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Troubleshoot Knative Eventing with Kafka: Useful Commands

Debug Knative Eventing with Kafka using kn and kubectl commands. Inspect services, revisions, triggers, Kafka sources, and event delivery.

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Useful commands

  1. Display list of knative services

    kn services list

  2. Display config for specific service

    kn service describe --verbose <SERVICE_NAME>

  3. List all revisions

    kn revisions list

  4. Display triggers

    kn triggers list
kubectl get triggers

  5. Display kafka sources

    kubectl get kafkasource

  6. Run Kafka Producer container

    kubectl -n kafka run kafka-producer -ti --image=strimzi/kafka:0.14.0-kafka-2.3.0 --rm=true --restart=Never -- bash

  7. List kafka topics

    bin/kafka-topics.sh --bootstrap-server <BOOTSTRAP_SERVER_HOST> --list

  8. List messages produced to a specific topic

    bin/kafka-console-consumer.sh --bootstrap-server <BOOTSTRAP_SERVER_HOST> --topic <TOPIC_NAME> --from-beginning

  9. List messages from knative broker topic

    bin/kafka-console-consumer.sh --bootstrap-server <BOOTSTRAP_SERVER_HOST> --topic knative-broker-default-default --from-beginning

  10. List all consumer groups in Kafka

    bin/kafka-consumer-groups.sh  --list --bootstrap-server <BOOTSTRAP_SERVER_HOST>

  11. Display all consumer groups with details

    bin/kafka-consumer-groups.sh --describe --all-groups --bootstrap-server <BOOTSTRAP_SERVER_HOST>

  12. List offset with lag for each knative topic

    bin/kafka-consumer-groups.sh --describe --group knative-group --bootstrap-server <BOOTSTRAP_SERVER_HOST>

  13. Count the lag of the offset from previous group command

    bin/kafka-consumer-groups.sh --describe --group knative-group --bootstrap-server <BOOTSTRAP_SERVER_HOST> | awk 'NR>1 {sum += $6} END {print sum}'

Debugging flow

  1. Check if your source topic is working:

    • Run kafka-producer (6)
    • Produce kafka message to the source topic
    • Check if message arrived to the topic (8)

  2. Check if the Trigger is properly connected/filtered

    • Check status of triggers (4)
    • Check filter defined in yaml file and check headers in the consumer service if it is matching the query

  3. Check if your events are copied into broker topic

    • Run kafka-producer (6)
    • Produce kafka message to the source topic
    • Check if message arrived to the topic (8) - if default topic name is used, the name is: knative-broker-default-default

  4. Check if pods in knative-eventing namespace do not raise errors e.g. kafka-broker-dispatcher

Useful resources/tools

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