Status
Current state: Under Discussion
Discussion thread: TBD
JIRA:
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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 final String name; // new, representing topic name protected final String 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 name, final Integer numPartitions); }
We also want to expand Grouped API with a numPartition configuration
public class Grouped<K, V> { protected final Serde<K> keySerde; protected final Serde<V> valueSerde; protected final String name; protected final String numPartitions; // new public static <K, V> Grouped<K, V> with(final String name, final Serde<K> keySerde, final Serde<V> valueSerde, final Integer numPartitions); }
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