/*
* 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.Collection;
import java.util.Collections;
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.ProcessingTimeTrigger;
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 sessions based on the current processing
* time. Windows cannot 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(ProcessingTimeSessionWindows.withGap(Time.minutes(1)));
* } </pre>
*/
public class ProcessingTimeSessionWindows extends MergingWindowAssigner<Object, TimeWindow> {
private static final long serialVersionUID = 1L;
protected long sessionTimeout;
protected ProcessingTimeSessionWindows(long sessionTimeout) {
if (sessionTimeout <= 0) {
throw new IllegalArgumentException("ProcessingTimeSessionWindows parameters must satisfy 0 < size");
}
this.sessionTimeout = sessionTimeout;
}
@Override
public Collection<TimeWindow> assignWindows(Object element, long timestamp, WindowAssignerContext context) {
long currentProcessingTime = context.getCurrentProcessingTime();
return Collections.singletonList(new TimeWindow(currentProcessingTime, currentProcessingTime + sessionTimeout));
}
@Override
public Trigger<Object, TimeWindow> getDefaultTrigger(StreamExecutionEnvironment env) {
return ProcessingTimeTrigger.create();
}
@Override
public String toString() {
return "ProcessingTimeSessionWindows(" + sessionTimeout + ")";
}
/**
* Creates a new {@code SessionWindows} {@link WindowAssigner} that assigns
* elements to sessions based on the element timestamp.
*
* @param size The session timeout, i.e. the time gap between sessions
* @return The policy.
*/
public static ProcessingTimeSessionWindows withGap(Time size) {
return new ProcessingTimeSessionWindows(size.toMilliseconds());
}
@Override
public TypeSerializer<TimeWindow> getWindowSerializer(ExecutionConfig executionConfig) {
return new TimeWindow.Serializer();
}
@Override
public boolean isEventTime() {
return false;
}
/**
* Merge overlapping {@link TimeWindow}s.
*/
public void mergeWindows(Collection<TimeWindow> windows, MergeCallback<TimeWindow> c) {
TimeWindow.mergeWindows(windows, c);
}
}