KIP-159 — Introducing Rich functions to Streams

Discussion Streams

Introduces Rich function interfaces (RichValueMapper, RichKeyValueMapper, etc.) to Kafka Streams that expose the RecordContext (topic, partition, offset, timestamp, headers) and the record key to value-only operators such as ValueMapper and ValueJoiner. Existing un-rich interfaces provided no access to record metadata or the message key, blocking use cases like conditional routing based on headers or key-aware transformations.

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