Multiple Cases

We are going to create a Parallel with two branches:

• the first branch accepts events with a time that is is even
• the second branch accepts events with a time that is is odd

The events produced by each branch are then sent to the event-display service.

Prerequisites

Please refer to the sample overview for the prerequisites.

Create the Knative Services

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

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: even-filter
spec:
  template:
    spec:
      containers:
      - image: villardl/filter-nodejs:0.1
        env:
        - name: FILTER
          value: |
            Math.round(Date.parse(event.time) / 60000) % 2 === 0
---
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: odd-filter
spec:
  template:
    spec:
      containers:
      - image: villardl/filter-nodejs:0.1
        env:
        - name: FILTER
          value: |
            Math.round(Date.parse(event.time) / 60000) % 2 !== 0
---
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: even-transformer
spec:
  template:
    spec:
      containers:
      - image: villardl/transformer-nodejs
        env:
        - name: TRANSFORMER
          value: |
            ({"message": "we are even!"})
---
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: odd-transformer
spec:
  template:
    spec:
      containers:
      - image: villardl/transformer-nodejs:0.1
        env:
        - name: TRANSFORMER
          value: |
            ({"message": "this is odd!"})
.

kubectl create -f ./filters.yaml -f ./transformers.yaml

Create the Service displaying the events created by Sequence

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

Change default below to create the Sequence in the Namespace where you want your resources to be created.

kubectl -n default create -f ./event-display.yaml

Create the Parallel

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

apiVersion: flows.knative.dev/v1beta1
kind: Parallel
metadata:
  name: odd-even-parallel
spec:
  channelTemplate:
    apiVersion: messaging.knative.dev/v1beta1
    kind: InMemoryChannel
  branches:
    - filter:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: even-filter
      subscriber:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: even-transformer
    - filter:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: odd-filter
      subscriber:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: odd-transformer
  reply:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: event-display

kubectl create -f ./parallel.yaml

Create the PingSource targeting the Parallel

This will create a PingSource which will send a CloudEvent with {"message": "Even or odd?"} as the data payload every minute.

apiVersion: sources.knative.dev/v1alpha2
kind: PingSource
metadata:
  name: ping-source
spec:
  schedule: "*/1 * * * *"
  data: '{"message": "Even or odd?"}'
  sink:
    ref:
      apiVersion: flows.knative.dev/v1alpha2
      kind: Parallel
      name: odd-even-parallel

kubectl create -f ./ping-source.yaml

Inspecting the results

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 minute, it might take some time for the events to show up in the logs.

Let’s look at the event-display log:

kubectl logs -l serving.knative.dev/service=event-display --tail=30 -c user-container
☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.sources.ping
  source: /apis/v1/namespaces/default/pingsources/ping-source
  id: 015a4cf4-8a43-44a9-8702-3d4171d27ba5
  time: 2020-03-03T21:24:00.0007254Z
  datacontenttype: application/json; charset=utf-8
Extensions,
  knativehistory: odd-even-parallel-kn-parallel-kn-channel.default.svc.cluster.local; odd-even-parallel-kn-parallel-0-kn-channel.default.svc.cluster.local
  traceparent: 00-41a139bf073f3cfcba7bb7ce7f1488fc-68a891ace985221a-00
Data,
  {
    "message": "we are even!"
  }
☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.sources.ping
  source: /apis/v1/namespaces/default/pingsources/ping-source
  id: 52e6b097-f914-4b5a-8539-165650e85bcd
  time: 2020-03-03T21:23:00.0004662Z
  datacontenttype: application/json; charset=utf-8
Extensions,
  knativehistory: odd-even-parallel-kn-parallel-kn-channel.default.svc.cluster.local; odd-even-parallel-kn-parallel-1-kn-channel.default.svc.cluster.local
  traceparent: 00-58d371410d7daf2033be226860b4ee5d-05d686ee90c3226f-00
Data,
  {
    "message": "this is odd!"
  }