org.apache.flink.streaming.api.functions

Interface TimestampAssigner<T>

Type Parameters:

T - The type of the elements to which this assigner assigns timestamps.

All Superinterfaces:

Function, Serializable

All Known Subinterfaces:

AssignerWithPeriodicWatermarks<T>, AssignerWithPunctuatedWatermarks<T>

All Known Implementing Classes:

AscendingTimestampExtractor, AscendingTimestampExtractor, BoundedOutOfOrdernessTimestampExtractor, IngestionTimeExtractor

public interface TimestampAssigner<T>
extends Function

A TimestampAssigner assigns event time timestamps to elements. These timestamps are used by all functions that operate on event time, for example event time windows.

Timestamps are represented in milliseconds since the Epoch (midnight, January 1, 1970 UTC).

Method Summary

Modifier and Type	Method and Description
long	extractTimestamp(T element, long previousElementTimestamp) Assigns a timestamp to an element, in milliseconds since the Epoch.

Method Detail

extractTimestamp

long extractTimestamp(T element,
                      long previousElementTimestamp)

Assigns a timestamp to an element, in milliseconds since the Epoch.

The method is passed the previously assigned timestamp of the element. That previous timestamp may have been assigned from a previous assigner, by ingestion time. If the element did not carry a timestamp before, this value is Long.MIN_VALUE.

Parameters:

element - The element that the timestamp will be assigned to.

previousElementTimestamp - The previous internal timestamp of the element, or a negative value, if no timestamp has been assigned yet.

Returns:

The new timestamp.