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Status

Current state: Under Discussion

Discussion thread: tba

JIRA:  KAFKA-6037

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

  1. The main motivation of this KIP is stated in the related jira: "Today the downstream sub-topology's parallelism (aka the number of tasks) are purely dependent on the upstream sub-topology's parallelism, which ultimately depends on the source topic's num. partitions. However this does not work perfectly with dynamic scaling scenarios". 
  2. Depending on use-case, we might not need to use repartitioning topic, as keys might not change. 

 

Proposed Changes

 

public class Produced<K, V> {
	protected String topicName;
	protected Boolean repartitionNeeded;
	protected Boolean useAsInternalTopicOnly;
 
	protected Produced(final Produced<K, V> produced) {
    	this.keySerde = produced.keySerde;
   	    this.valueSerde = produced.valueSerde;
   	    this.partitioner = produced.partitioner;
	}
 
	public static <K, V> Produced<K, V> with(String topicName) {
    	return new Produced<>(keySerde, valueSerde, null);
	}




}

 

Public interfaces

 

We try to avoid many overloads by not implementing all the overloaded combinations of related methods.

 

KStream

 

public <VT, VR> KStream<K, VR> join(final KTable<K, VT> other,
                                    final ValueJoiner<? super V, ? super VT, ? extends VR> joiner,
                                    final Joined<K, V, VT> joined,
									final RepartitionHint hintThisStream)
public <VT, VR> KStream<K, VR> leftJoin(final KTable<K, VT> other,
                                        final ValueJoiner<? super V, ? super VT, ? extends VR> joiner,
                                        final Joined<K, V, VT> joined, 
										final RepartitionHint hintThisStream)




public <VO, VR> KStream<K, VR> join(final KStream<K, VO> otherStream,
                                    final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                                    final JoinWindows windows,
                                    final Joined<K, V, VO> joined, 
									final RepartitionHint hintThisStream,
									final RepartitionHint hintOtherStream)
 
public <V1, R> KStream<K, R> join(final KStream<K, V1> other,
                                  final ValueJoiner<? super V, ? super V1, ? extends R> joiner,
                                  final JoinWindows windows,
                                  final Serde<K> keySerde,
                                  final Serde<V> thisValueSerde,
                                  final Serde<V1> otherValueSerde, 
								  final RepartitionHint hintThisStream,
								  final RepartitionHint hintOtherStream)

public <VO, VR> KStream<K, VR> outerJoin(final KStream<K, VO> other,
                                         final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                                         final JoinWindows windows,
                                         final Joined<K, V, VO> joined,
										 final RepartitionHint hintThisStream,
									     final RepartitionHint hintOtherStream)
 
public <V1, R> KStream<K, R> leftJoin(final KStream<K, V1> other,
                                      final ValueJoiner<? super V, ? super V1, ? extends R> joiner,
                                      final JoinWindows windows,
                                      final Serde<K> keySerde,
                                      final Serde<V> thisValSerde,
                                      final Serde<V1> otherValueSerde, 
									  final RepartitionHint hintThisStream,
									  final RepartitionHint hintOtherStream)


public <VO, VR> KStream<K, VR> leftJoin(final KStream<K, VO> other,
                                        final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                                        final JoinWindows windows,
                                        final Joined<K, V, VO> joined, 
										final RepartitionHint hintThisStream,
										final RepartitionHint hintOtherStream)

 

 

 

KGroupedStream

 

public <T> KTable<Windowed<K>, T> aggregate(final Initializer<T> initializer,
                                            final Aggregator<? super K, ? super V, T> aggregator,
                                            final Merger<? super K, T> sessionMerger,
                                            final SessionWindows sessionWindows,
                                            final Serde<T> aggValueSerde,
                                            final org.apache.kafka.streams.processor.StateStoreSupplier<SessionStore> storeSupplier,
											final RepartitionHint repartitionHint)


 
public <T> KTable<K, T> aggregate(final Initializer<T> initializer,
                                  final Aggregator<? super K, ? super V, T> aggregator,
                                  final org.apache.kafka.streams.processor.StateStoreSupplier<KeyValueStore> storeSupplier,
								  final RepartitionHint repartitionHint)




 
public <W extends Window, T> KTable<Windowed<K>, T> aggregate(final Initializer<T> initializer,
                                                              final Aggregator<? super K, ? super V, T> aggregator,
                                                              final Windows<W> windows,
                                                              final org.apache.kafka.streams.processor.StateStoreSupplier<WindowStore> storeSupplier,
															  final RepartitionHint repartitionHint)


 
public KTable<K, V> reduce(final Reducer<V> reducer,
                           final org.apache.kafka.streams.processor.StateStoreSupplier<KeyValueStore> storeSupplier,
						   final RepartitionHint repartitionHint)




 
public <W extends Window> KTable<Windowed<K>, V> reduce(final Reducer<V> reducer,
                                                        final Windows<W> windows,
                                                        final org.apache.kafka.streams.processor.StateStoreSupplier<WindowStore> storeSupplier,
														final RepartitionHint repartitionHint)




 

 

 

Rejected Alternatives

If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.

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