org.apache.flink.streaming.api.windowing.assigners.SlidingEventTimeWindows Maven / Gradle / Ivy
/*
* 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 org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.streaming.api.windowing.triggers.EventTimeTrigger;
import org.apache.flink.streaming.api.windowing.triggers.Trigger;
import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
/**
* A {@link WindowAssigner} that windows elements into sliding windows based on the timestamp of the
* elements. Windows can possibly overlap.
*
* For example, in order to window into windows of 1 minute, every 10 seconds:
*
*
{@code
* DataStream> in = ...;
* KeyedStream, String> keyed = in.keyBy(...);
* WindowedStream, String, TimeWindow> windowed =
* keyed.window(SlidingEventTimeWindows.of(Time.minutes(1), Time.seconds(10)));
* }
*/
@PublicEvolving
public class SlidingEventTimeWindows extends WindowAssigner {
private static final long serialVersionUID = 1L;
private final long size;
private final long slide;
private final long offset;
protected SlidingEventTimeWindows(long size, long slide, long offset) {
if (Math.abs(offset) >= slide || size <= 0) {
throw new IllegalArgumentException(
"SlidingEventTimeWindows parameters must satisfy "
+ "abs(offset) < slide and size > 0");
}
this.size = size;
this.slide = slide;
this.offset = offset;
}
@Override
public Collection assignWindows(
Object element, long timestamp, WindowAssignerContext context) {
if (timestamp > Long.MIN_VALUE) {
List windows = new ArrayList<>((int) (size / slide));
long lastStart = TimeWindow.getWindowStartWithOffset(timestamp, offset, slide);
for (long start = lastStart; start > timestamp - size; start -= slide) {
windows.add(new TimeWindow(start, start + size));
}
return windows;
} else {
throw new RuntimeException(
"Record has Long.MIN_VALUE timestamp (= no timestamp marker). "
+ "Is the time characteristic set to 'ProcessingTime', or did you forget to call "
+ "'DataStream.assignTimestampsAndWatermarks(...)'?");
}
}
public long getSize() {
return size;
}
public long getSlide() {
return slide;
}
@Override
public Trigger getDefaultTrigger(StreamExecutionEnvironment env) {
return EventTimeTrigger.create();
}
@Override
public String toString() {
return "SlidingEventTimeWindows(" + size + ", " + slide + ")";
}
/**
* Creates a new {@code SlidingEventTimeWindows} {@link WindowAssigner} that assigns elements to
* sliding time windows based on the element timestamp.
*
* @param size The size of the generated windows.
* @param slide The slide interval of the generated windows.
* @return The time policy.
*/
public static SlidingEventTimeWindows of(Time size, Time slide) {
return new SlidingEventTimeWindows(size.toMilliseconds(), slide.toMilliseconds(), 0);
}
/**
* Creates a new {@code SlidingEventTimeWindows} {@link WindowAssigner} that assigns elements to
* time windows based on the element timestamp and offset.
*
* For example, if you want window a stream by hour,but window begins at the 15th minutes of
* each hour, you can use {@code of(Time.hours(1),Time.minutes(15))},then you will get time
* windows start at 0:15:00,1:15:00,2:15:00,etc.
*
*
Rather than that,if you are living in somewhere which is not using UTC±00:00 time, such as
* China which is using UTC+08:00,and you want a time window with size of one day, and window
* begins at every 00:00:00 of local time,you may use {@code of(Time.days(1),Time.hours(-8))}.
* The parameter of offset is {@code Time.hours(-8))} since UTC+08:00 is 8 hours earlier than
* UTC time.
*
* @param size The size of the generated windows.
* @param slide The slide interval of the generated windows.
* @param offset The offset which window start would be shifted by.
* @return The time policy.
*/
public static SlidingEventTimeWindows of(Time size, Time slide, Time offset) {
return new SlidingEventTimeWindows(
size.toMilliseconds(), slide.toMilliseconds(), offset.toMilliseconds());
}
@Override
public TypeSerializer getWindowSerializer(ExecutionConfig executionConfig) {
return new TimeWindow.Serializer();
}
@Override
public boolean isEventTime() {
return true;
}
}