org.apache.flink.runtime.source.coordinator

Class SourceCoordinator<SplitT extends org.apache.flink.api.connector.source.SourceSplit,EnumChkT>

java.lang.Object

org.apache.flink.runtime.source.coordinator.SourceCoordinator<SplitT,EnumChkT>

All Implemented Interfaces:

AutoCloseable, org.apache.flink.api.common.state.CheckpointListener, OperatorCoordinator

@Internal
public class SourceCoordinator<SplitT extends org.apache.flink.api.connector.source.SourceSplit,EnumChkT>
extends Object
implements OperatorCoordinator

The default implementation of the OperatorCoordinator for the Source.

The SourceCoordinator provides an event loop style thread model to interact with the Flink runtime. The coordinator ensures that all the state manipulations are made by its event loop thread. It also helps keep track of the necessary split assignments history per subtask to simplify the SplitEnumerator implementation.

The coordinator maintains a SplitEnumeratorContxt and shares it with the enumerator. When the coordinator receives an action request from the Flink runtime, it sets up the context, and calls corresponding method of the SplitEnumerator to take actions.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SourceCoordinator.WatermarkElement The watermark element for HeapPriorityQueue.

Nested classes/interfaces inherited from interface org.apache.flink.runtime.operators.coordination.OperatorCoordinator

OperatorCoordinator.Context, OperatorCoordinator.Provider, OperatorCoordinator.SubtaskGateway

Field Summary

Fields inherited from interface org.apache.flink.runtime.operators.coordination.OperatorCoordinator

BATCH_CHECKPOINT_ID, NO_CHECKPOINT

Constructor Summary

Constructors

Constructor and Description
SourceCoordinator(String operatorName, org.apache.flink.api.connector.source.Source<?,SplitT,EnumChkT> source, SourceCoordinatorContext<SplitT> context, CoordinatorStore coordinatorStore)
SourceCoordinator(String operatorName, org.apache.flink.api.connector.source.Source<?,SplitT,EnumChkT> source, SourceCoordinatorContext<SplitT> context, CoordinatorStore coordinatorStore, org.apache.flink.api.common.eventtime.WatermarkAlignmentParams watermarkAlignmentParams, String coordinatorListeningID)

Method Summary

Modifier and Type	Method and Description
void	checkpointCoordinator(long checkpointId, CompletableFuture<byte[]> result) Takes a checkpoint of the coordinator.
void	close() This method is called when the coordinator is disposed.
void	executionAttemptFailed(int subtaskId, int attemptNumber, Throwable reason) Called when any subtask execution attempt of the task running the coordinated operator is failed/canceled.
void	executionAttemptReady(int subtask, int attemptNumber, OperatorCoordinator.SubtaskGateway gateway) This is called when a subtask execution attempt of the Operator becomes ready to receive events.
ExecutorService	getCoordinatorExecutor()
org.apache.flink.api.connector.source.SplitEnumerator<SplitT,EnumChkT>	getEnumerator()
void	handleEventFromOperator(int subtask, int attemptNumber, OperatorEvent event) Hands an OperatorEvent coming from a parallel Operator instance (one attempt of the parallel subtasks).
CompletableFuture<Integer>	inferSourceParallelismAsync(int parallelismInferenceUpperBound, long dataVolumePerTask)
void	notifyCheckpointAborted(long checkpointId) We override the method here to remove the checked exception.
void	notifyCheckpointComplete(long checkpointId) We override the method here to remove the checked exception.
void	resetToCheckpoint(long checkpointId, byte[] checkpointData) Resets the coordinator to the given checkpoint.
void	start() Starts the coordinator.
void	subtaskReset(int subtaskId, long checkpointId) Called if a subtask is recovered as part of a partial failover, meaning a failover handled by the scheduler's failover strategy (by default recovering a pipelined region).
boolean	supportsBatchSnapshot() Whether the enumerator supports batch snapshot.

Methods inherited from class java.lang.Object

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

Constructor Detail

SourceCoordinator

public SourceCoordinator(String operatorName,
                         org.apache.flink.api.connector.source.Source<?,SplitT,EnumChkT> source,
                         SourceCoordinatorContext<SplitT> context,
                         CoordinatorStore coordinatorStore)

SourceCoordinator

public SourceCoordinator(String operatorName,
                         org.apache.flink.api.connector.source.Source<?,SplitT,EnumChkT> source,
                         SourceCoordinatorContext<SplitT> context,
                         CoordinatorStore coordinatorStore,
                         org.apache.flink.api.common.eventtime.WatermarkAlignmentParams watermarkAlignmentParams,
                         @Nullable
                         String coordinatorListeningID)

Method Detail

start

public void start()
           throws Exception

Description copied from interface: OperatorCoordinator

Starts the coordinator. This method is called once at the beginning, before any other methods.

Specified by:

start in interface OperatorCoordinator

Throws:

Exception - Any exception thrown from this method causes a full job failure.

close

public void close()
           throws Exception

Description copied from interface: OperatorCoordinator

This method is called when the coordinator is disposed. This method should release currently held resources. Exceptions in this method do not cause the job to fail.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface OperatorCoordinator

Throws:

Exception

handleEventFromOperator

public void handleEventFromOperator(int subtask,
                                    int attemptNumber,
                                    OperatorEvent event)

Description copied from interface: OperatorCoordinator

Hands an OperatorEvent coming from a parallel Operator instance (one attempt of the parallel subtasks).

Specified by:

handleEventFromOperator in interface OperatorCoordinator

executionAttemptFailed

public void executionAttemptFailed(int subtaskId,
                                   int attemptNumber,
                                   @Nullable
                                   Throwable reason)

Description copied from interface: OperatorCoordinator

Called when any subtask execution attempt of the task running the coordinated operator is failed/canceled.

