[Kafka] Exactly once delivery

Among the various configuration settings that you set for your producers and consumers, there is a specific set that is very important if you care about EOD (Exactly Once Delivery).

Producers:

• enable.idempotence = true
• max.in.flight.requests.per.connection <= 5
• retries > 0
• acks = "all"

Consumers:

• isolation.level = "read_committed"

The consumer configuration is NOT strictly necessary, since messages that are not part of a transaction are not affected by it, but in case your producer would send messages as part of a transaction, you might want to avoid reading aborted ones.