset of this window.  Windows start at time
     * N * size + offset, where 0 is the epoch.
     */
    private final Duration offset;

    /**
     * Partitions the timestamp space into half-open intervals of the form
     * [N * size, (N + 1) * size), where 0 is the epoch.
     */
    public static FixedWindows of(Duration size) {
        return new FixedWindows(size, Duration.ZERO);
    }

    /**
     * Partitions the timestamp space into half-open intervals of the form
     * [N * size + offset, (N + 1) * size + offset),
     * where 0 is the epoch.
     *
     * @throws IllegalArgumentException if offset is not in [0, size)
     */
    public FixedWindows withOffset(Duration offset) {
        return new FixedWindows(size, offset);
    }

    private FixedWindows(Duration size, Duration offset) {
        if (offset.isShorterThan(Duration.ZERO) || !offset.isShorterThan(size)) {
            throw new IllegalArgumentException("FixedWindows WindowingStrategies must have 0 <= offset < size");
        }
        this.size = size;
        this.offset = offset;
    }

    @Override
    public IntervalWindow assignWindow(Instant timestamp) {
        long start = timestamp.getMillis() - timestamp.plus(size).minus(offset).getMillis() % size.getMillis();
        return new IntervalWindow(new Instant(start), size);
    }

    @Override
    public void populateDisplayData(DisplayData.Builder builder) {
        super.populateDisplayData(builder);
        builder.add(DisplayData.item("size", size).withLabel("Window Duration")).addIfNotDefault(
                DisplayData.item("offset", offset).withLabel("Window Start Offset"), Duration.ZERO);
    }

    @Override
    public Coder<IntervalWindow> windowCoder() {
        return IntervalWindow.getCoder();
    }

    @Override
    public boolean isCompatible(WindowFn<?, ?> other) {
        return this.equals(other);
    }

    public Duration getSize() {
        return size;
    }

    public Duration getOffset() {
        return offset;
    }

    @Override
    public boolean equals(Object object) {
        if (!(object instanceof FixedWindows)) {
            return false;
        }
        FixedWindows other = (FixedWindows) object;
        return getOffset().equals(other.getOffset()) && getSize().equals(other.getSize());
    }

    @Override
    public int hashCode() {
        return Objects.hash(size, offset);
    }
}