Subtopology
A subtopology is a connected portion of a Kafka Streams processing topology comprising a source and its downstream processors, often separated by an intermediate topic.
Kafka Streams in Action, Second Edition
A sub-topology is a portion of a Kafka Streams topology containing a source node and every processor downstream of that source.
- How it is used
- Organizes Kafka Streams processor graphs around distinct source nodes, especially after repartitioning or when defining independent input streams.
- How deep it goes
- Explains source boundaries, downstream membership, and repartitioning mechanics, but stops short of operational deployment details.
- Examples
- Uses topology descriptions, source-processor-sink graphs, and key-changing streams followed by grouping, aggregation, or joins.
- What you can do after
- Diagnose/debug with topology descriptions by locating source boundaries, downstream processors, and repartition-created sub-topologies.
Read how Kafka Streams in Action, Second Edition explains subtopology →
Apache Kafka in Action
A subtopology is a portion of a Kafka Streams processing topology separated to write to or read from an intermediate topic.
- How it is used
- Uses intermediate repartition topics to divide Kafka Streams processing when key-based joins or aggregations require coordinated data.
- How deep it goes
- Explains the split mechanism, repartition-topic flow, selectKey() example, and network and storage costs.
- Examples
- Demonstrates selectKey() followed by count(), separated by an internal -repartition topic.
- What you can do after
- Evaluate/understand why Kafka Streams splits key-changing processing before joins or aggregations.
Related concepts
- processor topologypart of · A processor topology is a directed graph of source, processor, and sink nodes that defines how records flow through a stream-processing application.
- repartitionproduced by · Repartitioning is the redistribution of records or items across partitions according to a partitioning rule, potentially changing the number of partitions.
- source pointhas part · A source node is a designated origin from which data, flow, traversal, or directed relationships proceed.
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