What is deduplication in Kafka?

Deduplication in Kafka is a mechanism to prevent processing duplicate messages, which can occur due to resending by the producer or network failures. In Kafka, this is implemented through producer idempotence and the use of unique message identifiers (e.g., sequence number).

An idempotent producer assigns a unique identifier to each message, and the Kafka broker guarantees that messages with the same identifier will be written to the topic only once, ignoring duplicates. This is especially important for ensuring data accuracy and consistency in systems where message resending is possible.

Example of configuring an idempotent producer in Go using the sarama library:

config := sarama.NewConfig()
config.Producer.Idempotent = true
producer, err := sarama.NewSyncProducer(brokers, config)
if err != nil {
    panic(err)
}
// now the producer will automatically deduplicate messages

Thus, deduplication in Kafka helps avoid data duplication during repeated message sending attempts.