kafkacat_debugging.md

Running kafkacat against Strimzi

Assumption is that you have Strimzi already running as my-cluster-kafka on the kafka namespace.

Deployment for kafkacat

Create a deployment with a recent kafkacat, like:

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    run: kafkacat
  name: kafkacat
spec:
  replicas: 1
  selector:
    matchLabels:
      run: kafkacat
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        run: kafkacat
    spec:
      containers:
      - image: confluentinc/cp-kafkacat
        name: kafkacat
        resources: {}
        command:
          - sh
          - -c
          - "exec tail -f /dev/null"
status: {}

Now k apply -f that file, and once the pod is ready, open a bash session, like:

k exec -it kafkacat-xxxxx-yyyyy -- bash

Reading Kafka Records with headers

On the pod you now run something like the following to see all data, including record headers on a given topic:

kafkacat -C -b my-cluster-kafka-bootstrap.kafka.svc.cluster.local:9092 -t knative-messaging-kafka.default.testchannel \
  -f '\nKey (%K bytes): %k
  Value (%S bytes): %s
  Timestamp: %T
  Partition: %p
  Offset: %o
  Headers: %h\n'

This launches kafkacat as a consumer (-C) against the Strimzi broker (-b) with a given topic (-t), where all records on the topic are rendered, including its headers.

This might give you a message like:

...
Key (-1 bytes): 
  Value (1111 bytes): {"apiVersion":"v1","count":1,"eventTime":null,"firstTimestamp":"2021-05-19T07:01:04Z","involvedObject":{"apiVersion":"v1","fieldPath":"spec.containers{curlcli}","kind":"Pod","name":"curlcli","namespace":"default","resourceVersion":"272474","uid":"f0e510fa-2740-4a2e-8eb5-da02826e4fae"},"kind":"Event","lastTimestamp":"2021-05-19T07:01:04Z","message":"Created container curlcli","metadata":{"creationTimestamp":"2021-05-19T07:01:04Z","managedFields":[{"apiVersion":"v1","fieldsType":"FieldsV1","fieldsV1":{"f:count":{},"f:firstTimestamp":{},"f:involvedObject":{"f:apiVersion":{},"f:fieldPath":{},"f:kind":{},"f:name":{},"f:namespace":{},"f:resourceVersion":{},"f:uid":{}},"f:lastTimestamp":{},"f:message":{},"f:reason":{},"f:source":{"f:component":{},"f:host":{}},"f:type":{}},"manager":"kubelet","operation":"Update","time":"2021-05-19T07:01:04Z"}],"name":"curlcli.168065ae11d6cbd2","namespace":"default","resourceVersion":"272480","uid":"c390edf8-7146-4b2c-a990-bf9385e055be"},"reason":"Created","reportingComponent":"","reportingInstance":"","source":{"component":"kubelet","host":"minikube"},"type":"Normal"}
  Timestamp: 1621407664155
  Partition: 1
  Offset: 82
  Headers: ce_time=2021-05-19T07:01:04.155157925Z,ce_id=1daca56a-d50c-472d-b9c8-e9e77435e280,ce_subject=/apis/v1/namespaces/default/events/curlcli.168065ae11d6cbd2,ce_name=curlcli.168065ae11d6cbd2,ce_specversion=1.0,ce_kind=Event,ce_namespace=default,ce_source=https://10.96.0.1:443,ce_type=dev.knative.apiserver.resource.add,content-type=application/json,traceparent=00-c1df3d88293179613b385eb838115c41-d2a3441d93e0f4d1-00
% Reached end of topic knative-messaging-kafka.default.testchannel [1] at offset 83

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