org.apache.flink.streaming.api.functions.TimestampExtractor 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.functions;
import org.apache.flink.api.common.functions.Function;
import org.apache.flink.streaming.api.functions.timestamps.AscendingTimestampExtractor;
/**
* Interface for user functions that extract timestamps from elements.
*
* The extractor must also keep track of the current watermark. The system will periodically
* retrieve this watermark using {@link #getCurrentWatermark()} and submit it throughout the
* topology.
*
*
Note: If you know that timestamps are monotonically increasing you can use
* {@link AscendingTimestampExtractor}. This will keep track of watermarks.
*
* @param The type of the elements that this function can extract timestamps from
*
* @deprecated This class has been replaced by {@link AssignerWithPeriodicWatermarks} and
* {@link AssignerWithPunctuatedWatermarks}
*
* @see AssignerWithPeriodicWatermarks
* @see AssignerWithPunctuatedWatermarks
*/
@Deprecated
public interface TimestampExtractor extends Function {
/**
* Extracts a timestamp from an element.
*
* @param element The element that the timestamp is extracted from.
* @param currentTimestamp The current internal timestamp of the element.
* @return The new timestamp.
*/
long extractTimestamp(T element, long currentTimestamp);
/**
* Asks the extractor if it wants to emit a watermark now that it has seen the given element.
* This is called right after {@link #extractTimestamp}. With the same element. The method
* can return {@code Long.MIN_VALUE} to indicate that no watermark should be emitted, a value of 0 or
* greater will be emitted as a watermark if it is higher than the last-emitted watermark.
*
* @param element The element that we last saw.
* @param currentTimestamp The current timestamp of the element that we last saw.
* @return {@code Long.MIN_VALUE} if no watermark should be emitted, positive value for
* emitting this value as a watermark.
*/
long extractWatermark(T element, long currentTimestamp);
/**
* Returns the current watermark. This is periodically called by the system to determine
* the current watermark and forward it.
*
* @see org.apache.flink.streaming.api.watermark.Watermark
*/
long getCurrentWatermark();
}