org.apache.flink.streaming.kafka.test.base

Class CustomWatermarkExtractor

java.lang.Object

org.apache.flink.streaming.kafka.test.base.CustomWatermarkExtractor

All Implemented Interfaces:

Serializable, Function, AssignerWithPeriodicWatermarks<KafkaEvent>, TimestampAssigner<KafkaEvent>

public class CustomWatermarkExtractor
extends Object
implements AssignerWithPeriodicWatermarks<KafkaEvent>

A custom AssignerWithPeriodicWatermarks, that simply assumes that the input stream records are strictly ascending.

Flink also ships some built-in convenience assigners, such as the BoundedOutOfOrdernessTimestampExtractor and AscendingTimestampExtractor

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
CustomWatermarkExtractor()

Method Summary

Modifier and Type	Method and Description
long	extractTimestamp(KafkaEvent event, long previousElementTimestamp) Assigns a timestamp to an element, in milliseconds since the Epoch.
Watermark	getCurrentWatermark() Returns the current watermark.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CustomWatermarkExtractor

public CustomWatermarkExtractor()

Method Detail

extractTimestamp

public long extractTimestamp(KafkaEvent event,
                             long previousElementTimestamp)

Description copied from interface: TimestampAssigner

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.

Specified by:

extractTimestamp in interface TimestampAssigner<KafkaEvent>

Parameters:

event - 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.

getCurrentWatermark

@Nullable
public Watermark getCurrentWatermark()

Description copied from interface: AssignerWithPeriodicWatermarks

Returns the current watermark. This method is periodically called by the system to retrieve the current watermark. The method may return null to indicate that no new Watermark is available.

The returned watermark will be emitted only if it is non-null and its timestamp is larger than that of the previously emitted watermark (to preserve the contract of ascending watermarks). If the current watermark is still identical to the previous one, no progress in event time has happened since the previous call to this method. If a null value is returned, or the timestamp of the returned watermark is smaller than that of the last emitted one, then no new watermark will be generated.

The interval in which this method is called and Watermarks are generated depends on ExecutionConfig.getAutoWatermarkInterval().

Specified by:

getCurrentWatermark in interface AssignerWithPeriodicWatermarks<KafkaEvent>

Returns:

Null, if no watermark should be emitted, or the next watermark to emit.

See Also:

Watermark, ExecutionConfig.getAutoWatermarkInterval()