Mutual Exclusive Cases

    This example is the same as the multiple branches example except that we are now going to rely on the Knative function to provide a soft mutual exclusivity guarantee.

    NOTE: this example must be deployed in the default namespace.

    Let’s first create the switcher and transformer services that we will use in our Parallel.

    1. apiVersion: serving.knative.dev/v1
    2. kind: Service
    3. metadata:
    4.   name: event-display
    5. spec:
    6.   template:
    7.     spec:
    8.       containers:
    9.         - image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/event_display

    The parallel.yaml file contains the specifications for creating the Parallel object.

    1. apiVersion: flows.knative.dev/v1
    2. kind: Parallel
    3. metadata:
    4.   name: me-odd-even-parallel
    5. spec:
    6.   channelTemplate:
    7.     apiVersion: messaging.knative.dev/v1
    8.     kind: InMemoryChannel
    9.   branches:
    10.     - filter:
    11.       subscriber:
    12.         ref:
    13.           apiVersion: serving.knative.dev/v1
    14.           kind: Service
    16.     - filter:
    17.         uri: "http://me-even-odd-switcher.default.svc.cluster.local/1"
    18.       subscriber:
    19.         ref:
    20.           apiVersion: serving.knative.dev/v1
    21.           kind: Service
    22.           name: me-odd-transformer
    23.   reply:
    24.     ref:
    25.       apiVersion: serving.knative.dev/v1
    26.       kind: Service
    27.       name: me-event-display
    1. kubectl create -f ./parallel.yaml
    1. kubectl create -f ./ping-source.yaml

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

    Let’s look at the me-event-display log:

    1. kubectl logs -l serving.knative.dev/service=me-event-display --tail=50 -c user-container
    3. ☁️  cloudevents.Event
    4. Validation: valid
    5. Context Attributes,
    6.   specversion: 1.0
    7.   type: dev.knative.sources.ping
    8.   id: 0b0db15c-9b36-4388-8eaa-8c23a9dc2707
    9.   time: 2020-03-03T21:30:00.0007292Z
    10.   datacontenttype: application/json; charset=utf-8
    11. Extensions,
    12.   knativehistory: me-odd-even-parallel-kn-parallel-kn-channel.default.svc.cluster.local; me-odd-even-parallel-kn-parallel-0-kn-channel.default.svc.cluster.local
    13.   traceparent: 00-e8b17109cd21d4fa66a86633b5a614c7-ba96d220fe13211c-00
    14. Data,
    15.   {
    16.     "message": "we are even!"
    17.   }
    18. ☁️  cloudevents.Event
    19. Validation: valid
    20. Context Attributes,
    21.   specversion: 1.0
    22.   type: dev.knative.sources.ping
    23.   source: /apis/v1/namespaces/default/pingsources/me-ping-source
    24.   id: 321170d1-dea7-4b18-9290-28adb1de089b
    25.   time: 2020-03-03T21:31:00.0007847Z
    26.   datacontenttype: application/json; charset=utf-8
    27. Extensions,
    28.   knativehistory: me-odd-even-parallel-kn-parallel-kn-channel.default.svc.cluster.local; me-odd-even-parallel-kn-parallel-1-kn-channel.default.svc.cluster.local
    29.   traceparent: 00-78d8b044d23c85789f0a13fd3679ac24-1d69ddde56d620c7-00
    30. Data,
    31.   {
    32.     "message": "this is odd!"