E - The type of events returned by the reader.IterT - The type of the iterator that produces the events. This type exists to make the
conversion between iterator and IteratorSourceSplit type safe.SplitT - The concrete type of the IteratorSourceSplit that creates and converts
the iterator that produces this reader's elements.public class IteratorSourceReader<E,IterT extends Iterator<E>,SplitT extends IteratorSourceSplit<E,IterT>> extends Object implements SourceReader<E,SplitT>
SourceReader that returns the values of an iterator, supplied via an IteratorSourceSplit.
The IteratorSourceSplit is also responsible for taking the current iterator and
turning it back into a split for checkpointing.
| Constructor and Description |
|---|
IteratorSourceReader(SourceReaderContext context) |
| Modifier and Type | Method and Description |
|---|---|
void |
addSplits(List<SplitT> splits)
Adds a list of splits for this reader to read.
|
void |
close() |
CompletableFuture<Void> |
isAvailable()
Returns a future that signals that data is available from the reader.
|
void |
notifyNoMoreSplits()
This method is called when the reader is notified that it will not receive any further
splits.
|
InputStatus |
pollNext(ReaderOutput<E> output)
Poll the next available record into the
SourceOutput. |
List<SplitT> |
snapshotState(long checkpointId)
Checkpoint on the state of the source.
|
void |
start()
Start the reader.
|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waithandleSourceEvents, notifyCheckpointCompletenotifyCheckpointAbortedpublic IteratorSourceReader(SourceReaderContext context)
public void start()
SourceReaderstart in interface SourceReader<E,SplitT extends IteratorSourceSplit<E,IterT>>public InputStatus pollNext(ReaderOutput<E> output)
SourceReaderSourceOutput.
The implementation must make sure this method is non-blocking.
Although the implementation can emit multiple records into the given SourceOutput, it is
recommended not doing so. Instead, emit one record into the SourceOutput and return a InputStatus.MORE_AVAILABLE to let the caller thread know there are more records available.
pollNext in interface SourceReader<E,SplitT extends IteratorSourceSplit<E,IterT>>public CompletableFuture<Void> isAvailable()
SourceReaderOnce the future completes, the runtime will keep calling the SourceReader.pollNext(ReaderOutput) method until that methods returns a status other than InputStatus.MORE_AVAILABLE. After that the, the runtime will again call this method to
obtain the next future. Once that completes, it will again call SourceReader.pollNext(ReaderOutput) and so on.
The contract is the following: If the reader has data available, then all futures previously returned by this method must eventually complete. Otherwise the source might stall indefinitely.
It is not a problem to have occasional "false positives", meaning to complete a future
even if no data is available. However, one should not use an "always complete" future in
cases no data is available, because that will result in busy waiting loops calling pollNext(...) even though no data is available.
isAvailable in interface SourceReader<E,SplitT extends IteratorSourceSplit<E,IterT>>public void addSplits(List<SplitT> splits)
SourceReaderSplitEnumeratorContext.assignSplit(SourceSplit, int) or SplitEnumeratorContext.assignSplits(SplitsAssignment).addSplits in interface SourceReader<E,SplitT extends IteratorSourceSplit<E,IterT>>splits - The splits assigned by the split enumerator.public void notifyNoMoreSplits()
SourceReaderIt is triggered when the enumerator calls SplitEnumeratorContext.signalNoMoreSplits(int) with the reader's parallel subtask.
notifyNoMoreSplits in interface SourceReader<E,SplitT extends IteratorSourceSplit<E,IterT>>public List<SplitT> snapshotState(long checkpointId)
SourceReadersnapshotState in interface SourceReader<E,SplitT extends IteratorSourceSplit<E,IterT>>public void close()
throws Exception
close in interface AutoCloseableExceptionCopyright © 2014–2021 The Apache Software Foundation. All rights reserved.