org.apache.flink.streaming.api.functions.timestamps

Class BoundedOutOfOrdernessTimestampExtractor<T>

java.lang.Object

org.apache.flink.streaming.api.functions.timestamps.BoundedOutOfOrdernessTimestampExtractor<T>

All Implemented Interfaces:

Serializable, TimestampAssigner<T>, Function, AssignerWithPeriodicWatermarks<T>

public abstract class BoundedOutOfOrdernessTimestampExtractor<T>
extends Object
implements AssignerWithPeriodicWatermarks<T>

This is a AssignerWithPeriodicWatermarks used to emit Watermarks that lag behind the element with the maximum timestamp (in event time) seen so far by a fixed amount of time, t_late. This can help reduce the number of elements that are ignored due to lateness when computing the final result for a given window, in the case where we know that elements arrive no later than t_late units of time after the watermark that signals that the system event-time has advanced past their (event-time) timestamp.

See Also:

Serialized Form

Field Summary

Fields inherited from interface org.apache.flink.api.common.eventtime.TimestampAssigner

NO_TIMESTAMP

Constructor Summary

Constructors

Constructor and Description
BoundedOutOfOrdernessTimestampExtractor(Time maxOutOfOrderness)

Method Summary

Modifier and Type	Method and Description
abstract long	extractTimestamp(T element) Extracts the timestamp from the given element.
long	extractTimestamp(T element, long previousElementTimestamp) Assigns a timestamp to an element, in milliseconds since the Epoch.
Watermark	getCurrentWatermark() Returns the current watermark.
long	getMaxOutOfOrdernessInMillis()

Methods inherited from class java.lang.Object

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

Constructor Detail

BoundedOutOfOrdernessTimestampExtractor

public BoundedOutOfOrdernessTimestampExtractor(Time maxOutOfOrderness)

Method Detail

getMaxOutOfOrdernessInMillis

public long getMaxOutOfOrdernessInMillis()

extractTimestamp

public abstract long extractTimestamp(T element)

Extracts the timestamp from the given element.

Parameters:

element - The element that the timestamp is extracted from.

Returns:

The new timestamp.

getCurrentWatermark

public final 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<T>

Returns:

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

See Also:

Watermark, ExecutionConfig.getAutoWatermarkInterval()

extractTimestamp

public final long extractTimestamp(T element,
                                   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<T>

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.