org.apache.flink.streaming.api.operators

Interface StreamOperator<OUT>

Type Parameters:

OUT - The output type of the operator

All Superinterfaces:

Serializable

All Known Subinterfaces:

OneInputStreamOperator<IN,OUT>, TwoInputStreamOperator<IN1,IN2,OUT>

All Known Implementing Classes:

AbstractAlignedProcessingTimeWindowOperator, AbstractCEPPatternOperator, AbstractStreamOperator, AbstractUdfStreamOperator, AccumulatingProcessingTimeWindowOperator, AggregatingProcessingTimeWindowOperator, BoltWrapper, CEPPatternOperator, CoStreamFlatMap, CoStreamMap, EvictingNonKeyedWindowOperator, EvictingWindowOperator, ExtractTimestampsOperator, KeyedCEPPatternOperator, MergedInputsBoltWrapper, NonKeyedWindowOperator, StoppableStreamSource, StreamCounter, StreamFilter, StreamFlatMap, StreamGroupedFold, StreamGroupedReduce, StreamMap, StreamProject, StreamSink, StreamSource, TimestampsAndPeriodicWatermarksOperator, TimestampsAndPunctuatedWatermarksOperator, WindowOperator

@PublicEvolving
public interface StreamOperator<OUT>
extends Serializable

Basic interface for stream operators. Implementers would implement one of OneInputStreamOperator or TwoInputStreamOperator to create operators that process elements.

The class AbstractStreamOperator offers default implementation for the lifecycle and properties methods.

Methods of StreamOperator are guaranteed not to be called concurrently. Also, if using the timer service, timer callbacks are also guaranteed not to be called concurrently with methods on StreamOperator.

Method Summary

Modifier and Type	Method and Description
void	close() This method is called after all records have been added to the operators via the methods OneInputStreamOperator.processElement(StreamRecord), or TwoInputStreamOperator.processElement1(StreamRecord) and TwoInputStreamOperator.processElement2(StreamRecord).
void	dispose() This method is called at the very end of the operator's life, both in the case of a successful completion of the operation, and in the case of a failure and canceling.
ChainingStrategy	getChainingStrategy()
boolean	isInputCopyingDisabled() An operator can return true here to disable copying of its input elements.
void	notifyOfCompletedCheckpoint(long checkpointId) Called when the checkpoint with the given ID is completed and acknowledged on the JobManager.
void	open() This method is called immediately before any elements are processed, it should contain the operator's initialization logic.
void	restoreState(StreamTaskState state, long recoveryTimestamp) Restores the operator state, if this operator's execution is recovering from a checkpoint.
void	setChainingStrategy(ChainingStrategy strategy)
void	setKeyContextElement1(StreamRecord<?> record)
void	setKeyContextElement2(StreamRecord<?> record)
void	setup(StreamTask<?,?> containingTask, StreamConfig config, Output<StreamRecord<OUT>> output) Initializes the operator.
StreamTaskState	snapshotOperatorState(long checkpointId, long timestamp) Called to draw a state snapshot from the operator.

Method Detail

setup

void setup(StreamTask<?,?> containingTask,
           StreamConfig config,
           Output<StreamRecord<OUT>> output)

Initializes the operator. Sets access to the context and the output.

open

void open()
   throws Exception

This method is called immediately before any elements are processed, it should contain the operator's initialization logic.

Throws:

Exception - An exception in this method causes the operator to fail.

close

void close()
    throws Exception

This method is called after all records have been added to the operators via the methods OneInputStreamOperator.processElement(StreamRecord), or TwoInputStreamOperator.processElement1(StreamRecord) and TwoInputStreamOperator.processElement2(StreamRecord).

The method is expected to flush all remaining buffered data. Exceptions during this flushing of buffered should be propagated, in order to cause the operation to be recognized asa failed, because the last data items are not processed properly.

Throws:

Exception - An exception in this method causes the operator to fail.

dispose

void dispose()

This method is called at the very end of the operator's life, both in the case of a successful completion of the operation, and in the case of a failure and canceling. This method is expected to make a thorough effort to release all resources that the operator has acquired.

snapshotOperatorState

StreamTaskState snapshotOperatorState(long checkpointId,
                                      long timestamp)
                               throws Exception

Called to draw a state snapshot from the operator. This method snapshots the operator state (if the operator is stateful) and the key/value state (if it is being used and has been initialized).

Parameters:

checkpointId - The ID of the checkpoint.

timestamp - The timestamp of the checkpoint.

Returns:

The StreamTaskState object, possibly containing the snapshots for the operator and key/value state.

Throws:

Exception - Forwards exceptions that occur while drawing snapshots from the operator and the key/value state.

restoreState

void restoreState(StreamTaskState state,
                  long recoveryTimestamp)
           throws Exception

Restores the operator state, if this operator's execution is recovering from a checkpoint. This method restores the operator state (if the operator is stateful) and the key/value state (if it had been used and was initialized when the snapshot occurred).

This method is called after setup(StreamTask, StreamConfig, Output) and before open().

Parameters:

state - The state of operator that was snapshotted as part of checkpoint from which the execution is restored.

recoveryTimestamp - Global recovery timestamp

Throws:

Exception - Exceptions during state restore should be forwarded, so that the system can properly react to failed state restore and fail the execution attempt.

notifyOfCompletedCheckpoint

void notifyOfCompletedCheckpoint(long checkpointId)
                          throws Exception

Called when the checkpoint with the given ID is completed and acknowledged on the JobManager.

Parameters:

checkpointId - The ID of the checkpoint that has been completed.

Throws:

Exception - Exceptions during checkpoint acknowledgement may be forwarded and will cause the program to fail and enter recovery.

setKeyContextElement1

void setKeyContextElement1(StreamRecord<?> record)
                    throws Exception

Throws:

Exception

setKeyContextElement2

void setKeyContextElement2(StreamRecord<?> record)
                    throws Exception

Throws:

Exception

isInputCopyingDisabled

boolean isInputCopyingDisabled()

An operator can return true here to disable copying of its input elements. This overrides the object-reuse setting on the ExecutionConfig

getChainingStrategy

ChainingStrategy getChainingStrategy()

setChainingStrategy

void setChainingStrategy(ChainingStrategy strategy)