I’m using the @KafkaOutput annotation in my Azure Function App to write to my Kafka topic using data from another Kafka topic.

    fun run(
        @KafkaTrigger(
            name = "kafkaTrigger",
            topic = "%KafkaGolfSwingInputTopic%",
            brokerList="%KafkaBrokerList%",
            username = "%KafkaUsername%",
            password = "%KafkaPassword%",
            authenticationMode = BrokerAuthenticationMode.PLAIN,
            protocol = BrokerProtocol.SASLSSL,
            consumerGroup = "%KafkaConsumerGroup%",
            avroSchema = GOLF_SWING_EVENT_AVRO_SCHEMA,
        ) kafkaEventData: GolfSwingEventValue?,
        @KafkaOutput(
            name = "kafkaOutput",
            topic = "%KafkaAssessmentSwingOutputTopic%",
            brokerList="%KafkaBrokerList%",
            username = "%KafkaUsername%",
            password = "%KafkaPassword%",
            authenticationMode = BrokerAuthenticationMode.PLAIN,
            protocol = BrokerProtocol.SASLSSL,
        ) kafkaOutputBinding: OutputBinding<AssessmentSwingEventValue>,
        context: ExecutionContext
    ) {
...
        kafkaOutputBinding.setValue(assessmentSwingEventValue)

Right now I’m just getting the value, which of course is all I’m sending as the OutputBinding. But I have not been able to find a way to write the value AND the key.
We need the key for partitioning. Nothing I have found so far shows a way to specify that you want a key and a value in the output.

I’m assuming I may need to create my own KafkaProducer, but it’s so much easier to write this annotation!