kafka-streams-internals-StatefulProcessorNode.adoc

StatefulProcessorNode

StatefulProcessorNode is a concrete StreamsGraphNode (as a ProcessorGraphNode) that represents stateful operators of the following:

• KGroupedStreamImpl

• KGroupedTableImpl

• KStreamImpl

• KTableImpl

StatefulProcessorNode is created when:

• KStreamImpl is requested to KStreamImpl.transform and KStreamImpl.flatTransform, KStreamImpl.transformValues, KStreamImpl.flatTransformValues, KStreamImpl.process

• GroupedStreamAggregateBuilder is requested to build (for KStream.groupBy and KStream.groupByKey streaming operators, incl. windowedBy operator with a Windows or a SessionWindows)

• KGroupedTableImpl is requested to doAggregate (for KGroupedTableImpl.aggregate, KGroupedTableImpl.count, and KGroupedTableImpl.reduce operators)

• KTableImpl is requested to suppress

StatefulProcessorNode extends the parent ProcessorGraphNode with the two state-related parameters - the state store names and a StoreBuilder.

Creating StatefulProcessorNode Instance

StatefulProcessorNode takes the following to be created:

• Node name

• ProcessorParameters<K, V>

• Names of the state stores or a StoreBuilder

writeToTopology Method

void writeToTopology(
  InternalTopologyBuilder topologyBuilder)

Note	writeToTopology is part of the StreamsGraphNode Contract to…​FIXME.

writeToTopology requests the given InternalTopologyBuilder to add a processor (with the name and the ProcessorSupplier as defined by the ProcessorParameters).

With state store names given, writeToTopology requests the given InternalTopologyBuilder to connect them with the processor.

With a StoreBuilder given, writeToTopology requests the given InternalTopologyBuilder to add a state store (with the StoreBuilder and the processor).