Using Sequence with Broker and Trigger

    For this example, we’ll assume you have set up an InMemoryChannel as well as Knative Serving (for our functions). The examples use default namespace, again, if your broker lives in another Namespace, you will need to modify the examples to reflect this.

    If you want to use different type of Channel, you will have to modify the Sequence.Spec.ChannelTemplate to create the appropriate Channel resources.

    The functions used in these examples live in https://github.com/knative/eventing-contrib/blob/master/cmd/appender/main.go.

    Setup

    The easiest way to create a Broker is to annotate your namespace:

    Create the Knative Services

    1. apiVersion: serving.knative.dev/v1
    2. kind: Service
    3. metadata:
    4.   name: first
    5. spec:
    6.   template:
    7.     spec:
    8.       containers:
    9.         - image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
    10.           env:
    11.             - name: MESSAGE
    12.               value: " - Handled by 0"
    14. ---
    15. apiVersion: serving.knative.dev/v1
    16. kind: Service
    17. metadata:
    18.   name: second
    19. spec:
    20.   template:
    21.     spec:
    22.       containers:
    23.         - image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
    24.           env:
    25.             - name: MESSAGE
    26.               value: " - Handled by 1"
    27. ---
    28. apiVersion: serving.knative.dev/v1
    29. kind: Service
    30. metadata:
    31.   name: third
    32. spec:
    33.   template:
    34.       containers:
    35.         - image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
    36.           env:
    37.             - name: MESSAGE
    38.               value: " - Handled by 2"
    1. kubectl -n default create -f ./steps.yaml

    The sequence.yaml file contains the specifications for creating the Sequence. If you are using a different type of Channel, you need to change the spec.channelTemplate to point to your desired Channel.

    Also, change the spec.reply.name to point to your Broker

    1. apiVersion: flows.knative.dev/v1beta1
    2. kind: Sequence
    3. metadata:
    4.   name: sequence
    5. spec:
    6.   channelTemplate:
    7.     apiVersion: messaging.knative.dev/v1beta1
    8.     kind: InMemoryChannel
    9.   steps:
    10.     - ref:
    11.         apiVersion: serving.knative.dev/v1
    12.         kind: Service
    13.         name: first
    14.     - ref:
    15.         apiVersion: serving.knative.dev/v1
    16.         kind: Service
    17.         name: second
    18.     - ref:
    19.         apiVersion: serving.knative.dev/v1
    20.         kind: Service
    21.         name: third
    22.   reply:
    23.     ref:
    24.       kind: Broker
    25.       apiVersion: eventing.knative.dev/v1beta1
    26.       name: default

    Change default below to create the Sequence in the Namespace where you have configured your Broker.

    Create the PingSource targeting the Broker

    This will create a PingSource which will send a CloudEvent with {“message”: “Hello world!”} as the data payload every 2 minutes.

    1. apiVersion: sources.knative.dev/v1alpha2
    2. kind: PingSource
    3. metadata:
    4.   name: ping-source
    5. spec:
    6.   schedule: "*/2 * * * *"
    7.   jsonData: '{"message": "Hello world!"}'
    8.   sink:
    9.       apiVersion: eventing.knative.dev/v1beta1
    10.       kind: Broker
    11.       name: default

    Here, if you are using different type of Channel, you need to change the spec.channelTemplate to point to your desired Channel. Also, change the spec.reply.name to point to your Broker

    1. kubectl -n default create -f ./ping-source.yaml
    1. apiVersion: eventing.knative.dev/v1beta1
    2. kind: Trigger
    3. metadata:
    4.   name: sequence-trigger
    5. spec:
    6.   filter:
    7.     attributes:
    8.       type: dev.knative.sources.ping
    9.   subscriber:
    10.     ref:
    11.       apiVersion: flows.knative.dev/v1beta1
    12.       kind: Sequence
    13.       name: sequence

    Change default below to create the Sequence in the Namespace where you have configured your Broker.

    Create the Service and Trigger displaying the events created by Sequence

    1. apiVersion: serving.knative.dev/v1
    2. kind: Service
    3. metadata:
    4.   name: sequence-display
    5. spec:
    6.   template:
    7.     spec:
    8.       containers:
    9.         - image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
    10. ---
    11. apiVersion: eventing.knative.dev/v1alpha1
    12. kind: Trigger
    13. metadata:
    14.   name: display-trigger
    15. spec:
    16.   filter:
    17.     attributes:
    18.       type: samples.http.mod3
    19.   subscriber:
    20.     ref:
    21.       apiVersion: serving.knative.dev/v1
    22.       kind: Service
    23.       name: sequence-display
    24. ---

    Change default below to create the Service and Trigger in the Namespace where you have configured your Broker.

    1. kubectl -n default create -f ./display-trigger.yaml

    You can now see the final output by inspecting the logs of the event-display pods.

      Then look at the logs for the event-display pod:

      And you can see that the initial PingSource message has been appended to it by each of the steps in the Sequence.