Package org.apache.flink.runtime.asyncprocessing

Class AbstractStateIterator<T>

java.lang.Object

org.apache.flink.runtime.asyncprocessing.AbstractStateIterator<T>

All Implemented Interfaces:

StateIterator<T>

Direct Known Subclasses:

ForStListIterator, ForStMapIterator

public abstract class AbstractStateIterator<T>
extends Object
implements StateIterator<T>

A StateIterator implementation to facilitate async data load of iterator. Each state backend could override this class to maintain more variables in need. Any subclass should implement two methods, hasNext() and nextPayloadForContinuousLoading(). The philosophy behind this class is to carry some already loaded elements and provide iterating right on the task thread, and load following ones if needed (determined by hasNext()) by creating **ANOTHER** iterating request. Thus, later it returns another iterator instance, and we continue to apply the user iteration on that instance. The whole elements will be iterated by recursive call of #onNext().

Constructor Summary

Constructors

Constructor	Description
AbstractStateIterator(State originalState, StateRequestType requestType, StateRequestHandler stateHandler, Collection<T> partialResult)

Method Summary

Modifier and Type	Method	Description
protected StateRequestType	getRequestType()
protected abstract boolean	hasNext()	Return whether this iterator has more elements to load besides current cache.
boolean	isEmpty()	Return if this iterator is empty synchronously.
protected abstract Object	nextPayloadForContinuousLoading()	To perform following loading, build and get next payload for the next request.
StateFuture<Void>	onNext(Consumer<T> iterating)	Async iterate the data and call the callback when data is ready.
<U> StateFuture<Collection<U>>	onNext(Function<T,StateFuture<? extends U>> iterating)	Async iterate the data and call the callback when data is ready.
void	onNextSync(Consumer<T> iterating)

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractStateIterator

public AbstractStateIterator(State originalState,
                             StateRequestType requestType,
                             StateRequestHandler stateHandler,
                             Collection<T> partialResult)

Method Detail

hasNext

protected abstract boolean hasNext()

Return whether this iterator has more elements to load besides current cache.

nextPayloadForContinuousLoading

protected abstract Object nextPayloadForContinuousLoading()

To perform following loading, build and get next payload for the next request. This will put into StateRequest.getPayload().

Returns:

the packed payload for next loading.

getRequestType

protected StateRequestType getRequestType()

onNext

public <U> StateFuture<Collection<U>> onNext(Function<T,StateFuture<? extends U>> iterating)

Description copied from interface: StateIterator

Async iterate the data and call the callback when data is ready.

Specified by:

onNext in interface StateIterator<T>

Type Parameters:

U - the type of the inner returned StateFuture's result.

Parameters:

iterating - the data action when it is ready. The return is the state future for chaining.

Returns:

the Future that will trigger when this iterator and all returned state future get its results.

onNext

public StateFuture<Void> onNext(Consumer<T> iterating)

Description copied from interface: StateIterator

Async iterate the data and call the callback when data is ready.

Specified by:

onNext in interface StateIterator<T>

Parameters:

iterating - the data action when it is ready.

Returns:

the Future that will trigger when this iterator ends.

onNextSync

public void onNextSync(Consumer<T> iterating)

isEmpty

public boolean isEmpty()

Description copied from interface: StateIterator

Return if this iterator is empty synchronously.

Specified by:

isEmpty in interface StateIterator<T>