Sequence terminal

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

    For this example, we’ll assume you have set up an as well as Knative Serving (for our functions). The examples use default namespace, again, if you want to deploy to 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.

    Setup

    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.

    1. apiVersion: flows.knative.dev/v1
    2. kind: Sequence
    3. metadata:
    4.   name: sequence
    5. spec:
    6.   channelTemplate:
    7.     apiVersion: messaging.knative.dev/v1
    8.     kind: InMemoryChannel
    9.   steps:
    10.     - ref:
    11.         apiVersion: serving.knative.dev/v1
    12.         name: first
    13.     - ref:
    14.         apiVersion: serving.knative.dev/v1
    16.         name: second
    17.     - ref:
    18.         apiVersion: serving.knative.dev/v1
    19.         kind: Service
    20.         name: third

    Change default in the following command to create the Sequence in the namespace where you want the resources to be created:

    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/v1
    2. kind: PingSource
    3. metadata:
    4.   name: ping-source
    5. spec:
    6.   schedule: "*/2 * * * *"
    7.   contentType: "application/json"
    8.   data: '{"message": "Hello world!"}'
    9.   sink:
    10.       apiVersion: flows.knative.dev/v1
    11.       kind: Sequence
    1. kubectl -n default create -f ./ping-source.yaml

    You can now see the final output by inspecting the logs of the event-display pods. Note that since we set the PingSource to emit every 2 minutes, it might take some time for the events to show up in the logs.

    1. kubectl -n default logs -l serving.knative.dev/service=first -c user-container --tail=-1
    3. 2020/03/02 21:28:00 listening on 8080, appending " - Handled by 0" to events
    4. 2020/03/02 21:28:01 Received a new event:
    5. 2020/03/02 21:28:01 [2020-03-02T21:28:00.0010247Z] /apis/v1/namespaces/default/pingsources/ping-source dev.knative.sources.ping: &{Sequence:0 Message:Hello world!}
    6. 2020/03/02 21:28:01 Transform the event to:
    7. 2020/03/02 21:28:01 [2020-03-02T21:28:00.0010247Z] /apis/v1/namespaces/default/pingsources/ping-source dev.knative.sources.ping: &{Sequence:0 Message:Hello world! - Handled by 0}

    And you can see that the initial PingSource message ("Hello World!") has now been modified by the first step in the Sequence to include “ - Handled by 0”. Exciting :)

    Then we can look at the output of the second Step in the Sequence:

    1. kubectl -n default logs -l serving.knative.dev/service=second -c user-container --tail=-1
    3. 2020/03/02 21:28:02 listening on 8080, appending " - Handled by 1" to events
    4. 2020/03/02 21:28:02 Received a new event:
    5. 2020/03/02 21:28:02 [2020-03-02T21:28:00.0010247Z] /apis/v1/namespaces/default/pingsources/ping-source dev.knative.sources.ping: &{Sequence:0 Message:Hello world! - Handled by 0}
    6. 2020/03/02 21:28:02 Transform the event to:
    7. 2020/03/02 21:28:02 [2020-03-02T21:28:00.0010247Z] /apis/v1/namespaces/default/pingsources/ping-source dev.knative.sources.ping: &{Sequence:0 Message:Hello world! - Handled by 0 - Handled by 1}

    And as expected it’s now been handled by both the first and second Step as reflected by the Message being now: “Hello world! - Handled by 0 - Handled by 1”

    Then we can look at the output of the last Step in the :