How to reset offset and re-consume a topic for an existing consumer group using Confluent Kafka JS?

[ArekCzarnikRTL]

I’m using the Confluent Kafka JS client and I’d like to programmatically re-consume a topic from the beginning with an already existing consumer group.

More specifically:
How can I reset the offset within my code so that the consumer starts reading the topic from the beginning again?
I’ve seen references to seek(), but I’m unsure how to use it properly in this context.
Do I need to fetch the partition metadata manually first? And what’s the recommended way to do this cleanly?

Any code example or guidance would be greatly appreciated.

Thanks in advance!

[aferrando-tid]

We do this in a couple of our applications without much trouble.

We use the node-rdkafka consumers, and the admin client from KafkaJS, so the semantics might vary a bit there.

The thing is, you don't want to actually reset your consumer group itself, because that requires the consumer group to be empty and is a mess depending on how loaded your cluster is, how many instances of the same consumer you have etc.

So using seek is quite the better option

Prerequisite: consumer group must be stable (consumers able to receive new messages)

Fetch topic partition offset data using admin client (you mostly want the low offset here)

Fetch current assignments

pause consumer

seek to lowest offset using the data from the admin call for the current assignments.

resume consumer

consumer starts reading from the new offset