tl;dr Make sure that key.converter.schema.registry.url and value.converter.schema.registry.url are specified, and that there are no trailing whitespaces. I’ve been building on previous work I’ve done with Oracle GoldenGate and Kafka Connect, looking at how to have the change records from the Oracle database come through to Kafka in Avro format rather than the default JSON that the sample configuration gives. Simply changing the Kafka Connect OGG configuration file (confluent.properties) from value.converter=org.apache.kafka.connect.json.JsonConverter key.