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README.md	rename-sandbox (#5652 )	2023-08-03 17:52:21 +00:00

README.md

Apache Kafka Channel Example

You can install and configure the Apache Kafka Channel as the default Channel configuration for Knative Eventing.

Prerequisites

A Kubernetes cluster with Knative Eventing, as well as the optional Broker and Kafka Channel components.

Creating a Kafka Channel

Create a Kafka Channel that contains the following YAML:

apiVersion: messaging.knative.dev/v1beta1
kind: KafkaChannel
metadata:
  name: my-kafka-channel
spec:
  numPartitions: 3
  replicationFactor: 1

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Specifying Kafka as the default Channel implementation

To configure Kafka Channel as the default channel configuration, modify the default-ch-webhook ConfigMap so that it contains the following YAML:

apiVersion: v1
kind: ConfigMap
metadata:
  name: default-ch-webhook
  namespace: knative-eventing
data:
  # Configuration for defaulting channels that do not specify CRD implementations.
  default-ch-config: |
    clusterDefault:
      apiVersion: messaging.knative.dev/v1beta1
      kind: KafkaChannel
      spec:
        numPartitions: 3
        replicationFactor: 1

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Creating an Apache Kafka channel

After KafkaChannel is set as the default Channel type, you can create a Kafka Channel by creating a generic Channel object that contains the following YAML:
```
apiVersion: messaging.knative.dev/v1
kind: Channel
metadata:
  name: testchannel-one
```
Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.
Verify that the Channel was created properly by checking that your Kafka cluster has a testchannel-one Topic. If you are using Strimzi, you can run the command:
```
kubectl -n kafka exec -it my-cluster-kafka-0 -- bin/kafka-topics.sh --bootstrap-server my-cluster-kafka-bootstrap:9092 --list
```
The output looks similar to the following:
```
...
__consumer_offsets
knative-messaging-kafka.default.testchannel-one
...
```
The Kafka Topic that is created by the Channel contains the name of the namespace, default in this example, followed by the name of the Channel.

Note: The topic of a Kafka Channel is an implementation detail and records from it should not be consumed from different applications.

Creating a Service and Trigger that use the Apache Kafka Broker

The following example uses a ApiServerSource to publish events to an existing Broker, and a Trigger that routes those events to a Knative Service.

Create a Knative Service:

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: broker-kafka-display
spec:
  template:
    spec:
      containers:
      - image: gcr.io/knative-releases/knative.dev/eventing/cmd/event_display

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Create a ServiceAccount, ClusterRole, and ClusterRoleBinding for the ApiServerSource:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: events-sa
  namespace: default

---

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: event-watcher
rules:
- apiGroups:
  - ""
  resources:
  - events
  verbs:
  - get
  - list
  - watch

---

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: k8s-ra-event-watcher
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: event-watcher
subjects:
- kind: ServiceAccount
  name: events-sa
  namespace: default

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Create an ApiServerSource that sends events to the default Broker:

apiVersion: sources.knative.dev/v1
kind: ApiServerSource
metadata:
  name: testevents-kafka-03
  namespace: default
spec:
  serviceAccountName: events-sa
  mode: Resource
  resources:
  - apiVersion: v1
    kind: Event
  sink:
    ref:
      apiVersion: eventing.knative.dev/v1
      kind: Broker
      name: default

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Create a Trigger that filters events from the Broker to the Service:

apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: testevents-trigger
  namespace: default
spec:
  broker: default
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: broker-kafka-display

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.
Verifying the Kafka Channel is working, by observing events in the log of the Service, by running the command:
```
kubectl logs --selector='serving.knative.dev/service=broker-kafka-display' -c user-container
```

Channel configuration

KafkaChannel provides various configuration options, such as:

Authentication
Encryption
Kafka Topic default values (number of partitions, replication factor, and retention time)
The brokers string for your Kafka connection

For detailed information on configuration options, see the KafkaChannel README.