What does an increasing records-lag-max indicate?

What does an increasing records-lag-max indicate?

• A. The partitions are increasing
• B. The replicas are failing
• C. The producer is slower than the consumer
• D. The consumer group is not keeping up with producers

Answer: (D)

records-lag-max shows how far the most-behind partition in a consumer group is from the latest data. It’s the largest difference between the log end offset (the latest message) and the consumer’s current offset across all partitions in the group. When this value increases, the backlog is growing because producers are getting ahead of what the consumers can process. In other words, the consumer group isn’t keeping up with the producers. If producers were slower than the consumers, the lag would shrink or stay flat, since the consumer would quickly catch up. The other options don’t describe the situation shown by a rising lag: a changing number of partitions isn’t what lag measures, and replica issues would show up differently (in-sync replica problems, not the ongoing backlog between producer and consumer).

records-lag-max shows how far the most-behind partition in a consumer group is from the latest data. It’s the largest difference between the log end offset (the latest message) and the consumer’s current offset across all partitions in the group. When this value increases, the backlog is growing because producers are getting ahead of what the consumers can process. In other words, the consumer group isn’t keeping up with the producers.

If producers were slower than the consumers, the lag would shrink or stay flat, since the consumer would quickly catch up. The other options don’t describe the situation shown by a rising lag: a changing number of partitions isn’t what lag measures, and replica issues would show up differently (in-sync replica problems, not the ongoing backlog between producer and consumer).