/*
* 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.streaming.api.windowing.time.Time;
/**
* This is a special window assigner used to tell the system to use the
* <i>"Fast Aligned Processing Time Window Operator"</i> for windowing.
*
* <p>Prior Flink versions used that operator automatically for simple processing time
* windows (tumbling and sliding) when no custom trigger and no evictor was specified.
* In the current Flink version, that operator is only used when programs explicitly
* specify this window assigner. This is only intended for special cases where programs relied on
* the better performance of the fast aligned window operator, and are willing to accept the lack
* of support for various features as indicated below:
*
* <ul>
* <li>No custom state backend can be selected, the operator always stores data on the Java heap.</li>
* <li>The operator does not support key groups, meaning it cannot change the parallelism.</li>
* <li>Future versions of Flink may not be able to resume from checkpoints/savepoints taken by this
* operator.</li>
* </ul>
*
* <p>Future implementation plans: We plan to add some of the optimizations used by this operator to
* the general window operator, so that future versions of Flink will not have the performance/functionality
* trade-off any more.
*
* <p>Note on implementation: The concrete operator instantiated by this assigner is either the
* {@link org.apache.flink.streaming.runtime.operators.windowing.AggregatingProcessingTimeWindowOperator}
* or {@link org.apache.flink.streaming.runtime.operators.windowing.AccumulatingProcessingTimeWindowOperator}.
*/
@PublicEvolving
public final class TumblingAlignedProcessingTimeWindows extends BaseAlignedWindowAssigner {
private static final long serialVersionUID = -6217477609512299842L;
public TumblingAlignedProcessingTimeWindows(long size) {
super(size);
}
/**
* Creates a new {@code TumblingAlignedProcessingTimeWindows} {@link WindowAssigner} that assigns
* elements to time windows based on the element timestamp.
*
* @param size The size of the generated windows.
*/
public static TumblingAlignedProcessingTimeWindows of(Time size) {
return new TumblingAlignedProcessingTimeWindows(size.toMilliseconds());
}
}