Search

Chapter 2. Event sources

download PDF

2.1. Event sources

A Knative event source can be any Kubernetes object that generates or imports cloud events, and relays those events to another endpoint, known as a sink. Sourcing events is critical to developing a distributed system that reacts to events.

You can create and manage Knative event sources by using the Developer perspective in the OpenShift Container Platform web console, the Knative (kn) CLI, or by applying YAML files.

Currently, OpenShift Serverless supports the following event source types:

API server source
Brings Kubernetes API server events into Knative. The API server source sends a new event each time a Kubernetes resource is created, updated or deleted.
Ping source
Produces events with a fixed payload on a specified cron schedule.
Kafka event source
Connects an Apache Kafka cluster to a sink as an event source.

You can also create a custom event source.

2.2. Event source in the Administrator perspective

Sourcing events is critical to developing a distributed system that reacts to events.

2.2.1. Creating an event source by using the Administrator perspective

A Knative event source can be any Kubernetes object that generates or imports cloud events, and relays those events to another endpoint, known as a sink.

Prerequisites

  • The OpenShift Serverless Operator and Knative Eventing are installed on your OpenShift Container Platform cluster.
  • You have logged in to the web console and are in the Administrator perspective.
  • You have cluster administrator permissions on OpenShift Container Platform, or you have cluster or dedicated administrator permissions on Red Hat OpenShift Service on AWS or OpenShift Dedicated.

Procedure

  1. In the Administrator perspective of the OpenShift Container Platform web console, navigate to Serverless Eventing.
  2. In the Create list, select Event Source. You will be directed to the Event Sources page.
  3. Select the event source type that you want to create.

2.3. Creating an API server source

The API server source is an event source that can be used to connect an event sink, such as a Knative service, to the Kubernetes API server. The API server source watches for Kubernetes events and forwards them to the Knative Eventing broker.

2.3.1. Creating an API server source by using the web console

After Knative Eventing is installed on your cluster, you can create an API server source by using the web console. Using the OpenShift Container Platform web console provides a streamlined and intuitive user interface to create an event source.

Prerequisites

  • You have logged in to the OpenShift Container Platform web console.
  • The OpenShift Serverless Operator and Knative Eventing are installed on the cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have installed the OpenShift CLI (oc).
Procedure

If you want to re-use an existing service account, you can modify your existing ServiceAccount resource to include the required permissions instead of creating a new resource.

  1. Create a service account, role, and role binding for the event source as a YAML file:

    apiVersion: v1
    kind: ServiceAccount
    metadata:
      name: events-sa
      namespace: default 1
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: Role
    metadata:
      name: event-watcher
      namespace: default 2
    rules:
      - apiGroups:
          - ""
        resources:
          - events
        verbs:
          - get
          - list
          - watch
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: RoleBinding
    metadata:
      name: k8s-ra-event-watcher
      namespace: default 3
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: Role
      name: event-watcher
    subjects:
      - kind: ServiceAccount
        name: events-sa
        namespace: default 4
    1 2 3 4
    Change this namespace to the namespace that you have selected for installing the event source.
  2. Apply the YAML file:

    $ oc apply -f <filename>
  3. In the Developer perspective, navigate to +Add Event Source. The Event Sources page is displayed.
  4. Optional: If you have multiple providers for your event sources, select the required provider from the Providers list to filter the available event sources from the provider.
  5. Select ApiServerSource and then click Create Event Source. The Create Event Source page is displayed.
  6. Configure the ApiServerSource settings by using the Form view or YAML view:

    Note

    You can switch between the Form view and YAML view. The data is persisted when switching between the views.

    1. Enter v1 as the APIVERSION and Event as the KIND.
    2. Select the Service Account Name for the service account that you created.
    3. Select the Sink for the event source. A Sink can be either a Resource, such as a channel, broker, or service, or a URI.
  7. Click Create.

Verification

  • After you have created the API server source, you will see it connected to the service it is sinked to in the Topology view.

    ApiServerSource Topology view
Note

If a URI sink is used, modify the URI by right-clicking on URI sink Edit URI.

Deleting the API server source

  1. Navigate to the Topology view.
  2. Right-click the API server source and select Delete ApiServerSource.

    Delete the ApiServerSource

2.3.2. Creating an API server source by using the Knative CLI

You can use the kn source apiserver create command to create an API server source by using the kn CLI. Using the kn CLI to create an API server source provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator and Knative Eventing are installed on the cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have installed the OpenShift CLI (oc).
  • You have installed the Knative (kn) CLI.
Procedure

If you want to re-use an existing service account, you can modify your existing ServiceAccount resource to include the required permissions instead of creating a new resource.

  1. Create a service account, role, and role binding for the event source as a YAML file:

    apiVersion: v1
    kind: ServiceAccount
    metadata:
      name: events-sa
      namespace: default 1
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: Role
    metadata:
      name: event-watcher
      namespace: default 2
    rules:
      - apiGroups:
          - ""
        resources:
          - events
        verbs:
          - get
          - list
          - watch
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: RoleBinding
    metadata:
      name: k8s-ra-event-watcher
      namespace: default 3
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: Role
      name: event-watcher
    subjects:
      - kind: ServiceAccount
        name: events-sa
        namespace: default 4
    1 2 3 4
    Change this namespace to the namespace that you have selected for installing the event source.
  2. Apply the YAML file:

    $ oc apply -f <filename>
  3. Create an API server source that has an event sink. In the following example, the sink is a broker:

    $ kn source apiserver create <event_source_name> --sink broker:<broker_name> --resource "event:v1" --service-account <service_account_name> --mode Resource
  4. To check that the API server source is set up correctly, create a Knative service that dumps incoming messages to its log:

