Package org.apache.flink.streaming.util

Class FiniteTestSource<T>

java.lang.Object

org.apache.flink.streaming.util.FiniteTestSource<T>

All Implemented Interfaces:

Serializable, Function, CheckpointListener, SourceFunction<T>

public class FiniteTestSource<T>
extends Object
implements SourceFunction<T>, CheckpointListener

A stream source that: 1) emits a list of elements without allowing checkpoints, 2) then waits for two more checkpoints to complete, 3) then re-emits the same elements before 4) waiting for another two checkpoints and 5) exiting.

This class was written to test the Bulk Writers used by the StreamingFileSink.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.flink.streaming.api.functions.source.legacy.SourceFunction

SourceFunction.SourceContext<T>

Constructor Summary

Constructors

Constructor	Description
FiniteTestSource(Iterable<T> elements)
FiniteTestSource(BooleanSupplier couldExit, long waitTimeOut, Iterable<T> elements)
FiniteTestSource(BooleanSupplier couldExit, Iterable<T> elements)
FiniteTestSource(T... elements)

Method Summary

Modifier and Type	Method	Description
void	cancel()	Cancels the source.
void	notifyCheckpointAborted(long checkpointId)	This method is called as a notification once a distributed checkpoint has been aborted.
void	notifyCheckpointComplete(long checkpointId)	Notifies the listener that the checkpoint with the given checkpointId completed and was committed.
void	run(SourceFunction.SourceContext<T> ctx)	Starts the source.

Methods inherited from class java.lang.Object

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

Constructor Detail

FiniteTestSource

@SafeVarargs
public FiniteTestSource(T... elements)

FiniteTestSource

public FiniteTestSource(Iterable<T> elements)

FiniteTestSource

public FiniteTestSource(@Nullable
                        BooleanSupplier couldExit,
                        long waitTimeOut,
                        Iterable<T> elements)

FiniteTestSource

public FiniteTestSource(@Nullable
                        BooleanSupplier couldExit,
                        Iterable<T> elements)

Method Detail

run

public void run(SourceFunction.SourceContext<T> ctx)
         throws Exception

Description copied from interface: SourceFunction

Starts the source. Implementations use the SourceFunction.SourceContext to emit elements. Sources that checkpoint their state for fault tolerance should use the checkpoint lock to ensure consistency between the bookkeeping and emitting the elements.

Sources that implement CheckpointedFunction must lock on the checkpoint lock checkpoint lock (using a synchronized block) before updating internal state and emitting elements, to make both an atomic operation.

Refer to the top-level class docs for an example.

Specified by:

run in interface SourceFunction<T>

Parameters:

ctx - The context to emit elements to and for accessing locks.

Throws:

Exception

cancel

public void cancel()

Description copied from interface: SourceFunction

Cancels the source. Most sources will have a while loop inside the SourceFunction.run(SourceContext) method. The implementation needs to ensure that the source will break out of that loop after this method is called.

A typical pattern is to have an "volatile boolean isRunning" flag that is set to false in this method. That flag is checked in the loop condition.

In case of an ungraceful shutdown (cancellation of the source operator, possibly for failover), the thread that calls SourceFunction.run(SourceContext) will also be interrupted) by the Flink runtime, in order to speed up the cancellation (to ensure threads exit blocking methods fast, like I/O, blocking queues, etc.). The interruption happens strictly after this method has been called, so any interruption handler can rely on the fact that this method has completed (for example to ignore exceptions that happen after cancellation).

During graceful shutdown (for example stopping a job with a savepoint), the program must cleanly exit the SourceFunction.run(SourceContext) method soon after this method was called. The Flink runtime will NOT interrupt the source thread during graceful shutdown. Source implementors must ensure that no thread interruption happens on any thread that emits records through the SourceContext from the SourceFunction.run(SourceContext) method; otherwise the clean shutdown may fail when threads are interrupted while processing the final records.

Because the SourceFunction cannot easily differentiate whether the shutdown should be graceful or ungraceful, we recommend that implementors refrain from interrupting any threads that interact with the SourceContext at all. You can rely on the Flink runtime to interrupt the source thread in case of ungraceful cancellation. Any additionally spawned threads that directly emit records through the SourceContext should use a shutdown method that does not rely on thread interruption.

Specified by:

cancel in interface SourceFunction<T>

notifyCheckpointComplete

public void notifyCheckpointComplete(long checkpointId)
                              throws Exception

Description copied from interface: CheckpointListener

Notifies the listener that the checkpoint with the given checkpointId completed and was committed.

These notifications are "best effort", meaning they can sometimes be skipped. To behave properly, implementers need to follow the "Checkpoint Subsuming Contract". Please see the class-level JavaDocs for details.

Please note that checkpoints may generally overlap, so you cannot assume that the notifyCheckpointComplete() call is always for the latest prior checkpoint (or snapshot) that was taken on the function/operator implementing this interface. It might be for a checkpoint that was triggered earlier. Implementing the "Checkpoint Subsuming Contract" (see above) properly handles this situation correctly as well.

Please note that throwing exceptions from this method will not cause the completed checkpoint to be revoked. Throwing exceptions will typically cause task/job failure and trigger recovery.

Specified by:

notifyCheckpointComplete in interface CheckpointListener

Parameters:

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

Throws:

Exception - This method can propagate exceptions, which leads to a failure/recovery for the task. Note that this will NOT lead to the checkpoint being revoked.

notifyCheckpointAborted

public void notifyCheckpointAborted(long checkpointId)

Description copied from interface: CheckpointListener

This method is called as a notification once a distributed checkpoint has been aborted.

Important: The fact that a checkpoint has been aborted does NOT mean that the data and artifacts produced between the previous checkpoint and the aborted checkpoint are to be discarded. The expected behavior is as if this checkpoint was never triggered in the first place, and the next successful checkpoint simply covers a longer time span. See the "Checkpoint Subsuming Contract" in the class-level JavaDocs for details.

These notifications are "best effort", meaning they can sometimes be skipped.

This method is very rarely necessary to implement. The "best effort" guarantee, together with the fact that this method should not result in discarding any data (per the "Checkpoint Subsuming Contract") means it is mainly useful for earlier cleanups of auxiliary resources. One example is to pro-actively clear a local per-checkpoint state cache upon checkpoint failure.

Specified by:

notifyCheckpointAborted in interface CheckpointListener

Parameters:

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