This article is based on Knative version V0.23

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Start using Knative Eventing

Create a Knative Eventing Namespace

kubectl create namespace event-example
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Adding a Broker

The broker routes events to different event receivers or consumers.

Add a broker called default with the following command:

kubectl create -f - <<EOF apiVersion: eventing.knative.dev/v1 kind: broker metadata: name: default namespace: event-example EOF
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Confirm that the broker is running correctly:

kubectl -n event-example get broker default
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Ensure that the Ready state is True:

NAME      URL                                                                              AGE   READY   REASON
default   http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default   45s   True
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Create event consumers

Here we create two event consumers, Hello -display and goodbye-display, to demonstrate how the event producer can be configured to target a specific consumer.

Deploy the Hello-display consumer to the cluster with the following command:

kubectl -n event-example apply -f - << EOF apiVersion: apps/v1 kind: Deployment metadata: name: hello-display spec: replicas: 1 selector: matchLabels: &labels app: hello-display template: metadata: labels: *labels spec: containers: - name: event-display image: gcr.io/knative-releases/knative.dev/eventing/cmd/event_display --- kind: Service apiVersion: v1 metadata: name: hello-display spec: selector: app: hello-display ports: - protocol: TCP port: 80 targetPort: 8080 EOF
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Deploy the inward-display consumer to the cluster with the following command:

kubectl -n event-example apply -f - << EOF apiVersion: apps/v1 kind: Deployment metadata: name: goodbye-display spec: replicas: 1 selector: matchLabels: &labels app: goodbye-display template: metadata: labels: *labels spec: containers: - name: event-display # Source code: https://github.com/knative/eventing/tree/main/cmd/event_display image: gcr.io/knative-releases/knative.dev/eventing/cmd/event_display --- kind: Service apiVersion: v1 metadata: name: goodbye-display spec: selector: app: goodbye-display ports: - protocol: TCP port: 80 targetPort: 8080 EOF
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Verify that the consumer is working properly with the following command:

kubectl -n event-example get deployments hello-display goodbye-display
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The above command lists our deployed hello-display and indone-display consumers:

NAME              READY   UP-TO-DATE   AVAILABLE   AGE
hello-display     1/1     1            1           2m1s
goodbye-display   1/1     1            1           47s
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The number of copies in the READY column should match the number in the AVAILABLE column.

Create triggers

Triggers define the events that each event consumer receives. Brokers uses Triggers to send the event to the correct consumer. Each trigger can specify a filter that can select related events based on the Cloud Event Context Attribute.

Create a trigger:

kubectl -n event-example apply -f - << EOF apiVersion: eventing.knative.dev/v1 kind: Trigger metadata: name: hello-display spec: broker: default filter: attributes: type: greeting subscriber: ref: apiVersion: v1 kind: Service name: hello-display EOF
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This command creates a trigger to send all events of type greeting to an event consumer named hello-display.

Create a second consumer:

kubectl -n event-example apply -f - << EOF apiVersion: eventing.knative.dev/v1 kind: Trigger metadata: name: goodbye-display spec: broker: default filter: attributes: source: sendoff subscriber: ref: apiVersion: v1 kind: Service name: goodbye-display EOF
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This command creates a trigger that sends all events with source Sendoff to an event consumer named indone-display.

Confirm that the trigger works properly:

kubectl -n event-example get triggers
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This command returns two triggers just created:

NAME              BROKER    SUBSCRIBER_URI                                            AGE     READY   REASON
goodbye-display   default   http://goodbye-display.event-example.svc.cluster.local/   44s     True
hello-display     default   http://hello-display.event-example.svc.cluster.local/     4m47s   True
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If triggers are configured correctly, it is Ready and points to the correct broker and SUBSCRIBER_URI.

Create a Pod as the event producer

We use the curl command to manually send individual events to the broker as HTTP requests and demonstrate how these events are correctly received by event consumers.

You can only access the broker from within the cluster where you have Knative Eventing installed, so you must create a POD within the cluster to execute the curl command as an event producer.

