Consumer lag monitoring in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is consumer lag in Kafka?

Consumer lag is the difference between the latest message offset in a Kafka partition and the offset of the last message processed by a consumer. It shows how far behind the consumer is.

beginner

Why is monitoring consumer lag important?

Monitoring consumer lag helps ensure consumers are processing messages in a timely manner. High lag means delays or problems in processing, which can cause stale data or system issues.

beginner

Name a common tool used to monitor Kafka consumer lag.

Kafka's built-in tool 'kafka-consumer-groups.sh' is commonly used to check consumer lag by showing current offsets and lag per consumer group.

intermediate

How can you check consumer lag using kafka-consumer-groups.sh?

Run: kafka-consumer-groups.sh --bootstrap-server <broker> --describe --group . It shows partition offsets, current consumer offsets, and lag.

beginner

What does a lag of zero mean for a Kafka consumer?

A lag of zero means the consumer has processed all available messages and is up to date with the latest data in the partition.

What does consumer lag measure in Kafka?

A Number of partitions in a topic

B Number of consumers in a group

C Size of Kafka topic

D Difference between latest message offset and consumer's last processed offset

Consumer lag measures how far behind a consumer is by comparing the latest offset with the consumer's last processed offset.

Which Kafka tool helps you check consumer lag?

A kafka-consumer-groups.sh

B kafka-topics.sh

C kafka-producer-perf-test.sh

D kafka-configs.sh

The kafka-consumer-groups.sh tool shows consumer group offsets and lag.

What does a high consumer lag indicate?

A Consumer is processing messages slowly or stuck

B Consumer is up to date

C Topic has no messages

D Consumer group has too many members

High lag means the consumer is behind and not processing messages fast enough.

Which command option shows detailed consumer group info including lag?

A --list

B --delete

C --describe

D --help

The --describe option shows detailed info including lag for consumer groups.

If consumer lag is zero, what does it mean?

A Topic is empty

B Consumer is caught up with all messages

C Consumer is offline

D Consumer group is new

Zero lag means the consumer has processed all messages and is current.

Explain what consumer lag is and why it matters in Kafka.

Think about how far behind a consumer is and what happens if it falls behind.

Describe how to check consumer lag using Kafka command-line tools.

Focus on the command and what information it shows.