Status

Current state: Under Discussion

Discussion thread: TBD

JIRA:   Unable to render Jira issues macro, execution error. Unable to render Jira issues macro, execution error.

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Motivation

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". By delegating the stream topology power to create repartition topic with customized number of partitions gives user more flexibility. Also, for API like #to or #through, KStream has no access to sink topic creation, which means user has to create their own connecting Kafka topic for every single new application which is cumbersome. Thus we are proposing extending the capability of #Produced API to automatically create topics when the target topic has not created.

Public interfaces

We shall expand the Produced API to contain topicName and numPartitions: 

public class Produced<K, V> {
	protected Serde<K> keySerde;
	protected Serde<V> valueSerde;
	protected StreamPartitioner<? super K, ? super V> partitioner;
	protected boolean createTopic; // new
   	protected Integer numPartitions; // new

	public static <K, V> Produced<K, V> with(final Serde<K> keySerde,
                                         	 final Serde<V> valueSerde,
                                             final StreamPartitioner<? super K, ? super V> partitioner,
											 final boolean createTopic,
										     final Integer numPartitions);
}

We also plan to 

Proposed Changes

 When configured with topic name and partition,  KStream application will first issue the topic lookup request and check whether the target topic is already up and running. 

Backward Compatibility 

Rejected Alternatives

N/A