How to determine a Kafka consumer's offset
We have an issue where it appears that a Kafka consumer is not receiving messages published to a topic. (I say appears as I have not yet got to the bottom of this, and I could be wrong.)
I am using Spring for Apache Kafka and my consumer is actually a method annotated with @KafkaListener.
This issue is intermittent and I am having trouble recreating it.
Is there a way for me to look at the Kafka broker's logs, or any other tool to help me find out the offset for my consumer? I want concrete evidence that my consumer is receiving the message or not.
Answer
Take a look at the kafka-consumer-groups tool, which can be used to check offsets and lag of consumers (consumer has to be active at the time you run this command).
./kafka-consumer-groups --bootstrap-server 127.0.0.1:9092 --new-consumer --describe --group console-consumer-55936
GROUP TOPIC PARTITION CURRENT-OFFSET LOG-END-OFFSET LAG OWNER
console-consumer-55936 test 0 6 6 0 consumer-1_/192.168.0.83
console-consumer-55936 test 1 1 1 0 consumer-1_/192.168.0.83
console-consumer-55936 test 2 1 1 0 consumer-1_/192.168.0.83
console-consumer-55936 test 3 1 1 0 consumer-1_/192.168.0.83
console-consumer-55936 test 4 2 2 0 consumer-1_/192.168.0.83
console-consumer-55936 test 5 1 1 0 consumer-1_/192.168.0.83
console-consumer-55936 test 6 1 1 0 consumer-1_/192.168.0.83
console-consumer-55936 test 7 2 2 0 consumer-1_/192.168.0.83
console-consumer-55936 test 8 1 1 0 consumer-1_/192.168.0.83
This should allow you to track whether anything is actually being consumed or not.