flink-end-to-end-tests/flink-streaming-kafka-test-base/src/main/java/org/apache/flink/streaming/kafka/test/base/CustomWatermarkExtractor.java

/*
 * 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.kafka.test.base;

import org.apache.flink.streaming.api.functions.AssignerWithPeriodicWatermarks;
import org.apache.flink.streaming.api.functions.timestamps.AscendingTimestampExtractor;
import org.apache.flink.streaming.api.functions.timestamps.BoundedOutOfOrdernessTimestampExtractor;
import org.apache.flink.streaming.api.watermark.Watermark;

import javax.annotation.Nullable;

/**
 * A custom {@link AssignerWithPeriodicWatermarks}, that simply assumes that the input stream
 * records are strictly ascending.
 *
 * <p>Flink also ships some built-in convenience assigners, such as the
 * {@link BoundedOutOfOrdernessTimestampExtractor} and {@link AscendingTimestampExtractor}
 */
public class CustomWatermarkExtractor implements AssignerWithPeriodicWatermarks<KafkaEvent> {

	private static final long serialVersionUID = -742759155861320823L;

	private long currentTimestamp = Long.MIN_VALUE;

	@Override
	public long extractTimestamp(KafkaEvent event, long previousElementTimestamp) {
		// the inputs are assumed to be of format (message,timestamp)
		this.currentTimestamp = event.getTimestamp();
		return event.getTimestamp();
	}

	@Nullable
	@Override
	public Watermark getCurrentWatermark() {
		return new Watermark(currentTimestamp == Long.MIN_VALUE ? Long.MIN_VALUE : currentTimestamp - 1);
	}
}