Exactly Once Semantics

You can provide a listener container with a KafkaAwareTransactionManager instance. When so configured, the container starts a transaction before invoking the listener. Any KafkaTemplate operations performed by the listener participate in the transaction. If the listener successfully processes the record (or multiple records, when using a BatchMessageListener), the container sends the offset(s) to the transaction by using producer.sendOffsetsToTransaction()), before the transaction manager commits the transaction. If the listener throws an exception, the transaction is rolled back and the consumer is repositioned so that the rolled-back record(s) can be retrieved on the next poll. See After-rollback Processor for more information and for handling records that repeatedly fail.

Using transactions enables Exactly Once Semantics (EOS).

This means that, for a read → process → write sequence, it is guaranteed that the sequence is completed exactly once. (The read and process have at least once semantics).

Spring for Apache Kafka version 3.0 and later only supports EOSMode.V2:

With mode V2, it is not necessary to have a producer for each group.id/topic/partition because consumer metadata is sent along with the offsets to the transaction and the broker can determine if the producer is fenced using that information instead.

Refer to KIP-447 for more information.

V2 was previously BETA; the EOSMode has been changed to align the framework with KIP-732.