Consumer Lag for transactional message

[hgdhot]

Description

when set enable.auto.commit as false, manually commit the received messages, the consumer lag keeps to be 1 , it seems like the transaction control message is not commited, because of the application didn't receive the control message, how can the application commit it?

How to reproduce

• Produce message to test topic via transaction;
• consume from the test topic, using enable.auto.commit=false;
• commit received messages manually;

Checklist

• [x] librdkafka version (release number or git tag): V1.6.0.3
• [x] Apache Kafka version: 2.2.0
• [x] librdkafka client configuration: enable.auto.commit=false