Apache 3.x now supports exactly once delivery.  The attached PR provides support but requires the minimum version that the connector will support to be 3.0. This will be a breaking change so this should be addressed with the work for version 2.0 of the connector

Links:

• Exactly-Once Semantics Are Possible: Here’s How Kafka Does It
• Enabling Exactly-Once in Kafka Streams
• Exactly Once Delivery and Transactional Messaging in Kafka. The definitive design.
• KIP-618: Exactly-Once Support for Source Connectors