ContainerSource

ContainerSource will start a container image which will generate events under certain situations and send messages to a sink URI. It also can be an easy way to support your own event sources in Knative. This guide shows how to configure ContainerSource as an event source for functions and summarizes guidelines for creating your own event source as a ContainerSource.

Prerequisites

• Install ko
• Set KO_DOCKER_REPO (e.g. gcr.io/[gcloud-project] or docker.io/<username>)
• Authenticated with your KO_DOCKER_REPO
• Install docker

Installation

The ContainerSource source type is enabled by default when you install Knative Eventing.

Example

This example shows how the heartbeats container sends events to the Event Display Service.

Preparing the heartbeats image

Knative event-sources has a sample of heartbeats event source. You could clone the source code by

git clone -b "v0.23.0" https://github.com/knative/eventing.git

And then build a heartbeats image and publish to your image repo with

ko publish ko://knative.dev/eventing/cmd/heartbeats

Creating a namespace

Create a new namespace called containersource-example by entering the following command:

kubectl create namespace containersource-example

Creating the Event Display Service

In order to verify ContainerSource is working, we will create a Event Display Service that dumps incoming messages to its log.

kubectl -n containersource-example apply -f - << EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: event-display
spec:
  replicas: 1
  selector:
    matchLabels: &labels
      app: event-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: event-display
spec:
  selector:
    app: event-display
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080
EOF

Creating the ContainerSource using the heartbeats image

In order to run the heartbeats container as an event source, you have to create a concrete ContainerSource with specific arguments and environment settings. Be sure to replace heartbeats_image_uri with a valid uri for your heartbeats image you published in the previous step. Note that arguments and environment variables are set and will be passed to the container.

kubectl -n containersource-example apply -f - << EOF
apiVersion: sources.knative.dev/v1
kind: ContainerSource
metadata:
  name: test-heartbeats
spec:
  template:
    spec:
      containers:
        # This corresponds to a heartbeats image uri you build and publish in the previous step
        # e.g. gcr.io/[gcloud-project]/knative.dev/eventing/cmd/heartbeats
        - image: <heartbeats_image_uri>
          name: heartbeats
          args:
            - --period=1
          env:
            - name: POD_NAME
              value: "mypod"
            - name: POD_NAMESPACE
              value: "event-test"
  sink:
    ref:
      apiVersion: v1
      kind: Service
      name: event-display
EOF

Verify

View the logs for the event-display event consumer by entering the following command:

kubectl -n containersource-example logs -l app=event-display --tail=200

This returns the Attributes and Data of the events that the ContainerSource sent to the event-display Service:

☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.eventing.samples.heartbeat
  source: https://knative.dev/eventing/cmd/heartbeats/#event-test/mypod
  id: 2b72d7bf-c38f-4a98-a433-608fbcdd2596
  time: 2019-10-18T15:23:20.809775386Z
  contenttype: application/json
Extensions,
  beats: true
  heart: yes
  the: 42
Data,
  {
    "id": 2,
    "label": ""
  }

Cleanup

Delete the containersource-example namespace and all of its resources from your cluster by entering the following command:

kubectl delete namespace containersource-example

Reference Documentation

See the ContainerSource specification.

Contact

For any inquiries about this source, please reach out on to the Knative users group.