Hi Marco, The documentation kind of suggestion this is the cause: > https://nightlies.apache.org/flink/flink-docs-release-1.12/dev/connectors/kafka.html > > However, I think the documentation could benefit with a few examples and > scenarios that can ill-considered configurations. >
Matthias already provided a nice explanation of the usage of Kafka transactions in EXACTLY_ONCE mode (thanks Matthias!), so I just want to comment on the docs: I think you are right that this gotcha could be pointed out explicitly. In fact, it is pointed out in the 1.14 docs [1] (last sentence of the EXACTLY_ONCE description), so others obviously thought the same. If you feel it should still be added to the 1.12 docs, feel free to open a Jira ticket or even provide a PR yourself :-) [2]. Best, Nico [1] https://nightlies.apache.org/flink/flink-docs-release-1.14/docs/connectors/datastream/kafka/#fault-tolerance [2] https://flink.apache.org/contributing/how-to-contribute.html >