Kafka

• https://stackoverflow.com/questions/29647656/effective-strategy-to-avoid-duplicate-messages-in-apache-kafka-consumer
• http://bytecontinnum.com/2016/06/exactly-kafka-storm-integration/

According this :

 Starting with Flink 1.4.0, both the Pravega and Kafka 0.11 producers provide exactly-once semantics; 
 Kafka introduced transactions for the first time in Kafka 0.11, which is what made the 
 Kafka exactly-once producer possible in Flink.

it means: that only from Kafka 0.11 and Flink 1.4.0 and Pravega - Exactly once supported