org.apache.flink.streaming.api.functions.source

Interface SourceFunction.SourceContext<T>

Type Parameters:

T - The type of the elements produced by the source.

Enclosing interface:

SourceFunction<T>

@Public
public static interface SourceFunction.SourceContext<T>

Interface that source functions use to emit elements, and possibly watermarks.

Method Summary

Modifier and Type	Method and Description
void	close() This method is called by the system to shut down the context.
void	collect(T element) Emits one element from the source, without attaching a timestamp.
void	collectWithTimestamp(T element, long timestamp) Emits one element from the source, and attaches the given timestamp.
void	emitWatermark(Watermark mark) Emits the given Watermark.
Object	getCheckpointLock() Returns the checkpoint lock.
void	markAsTemporarilyIdle() Marks the source to be temporarily idle.

Method Detail

collect

void collect(T element)

Emits one element from the source, without attaching a timestamp. In most cases, this is the default way of emitting elements.

The element will have no timestamp initially. If timestamps and watermarks are required, for example for event-time windows, timers, or joins, then you need to assign a timestamp via DataStream.assignTimestampsAndWatermarks(WatermarkStrategy) and set a strategy that assigns timestamps (for example using WatermarkStrategy.withTimestampAssigner(TimestampAssignerSupplier)).

Parameters:

element - The element to emit

collectWithTimestamp

@PublicEvolving
void collectWithTimestamp(T element,
                                          long timestamp)

Emits one element from the source, and attaches the given timestamp.

Parameters:

element - The element to emit

timestamp - The timestamp in milliseconds since the Epoch

emitWatermark

@PublicEvolving
void emitWatermark(Watermark mark)

Emits the given Watermark. A Watermark of value t declares that no elements with a timestamp t' <= t will occur any more. If further such elements will be emitted, those elements are considered late.

Parameters:

mark - The Watermark to emit

markAsTemporarilyIdle

@PublicEvolving
void markAsTemporarilyIdle()

Marks the source to be temporarily idle. This tells the system that this source will temporarily stop emitting records and watermarks for an indefinite amount of time.

Source functions should make a best effort to call this method as soon as they acknowledge themselves to be idle. The system will consider the source to resume activity again once SourceContext#collect(T), SourceContext#collectWithTimestamp(T, long), or emitWatermark(Watermark) is called to emit elements or watermarks from the source.

getCheckpointLock

Object getCheckpointLock()

Returns the checkpoint lock. Please refer to the class-level comment in SourceFunction for details about how to write a consistent checkpointed source.

Returns:

The object to use as the lock

close

void close()

This method is called by the system to shut down the context.