public class FiniteTestSource<T> extends Object implements SourceFunction<T>, CheckpointListener
This class was written to test the Bulk Writers used by the StreamingFileSink.
|Constructor and Description|
|Modifier and Type||Method and Description|
Cancels the source.
This method is called as a notification once a distributed checkpoint has been aborted.
Notifies the listener that the checkpoint with the given
Starts the source.
public FiniteTestSource(@Nullable java.util.function.BooleanSupplier couldExit, long waitTimeOut, Iterable<T> elements)
public void run(SourceFunction.SourceContext<T> ctx) throws Exception
SourceFunction.SourceContextto emit elements. Sources that checkpoint their state for fault tolerance should use the
SourceFunction.SourceContext.getCheckpointLock()checkpoint lock} to ensure consistency between the bookkeeping and emitting the elements.
Sources that implement
CheckpointedFunction must lock on the
SourceFunction.SourceContext.getCheckpointLock() checkpoint lock} checkpoint lock (using a synchronized
block) before updating internal state and emitting elements, to make both an atomic
Refer to the
top-level class docs for an example.
public void cancel()
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
SourceContext from the
SourceFunction.run(SourceContext) method; otherwise the
clean shutdown may fail when threads are interrupted while processing the final records.
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.
public void notifyCheckpointComplete(long checkpointId) throws Exception
checkpointIdcompleted 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.
checkpointId- The ID of the checkpoint that has been completed.
Exception- This method can propagate exceptions, which leads to a failure/recovery for the task. Not that this will NOT lead to the checkpoint being revoked.
public void notifyCheckpointAborted(long checkpointId)
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
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.
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