org.apache.flink.streaming.runtime.operators

Class GenericWriteAheadSink<IN>

java.lang.Object

org.apache.flink.streaming.api.operators.AbstractStreamOperator<IN>

org.apache.flink.streaming.runtime.operators.GenericWriteAheadSink<IN>

Type Parameters:

IN - Type of the elements emitted by this sink

All Implemented Interfaces:

Serializable, OneInputStreamOperator<IN,IN>, StreamOperator<IN>

public abstract class GenericWriteAheadSink<IN>
extends AbstractStreamOperator<IN>
implements OneInputStreamOperator<IN,IN>

Generic Sink that emits its input elements into an arbitrary backend. This sink is integrated with the checkpointing mechanism and can provide exactly-once guarantees; depending on the storage backend and sink/committer implementation.

Incoming records are stored within a AbstractStateBackend, and only committed if a checkpoint is completed.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GenericWriteAheadSink.ExactlyOnceState This state is used to keep a list of all StateHandles (essentially references to past OperatorStates) that were used since the last completed checkpoint.

Nested classes/interfaces inherited from class org.apache.flink.streaming.api.operators.AbstractStreamOperator

AbstractStreamOperator.CountingOutput

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.slf4j.Logger	LOG
protected org.apache.flink.api.common.typeutils.TypeSerializer<IN>	serializer

Fields inherited from class org.apache.flink.streaming.api.operators.AbstractStreamOperator

chainingStrategy, metrics, output

Constructor Summary

Constructors

Constructor and Description
GenericWriteAheadSink(CheckpointCommitter committer, org.apache.flink.api.common.typeutils.TypeSerializer<IN> serializer, String jobID)

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	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	processElement(StreamRecord<IN> element) Processes one element that arrived at this operator.
void	processWatermark(Watermark mark) Processes a Watermark.
void	restoreState(StreamTaskState state) Restores the operator state, if this operator's execution is recovering from a checkpoint.
protected abstract boolean	sendValues(Iterable<IN> value, long timestamp) Write the given element into the backend.
StreamTaskState	snapshotOperatorState(long checkpointId, long timestamp) Called to draw a state snapshot from the operator.

Methods inherited from class org.apache.flink.streaming.api.operators.AbstractStreamOperator

dispose, getChainingStrategy, getContainingTask, getCurrentProcessingTime, getExecutionConfig, getMetricGroup, getOperatorConfig, getPartitionedState, getPartitionedState, getRuntimeContext, getStateBackend, getUserCodeClassloader, registerTimer, setChainingStrategy, setKeyContext, setKeyContextElement1, setKeyContextElement2, setup

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.flink.streaming.api.operators.StreamOperator

dispose, getChainingStrategy, getMetricGroup, setChainingStrategy, setKeyContextElement1, setKeyContextElement2, setup

Field Detail

LOG

protected static final org.slf4j.Logger LOG

serializer

protected final org.apache.flink.api.common.typeutils.TypeSerializer<IN> serializer

Constructor Detail

GenericWriteAheadSink

public GenericWriteAheadSink(CheckpointCommitter committer,
                             org.apache.flink.api.common.typeutils.TypeSerializer<IN> serializer,
                             String jobID)
                      throws Exception

Throws:

Exception

Method Detail

open

public void open()
          throws Exception

Description copied from class: AbstractStreamOperator

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

The default implementation does nothing.

Specified by:

open in interface StreamOperator<IN>

Overrides:

open in class AbstractStreamOperator<IN>

Throws:

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

close

public void close()
           throws Exception

Description copied from class: AbstractStreamOperator

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.

Specified by:

close in interface StreamOperator<IN>

Overrides:

close in class AbstractStreamOperator<IN>

Throws:

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

snapshotOperatorState

public StreamTaskState snapshotOperatorState(long checkpointId,
                                             long timestamp)
                                      throws Exception

Description copied from interface: StreamOperator

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).

Specified by:

snapshotOperatorState in interface StreamOperator<IN>

Overrides:

snapshotOperatorState in class AbstractStreamOperator<IN>

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

public void restoreState(StreamTaskState state)
                  throws Exception

Description copied from interface: StreamOperator

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 StreamOperator.setup(StreamTask, StreamConfig, Output) and before StreamOperator.open().

Specified by:

restoreState in interface StreamOperator<IN>

Overrides:

restoreState in class AbstractStreamOperator<IN>

Parameters:

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

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

public void notifyOfCompletedCheckpoint(long checkpointId)
                                 throws Exception

Description copied from interface: StreamOperator

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

Specified by:

notifyOfCompletedCheckpoint in interface StreamOperator<IN>

Overrides:

notifyOfCompletedCheckpoint in class AbstractStreamOperator<IN>

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.

sendValues

protected abstract boolean sendValues(Iterable<IN> value,
                                      long timestamp)
                               throws Exception

Write the given element into the backend.

Parameters:

value - value to be written

Returns:

true, if the sending was successful, false otherwise

Throws:

Exception

processElement

public void processElement(StreamRecord<IN> element)
                    throws Exception

Description copied from interface: OneInputStreamOperator

Processes one element that arrived at this operator. This method is guaranteed to not be called concurrently with other methods of the operator.

Specified by:

processElement in interface OneInputStreamOperator<IN,IN>

Throws:

Exception

processWatermark

public void processWatermark(Watermark mark)
                      throws Exception

Description copied from interface: OneInputStreamOperator

Processes a Watermark. This method is guaranteed to not be called concurrently with other methods of the operator.

Specified by:

processWatermark in interface OneInputStreamOperator<IN,IN>

Throws:

Exception

See Also:

Watermark