/*
* 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 java.util.ArrayList;
import java.util.Collection;
import java.util.List;
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;
/**
* A {@link WindowAssigner} that windows elements into sliding windows based on the timestamp of the
* elements. 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<Tuple2<String, Integer>, String> keyed = in.keyBy(...);
* WindowedStream<Tuple2<String, Integer>, String, TimeWindow> windowed =
* keyed.window(SlidingEventTimeWindows.of(Time.minutes(1), Time.seconds(10)));
* } </pre>
*/
@PublicEvolving
public class SlidingEventTimeWindows extends WindowAssigner<Object, TimeWindow> {
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 (offset < 0 || offset >= slide || size <= 0) {
throw new IllegalArgumentException("SlidingEventTimeWindows parameters must satisfy 0 <= offset < slide and size > 0");
}
this.size = size;
this.slide = slide;
this.offset = offset;
}
@Override
public Collection<TimeWindow> assignWindows(Object element, long timestamp, WindowAssignerContext context) {
if (timestamp > Long.MIN_VALUE) {
List<TimeWindow> 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<Object, TimeWindow> 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.
*
* <p>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.
*
* <p>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() % slide.toMilliseconds());
}
@Override
public TypeSerializer<TimeWindow> getWindowSerializer(ExecutionConfig executionConfig) {
return new TimeWindow.Serializer();
}
@Override
public boolean isEventTime() {
return true;
}
}