Kafka-consumer. commitSync vs commitAsync

Question

The quote from https://www.safaribooksonline.com/library/view/kafka-the-definitive/9781491936153/ch04.html#callout_kafka_consumers__reading_data_from_kafka_CO2-1

Answer 1

commitAync will not retry because if it retries it will make a mess.

Imagine that you are trying to commit offset 20 (async), and it did not commit (failed), and then the next poll block tries to commit the offset 40 (async), and it succeeded.

Now, commit offset 20 is still waiting to commit, if it reties and succeed it will make a mess.

The mess is that the committed offset should be 40 not 20.