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

Interface SourceFunction.SourceContext<T>

Type Parameters:

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

All Known Implementing Classes:

StreamSource.AutomaticWatermarkContext, StreamSource.ManualWatermarkContext, StreamSource.NonTimestampContext, StreamSource.NonWatermarkContext

Enclosing interface:

SourceFunction<T>

public static interface SourceFunction.SourceContext<T>

Interface that source functions use to communicate with the outside world. Normally sources would just emit elements in a loop using collect(T). If the source is a Checkpointed source it must retrieve the checkpoint lock object and use it to protect state updates and element emission as described in SourceFunction.

Method Summary

Methods

Modifier and Type	Method and Description
void	close() This must be called when closing the source operator to allow the SourceFunction.SourceContext to clean up internal state.
void	collect(T element) Emits one element from the source.
void	collectWithTimestamp(T element, long timestamp) Emits one element from the source with the given timestamp.
void	emitWatermark(Watermark mark) Emits the given Watermark.
Object	getCheckpointLock() Returns the checkpoint lock.

Method Detail

collect

void collect(T element)

Emits one element from the source. The result of System.currentTimeMillis() is set as the timestamp of the emitted element.

Parameters:

element - The element to emit

collectWithTimestamp

void collectWithTimestamp(T element,
                        long timestamp)

Emits one element from the source with the given timestamp.

Parameters:

element - The element to emit

timestamp - The timestamp in milliseconds

emitWatermark

void emitWatermark(Watermark mark)

Emits the given Watermark.

Important: Sources must only manually emit watermarks when they implement EventTimeSourceFunction. Otherwise, elements automatically get the current timestamp assigned at ingress and the system automatically emits watermarks.

Parameters:

mark - The Watermark to emit

getCheckpointLock

Object getCheckpointLock()

Returns the checkpoint lock. Please refer to the explanation about checkpointed sources in SourceFunction.

Returns:

The object to use as the lock.

close

void close()

This must be called when closing the source operator to allow the SourceFunction.SourceContext to clean up internal state.