org.apache.flink.runtime.io

Interface PullingAsyncDataInput<T>

All Superinterfaces:

AvailabilityProvider

All Known Implementing Classes:

CheckpointedInputGate, IndexedInputGate, InputGate, InputGateWithMetrics, SingleInputGate, UnionInputGate

@Internal
public interface PullingAsyncDataInput<T>
extends AvailabilityProvider

Interface defining couple of essential methods for asynchronous and non blocking data polling.

For the most efficient usage, user of this class is supposed to call pollNext() until it returns that no more elements are available. If that happens, he should check if input isFinished(). If not, he should wait for AvailabilityProvider.getAvailableFuture() CompletableFuture to be completed. For example:

 AsyncDataInput<T> input = ...;
 while (!input.isFinished()) {
 	Optional<T> next;

 	while (true) {
 		next = input.pollNext();
 		if (!next.isPresent()) {
 			break;
 		}
 		// do something with next
 	}

 	input.getAvailableFuture().get();
 }
 

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	PullingAsyncDataInput.EndOfDataStatus Status for describing if we have reached the end of data.

Nested classes/interfaces inherited from interface org.apache.flink.runtime.io.AvailabilityProvider

AvailabilityProvider.AvailabilityHelper

Field Summary

Fields inherited from interface org.apache.flink.runtime.io.AvailabilityProvider

AVAILABLE

Method Summary

Modifier and Type	Method and Description
PullingAsyncDataInput.EndOfDataStatus	hasReceivedEndOfData() Tells if we consumed all available data.
boolean	isFinished()
Optional<T>	pollNext() Poll the next element.

Methods inherited from interface org.apache.flink.runtime.io.AvailabilityProvider

and, getAvailableFuture, isApproximatelyAvailable, isAvailable, or

Method Detail

pollNext

Optional<T> pollNext()
              throws Exception

Poll the next element. This method should be non blocking.

Returns:

Optional.empty() will be returned if there is no data to return or if isFinished() returns true. Otherwise Optional.of(element).

Throws:

Exception

isFinished

boolean isFinished()

Returns:

true if is finished and for example end of input was reached, false otherwise.

hasReceivedEndOfData

PullingAsyncDataInput.EndOfDataStatus hasReceivedEndOfData()

Tells if we consumed all available data.

Moreover it tells us the reason why there is no more data incoming. If any of the upstream subtasks finished because of the stop-with-savepoint --no-drain, we should not drain the input. See also StopMode.