public class FiniteTestSource<T> extends Object implements SourceFunction<T>, CheckpointListener
This class was written to test the Bulk Writers used by the StreamingFileSink.
SourceFunction.SourceContext<T>
Constructor and Description |
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FiniteTestSource(Iterable<T> elements) |
FiniteTestSource(T... elements) |
Modifier and Type | Method and Description |
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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)
This method is called as a notification once a distributed checkpoint has been completed.
|
void |
run(SourceFunction.SourceContext<T> ctx)
Starts the source.
|
@SafeVarargs public FiniteTestSource(T... elements)
public void run(SourceFunction.SourceContext<T> ctx) throws Exception
SourceFunction
SourceFunction.SourceContext
emit elements.
Sources that implement CheckpointedFunction
must lock on the checkpoint
lock (using a synchronized block) before updating internal state and emitting elements, to
make both an atomic operation:
public class ExampleCountSource implements SourceFunction<Long>, CheckpointedFunction {
private long count = 0L;
private volatile boolean isRunning = true;
private transient ListState<Long> checkpointedCount;
public void run(SourceContext<T> ctx) {
while (isRunning && count < 1000) {
// this synchronized block ensures that state checkpointing,
// internal state updates and emission of elements are an atomic operation
synchronized (ctx.getCheckpointLock()) {
ctx.collect(count);
count++;
}
}
}
public void cancel() {
isRunning = false;
}
public void initializeState(FunctionInitializationContext context) {
this.checkpointedCount = context
.getOperatorStateStore()
.getListState(new ListStateDescriptor<>("count", Long.class));
if (context.isRestored()) {
for (Long count : this.checkpointedCount.get()) {
this.count = count;
}
}
}
public void snapshotState(FunctionSnapshotContext context) {
this.checkpointedCount.clear();
this.checkpointedCount.add(count);
}
}
run
in interface SourceFunction<T>
ctx
- The context to emit elements to and for accessing locks.Exception
public void cancel()
SourceFunction
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.
When a source is canceled, the executing thread will also be interrupted (via Thread.interrupt()
). The interruption happens strictly after this method has been called, so
any interruption handler can rely on the fact that this method has completed. It is good
practice to make any flags altered by this method "volatile", in order to guarantee the
visibility of the effects of this method to any interruption handler.
cancel
in interface SourceFunction<T>
public void notifyCheckpointComplete(long checkpointId) throws Exception
CheckpointListener
Note that any exception during this method will not cause the checkpoint to fail any more.
notifyCheckpointComplete
in interface CheckpointListener
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)
CheckpointListener
notifyCheckpointAborted
in interface CheckpointListener
checkpointId
- The ID of the checkpoint that has been aborted.Copyright © 2014–2021 The Apache Software Foundation. All rights reserved.