Apache Kafka Channel Example

• Ensure that you meet the prerequisites listed in the Apache Kafka overview.
• A Kubernetes cluster with .

Creating a KafkaChannel channel CRD

Create a new object by configuring the YAML file as follows:

To configure the usage of the KafkaChannel CRD as the , edit the default-ch-webhook ConfigMap as follows:

cat <<-EOF | kubectl apply -f -
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: default-ch-webhook
  namespace: knative-eventing
  # Configuration for defaulting channels that do not specify CRD implementations.
  default-ch-config: |
    clusterDefault:
      apiVersion: messaging.knative.dev/v1beta1
      kind: KafkaChannel
      spec:
        replicationFactor: 1
EOF

Creating an Apache Kafka channel using the default channel configuration

Now that KafkaChannel is set as the default channel configuration, you can use the channels.messaging.knative.dev CRD to create a new Apache Kafka channel, using the generic Channel:

cat <<-EOF | kubectl apply -f -
---
apiVersion: messaging.knative.dev/v1
kind: Channel
metadata:
  name: testchannel-one
EOF

Check Kafka for a testchannel topic. With Strimzi this can be done by using the command:

kubectl -n kafka exec -it my-cluster-kafka-0 -- bin/kafka-topics.sh --zookeeper localhost:2181 --list

The Apache Kafka topic that is created by the channel implementation is prefixed with knative-messaging-kafka. This indicates it is an Apache Kafka channel from Knative. It contains the name of the namespace, default in this example, followed by the actual name of the channel.

To setup a broker that will use the new default Kafka channels, you must create a new default broker, using the command:

apiVersion: eventing.knative.dev/v1
metadata:
 name: default
EOF

This will give you two pods, such as:

default-broker-filter-64658fc79f-nf596                            1/1     Running     0          15m
default-broker-ingress-ff79755b6-vj9jt                            1/1     Running     0          15m

Inside the Apache Kafka cluster you should see two new topics, such as:

...
knative-messaging-kafka.default.default-kn2-ingress
knative-messaging-kafka.default.default-kn2-trigger
...

Creating a service and trigger to use the Apache Kafka broker

1. Install ksvc, using the command:

2. Install a source that publishes to the default broker

   kubectl apply -f 020-k8s-events.yaml

3. Create a trigger that routes the events to the ksvc:

   kubectl apply -f 030-trigger.yaml

Now that your Eventing cluster is configured for Apache Kafka, you can verify your configuration with the following options.

kubectl logs --selector='serving.knative.dev/service=broker-kafka-display' -c user-container