Create a POD with the following command:

kubectl -n event-example apply -f - << EOF apiVersion: v1 kind: Pod metadata: labels: run: curl name: curl spec: containers: # This could be any image that we can SSH into and has curl. - image: radial/busyboxplus:curl imagePullPolicy: IfNotPresent name: curl resources: {} stdin: true terminationMessagePath: /dev/termination-log terminationMessagePolicy: File tty: true EOF
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Send events to the broker

Go to the container you just created:

kubectl -n event-example attach curl -it
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Here we build three requests to show the various types of events that can be sent:

Build an event of type greeting:

curl -v "http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default" \
  -X POST \
  -H "Ce-Id: say-hello" \
  -H "Ce - Specversion: 1.0" \
  -H "Ce-Type: greeting" \
  -H "Ce-Source: not-sendoff" \
  -H "Content-Type: application/json" \
  -d '{"msg":"Hello Knative!" } '
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When the broker receives the event, hell-display is activated and sent to the event consumer. If the event is received, you will receive a response like 202 Accepted:

< HTTP/1.1 202 Accepted
< Date: Wed, 02 Jun 2021 08:35:12 GMT
< Content-Length: 0
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Build an event with source as Sendoff:

curl -v "http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default" \
  -X POST \
  -H "Ce-Id: say-goodbye" \
  -H "Ce - Specversion: 1.0" \
  -H "Ce-Type: not-greeting" \
  -H "Ce-Source: sendoff" \
  -H "Content-Type: application/json" \
  -d '{"msg":"Goodbye Knative!" } '
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When the broker receives the event, inward-display is activated and the event is sent to the event consumer. If the event is received, you will receive a response like 202 Accepted:

< HTTP/1.1 202 Accepted
< Date: Wed, 02 Jun 2021 08:42:02 GMT
< Content-Length: 0
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Build an event containing type greeting and source sendoff:

curl -v "http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default" \
  -X POST \
  -H "Ce-Id: say-hello-goodbye" \
  -H "Ce - Specversion: 1.0" \
  -H "Ce-Type: greeting" \
  -H "Ce-Source: sendoff" \
  -H "Content-Type: application/json" \
  -d '{"msg":"Hello Knative! Goodbye Knative!" } '
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When the broker receives the event, both helium-display and inward-display are activated and send the event to the corresponding event consumer. If the event is received, you will receive a response like 202 Accepted:

< HTTP/1.1 202 Accepted
< Date: Wed, 02 Jun 2021 08:45:16 GMT
< Content-Length: 0
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Run the exit command to exit the container.

At this point we send two events to the Hello-display event consumer and two to the indone-display event consumer. Let’s make sure these events are received correctly.

Acknowledge event reception

Verify that the event was received by the correct subscriber.

To view logs of the Hello-display event consumer:

kubectl -n event-example logs -l app=hello-display --tail=100
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You can see the Attributes and Data of the event sent to hello-display:

☁️ cloudevents.Event Context Attributes, specVersion: 1.0 type: greeting source: not-sendoff ID: say-hello datacontenttype: application/json Extensions, knativearrivaltime: 2021-06-02t08:35:12.137155445z Data, {" MSG ": "Hello Knative!" } ☁️ cloudevents.Event Context Attributes, specversion: 1.0 type: greeting source: Sendoff ID: say-hello-goodbye datacontenttype: application/json Extensions, knativearrivaltime: 2021-06-02t08:45:16.087732995z Data, {" MSG ": "Hello Knative! Goodbye Knative!" }Copy the code

To view the log for the indone-display event consumer:

kubectl -n event-example logs -l app=goodbye-display --tail=100
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You can see the Attributes and Data for the event sent to indone-display:

☁️ cloudevents.Event Context Attributes, specVersion: 1.0 type: not-greeting source: Sendoff ID: say-goodbye datacontenttype: application/json Extensions, knativearrivaltime: 2021-06-02t08:42:02.227918434z Data, {" MSG ": "Goodbye Knative!" } ☁️ cloudevents.Event Context Attributes, specversion: 1.0 type: greeting source: Sendoff ID: say-hello-goodbye datacontenttype: application/json Extensions, knativearrivaltime: 2021-06-02t08:45:16.087732995z Data, {" MSG ": "Hello Knative! Goodbye Knative!" }Copy the code

The resources

Knative. Dev/docs/eventi…

Knative Practice: Use brokers and triggers

Start using Knative Eventing

Create a Knative Eventing Namespace

Adding a Broker

Create event consumers

Create triggers

Create a Pod as the event producer

Send events to the broker

Acknowledge event reception

The resources

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