What do we mean by 'commit' data in Kafka broker?

Question

In a Kafka cluster containing N brokers , for Topic T against a partition, producers publish data to Leader broker. By the term 'commit' in Kafka terminology , does it mean the data is committed in Leader broker or the data is committed to the Leader broker and also to the corresponding Followers available in the ISR list.

Answer 1

This is controlled by the producer configuration setting called ack:

• acks=0 If set to zero then the producer will not wait for any acknowledgment from the server at all. The record will be immediately added to the socket buffer and considered sent. No guarantee can be made that the server has received the record in this case, and the retries configuration will not take effect (as the client won't generally know of any failures). The offset given back for each record will always be set to -1.

• acks=1 (default) This will mean the leader will write the record to its local log but will respond without awaiting full acknowledgement from all followers. In this case should the leader fail immediately after acknowledging the record but before the followers have replicated it then the record will be lost.

• acks=all This means the leader will wait for the full set of in-sync replicas to acknowledge the record. This guarantees that the record will not be lost as long as at least one in-sync replica remains alive. This is the strongest available guarantee.