org.apache.flink.streaming.runtime.io

Class BarrierTracker

java.lang.Object

org.apache.flink.streaming.runtime.io.BarrierTracker

All Implemented Interfaces:

CheckpointBarrierHandler

@Internal
public class BarrierTracker
extends Object
implements CheckpointBarrierHandler

The BarrierTracker keeps track of what checkpoint barriers have been received from which input channels. Once it has observed all checkpoint barriers for a checkpoint ID, it notifies its listener of a completed checkpoint.

Unlike the BarrierBuffer, the BarrierTracker does not block the input channels that have sent barriers, so it cannot be used to gain "exactly-once" processing guarantees. It can, however, be used to gain "at least once" processing guarantees.

NOTE: This implementation strictly assumes that newer checkpoints have higher checkpoint IDs.

Constructor Summary

Constructors

Constructor and Description
BarrierTracker(InputGate inputGate)

Method Summary

Modifier and Type	Method and Description
void	cleanup() Cleans up all internally held resources.
BufferOrEvent	getNextNonBlocked() Returns the next BufferOrEvent that the operator may consume.
boolean	isEmpty() Checks if the barrier handler has buffered any data internally.
void	registerCheckpointEventHandler(EventListener<CheckpointBarrier> checkpointHandler) Registers the given event handler to be notified on successful checkpoints.

Methods inherited from class java.lang.Object

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

Constructor Detail

BarrierTracker

public BarrierTracker(InputGate inputGate)

Method Detail

getNextNonBlocked

public BufferOrEvent getNextNonBlocked()
                                throws IOException,
                                       InterruptedException

Description copied from interface: CheckpointBarrierHandler

Returns the next BufferOrEvent that the operator may consume. This call blocks until the next BufferOrEvent is available, ir until the stream has been determined to be finished.

Specified by:

getNextNonBlocked in interface CheckpointBarrierHandler

Returns:

The next BufferOrEvent, or null, if the stream is finished.

Throws:

IOException - Thrown, if the network or local disk I/O fails.

InterruptedException - Thrown, if the thread is interrupted while blocking during waiting for the next BufferOrEvent to become available.

registerCheckpointEventHandler

public void registerCheckpointEventHandler(EventListener<CheckpointBarrier> checkpointHandler)

Description copied from interface: CheckpointBarrierHandler

Registers the given event handler to be notified on successful checkpoints.

Specified by:

registerCheckpointEventHandler in interface CheckpointBarrierHandler

Parameters:

checkpointHandler - The handler to register.

cleanup

public void cleanup()

Description copied from interface: CheckpointBarrierHandler

Cleans up all internally held resources.

Specified by:

cleanup in interface CheckpointBarrierHandler

isEmpty

public boolean isEmpty()

Description copied from interface: CheckpointBarrierHandler

Checks if the barrier handler has buffered any data internally.

Specified by:

isEmpty in interface CheckpointBarrierHandler

Returns:

True, if no data is buffered internally, false otherwise.