This method is called every time an execution attempt is failed/canceled, regardless of whether there it is caused by a partial failover or a global failover.

Specified by:

executionAttemptFailed in interface OperatorCoordinator

subtaskReset

public void subtaskReset(int subtaskId,
                         long checkpointId)

Description copied from interface: OperatorCoordinator

Called if a subtask is recovered as part of a partial failover, meaning a failover handled by the scheduler's failover strategy (by default recovering a pipelined region). The method is invoked for each subtask involved in that partial failover.

In contrast to this method, the OperatorCoordinator.resetToCheckpoint(long, byte[]) method is called in the case of a global failover, which is the case when the coordinator (JobManager) is recovered.

Note that this method will not be called if an execution attempt of a subtask failed, if the subtask is not entirely failed, i.e. if the subtask has other execution attempts that are not failed/canceled.

Specified by:

subtaskReset in interface OperatorCoordinator

executionAttemptReady

public void executionAttemptReady(int subtask,
                                  int attemptNumber,
                                  OperatorCoordinator.SubtaskGateway gateway)

Description copied from interface: OperatorCoordinator

This is called when a subtask execution attempt of the Operator becomes ready to receive events. The given SubtaskGateway can be used to send events to the execution attempt.

The given SubtaskGateway is bound to that specific execution attempt that became ready. All events sent through the gateway target that execution attempt; if the attempt is no longer running by the time the event is sent, then the events are failed.

Specified by:

executionAttemptReady in interface OperatorCoordinator

supportsBatchSnapshot

public boolean supportsBatchSnapshot()

Whether the enumerator supports batch snapshot. Note the enumerator is created either during resetting the coordinator to a checkpoint, or when the coordinator is started.

Specified by:

supportsBatchSnapshot in interface OperatorCoordinator

checkpointCoordinator

public void checkpointCoordinator(long checkpointId,
                                  CompletableFuture<byte[]> result)

Description copied from interface: OperatorCoordinator

Takes a checkpoint of the coordinator. The checkpoint is identified by the given ID.

To confirm the checkpoint and store state in it, the given CompletableFuture must be completed with the state. To abort or dis-confirm the checkpoint, the given CompletableFuture must be completed exceptionally. In any case, the given CompletableFuture must be completed in some way, otherwise the checkpoint will not progress.

Exactly-once Semantics

The semantics are defined as follows:

• The point in time when the checkpoint future is completed is considered the point in time when the coordinator's checkpoint takes place.
• The OperatorCoordinator implementation must have a way of strictly ordering the sending of events and the completion of the checkpoint future (for example the same thread does both actions, or both actions are guarded by a mutex).
• Every event sent before the checkpoint future is completed is considered before the checkpoint.
• Every event sent after the checkpoint future is completed is considered to be after the checkpoint.

Specified by:

checkpointCoordinator in interface OperatorCoordinator

notifyCheckpointComplete

public void notifyCheckpointComplete(long checkpointId)

Description copied from interface: OperatorCoordinator

We override the method here to remove the checked exception. Please check the Java docs of CheckpointListener.notifyCheckpointComplete(long) for more detail semantic of the method.

Specified by:

notifyCheckpointComplete in interface org.apache.flink.api.common.state.CheckpointListener

Specified by:

notifyCheckpointComplete in interface OperatorCoordinator

notifyCheckpointAborted

public void notifyCheckpointAborted(long checkpointId)

Description copied from interface: OperatorCoordinator

We override the method here to remove the checked exception. Please check the Java docs of CheckpointListener.notifyCheckpointAborted(long) for more detail semantic of the method.

Specified by:

notifyCheckpointAborted in interface org.apache.flink.api.common.state.CheckpointListener

Specified by:

notifyCheckpointAborted in interface OperatorCoordinator

resetToCheckpoint

public void resetToCheckpoint(long checkpointId,
                              @Nullable
                              byte[] checkpointData)
                       throws Exception

Description copied from interface: OperatorCoordinator

Resets the coordinator to the given checkpoint. When this method is called, the coordinator can discard all other in-flight working state. All subtasks will also have been reset to the same checkpoint.

This method is called in the case of a global failover of the system, which means a failover of the coordinator (JobManager). This method is not invoked on a partial failover; partial failovers call the OperatorCoordinator.subtaskReset(int, long) method for the involved subtasks.

This method is expected to behave synchronously with respect to other method calls and calls to Context methods. For example, Events being sent by the Coordinator after this method returns are assumed to take place after the checkpoint that was restored.

This method is called with a null state argument in the following situations:

• There is a recovery and there was no completed checkpoint yet.
• There is a recovery from a completed checkpoint/savepoint but it contained no state for the coordinator.

In both cases, the coordinator should reset to an empty (new) state.

Restoring implicitly notifies of Checkpoint Completion

Restoring to a checkpoint is a way of confirming that the checkpoint is complete. It is safe to commit side-effects that are predicated on checkpoint completion after this call.

Even if no call to OperatorCoordinator.notifyCheckpointComplete(long) happened, the checkpoint can still be complete (for example when a system failure happened directly after committing the checkpoint, before calling the OperatorCoordinator.notifyCheckpointComplete(long) method).

Specified by:

resetToCheckpoint in interface OperatorCoordinator

Throws:

Exception

getEnumerator

@VisibleForTesting
public org.apache.flink.api.connector.source.SplitEnumerator<SplitT,EnumChkT> getEnumerator()

getCoordinatorExecutor

@VisibleForTesting
public ExecutorService getCoordinatorExecutor()

inferSourceParallelismAsync

public CompletableFuture<Integer> inferSourceParallelismAsync(int parallelismInferenceUpperBound,
                                                              long dataVolumePerTask)