    $ kn service create <service_name> --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  5. If you used a broker as an event sink, create a trigger to filter events from the default broker to the service:

    $ kn trigger create <trigger_name> --sink ksvc:<service_name>
  6. Create events by launching a pod in the default namespace:

    $ oc create deployment hello-node --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  7. Check that the controller is mapped correctly by inspecting the output generated by the following command:

    $ kn source apiserver describe <source_name>

    Example output

    Name:                mysource
    Namespace:           default
    Annotations:         sources.knative.dev/creator=developer, sources.knative.dev/lastModifier=developer
    Age:                 3m
    ServiceAccountName:  events-sa
    Mode:                Resource
    Sink:
      Name:       default
      Namespace:  default
      Kind:       Broker (eventing.knative.dev/v1)
    Resources:
      Kind:        event (v1)
      Controller:  false
    Conditions:
      OK TYPE                     AGE REASON
      ++ Ready                     3m
      ++ Deployed                  3m
      ++ SinkProvided              3m
      ++ SufficientPermissions     3m
      ++ EventTypesProvided        3m

Verification

You can verify that the Kubernetes events were sent to Knative by looking at the message dumper function logs.

  1. Get the pods:

    $ oc get pods
  2. View the message dumper function logs for the pods:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.apiserver.resource.update
      datacontenttype: application/json
      ...
    Data,
      {
        "apiVersion": "v1",
        "involvedObject": {
          "apiVersion": "v1",
          "fieldPath": "spec.containers{hello-node}",
          "kind": "Pod",
          "name": "hello-node",
          "namespace": "default",
           .....
        },
        "kind": "Event",
        "message": "Started container",
        "metadata": {
          "name": "hello-node.159d7608e3a3572c",
          "namespace": "default",
          ....
        },
        "reason": "Started",
        ...
      }

Deleting the API server source

  1. Delete the trigger:

    $ kn trigger delete <trigger_name>
  2. Delete the event source:

    $ kn source apiserver delete <source_name>
  3. Delete the service account, cluster role, and cluster binding:

    $ oc delete -f authentication.yaml

2.3.2.1. Knative CLI sink flag

When you create an event source by using the Knative (kn) CLI, you can specify a sink where events are sent to from that resource by using the --sink flag. The sink can be any addressable or callable resource that can receive incoming events from other resources.

The following example creates a sink binding that uses a service, http://event-display.svc.cluster.local, as the sink:

Example command using the sink flag

$ kn source binding create bind-heartbeat \
  --namespace sinkbinding-example \
  --subject "Job:batch/v1:app=heartbeat-cron" \
  --sink http://event-display.svc.cluster.local \ 1
  --ce-override "sink=bound"

1
svc in http://event-display.svc.cluster.local determines that the sink is a Knative service. Other default sink prefixes include channel, and broker.

2.3.3. Creating an API server source by using YAML files

Creating Knative resources by using YAML files uses a declarative API, which enables you to describe event sources declaratively and in a reproducible manner. To create an API server source by using YAML, you must create a YAML file that defines an ApiServerSource object, then apply it by using the oc apply command.

Prerequisites

  • The OpenShift Serverless Operator and Knative Eventing are installed on the cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have created the default broker in the same namespace as the one defined in the API server source YAML file.
  • Install the OpenShift CLI (oc).
Procedure

If you want to re-use an existing service account, you can modify your existing ServiceAccount resource to include the required permissions instead of creating a new resource.

  1. Create a service account, role, and role binding for the event source as a YAML file:

    apiVersion: v1
    kind: ServiceAccount
    metadata:
      name: events-sa
      namespace: default 1
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: Role
    metadata:
      name: event-watcher
      namespace: default 2
    rules:
      - apiGroups:
          - ""
        resources:
          - events
        verbs:
          - get
          - list
          - watch
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: RoleBinding
    metadata:
      name: k8s-ra-event-watcher
      namespace: default 3
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: Role
      name: event-watcher
    subjects:
      - kind: ServiceAccount
        name: events-sa
        namespace: default 4
    1 2 3 4
    Change this namespace to the namespace that you have selected for installing the event source.
  2. Apply the YAML file:

    $ oc apply -f <filename>
  3. Create an API server source as a YAML file:

    apiVersion: sources.knative.dev/v1alpha1
    kind: ApiServerSource
    metadata:
      name: testevents
    spec:
      serviceAccountName: events-sa
      mode: Resource
      resources:
        - apiVersion: v1
          kind: Event
      sink:
        ref:
          apiVersion: eventing.knative.dev/v1
          kind: Broker
          name: default
  4. Apply the ApiServerSource YAML file:

    $ oc apply -f <filename>
  5. To check that the API server source is set up correctly, create a Knative service as a YAML file that dumps incoming messages to its log:

    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: event-display
      namespace: default
    spec:
      template:
        spec:
          containers:
            - image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  6. Apply the Service YAML file:

    $ oc apply -f <filename>
  7. Create a Trigger object as a YAML file that filters events from the default broker to the service created in the previous step:

    apiVersion: eventing.knative.dev/v1
    kind: Trigger
    metadata:
      name: event-display-trigger
      namespace: default
    spec:
      broker: default
      subscriber:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: event-display
  8. Apply the Trigger YAML file:

    $ oc apply -f <filename>
  9. Create events by launching a pod in the default namespace:

    $ oc create deployment hello-node --image=quay.io/openshift-knative/knative-eventing-sources-event-display
  10. Check that the controller is mapped correctly, by entering the following command and inspecting the output:

    $ oc get apiserversource.sources.knative.dev testevents -o yaml

    Example output

    apiVersion: sources.knative.dev/v1alpha1
    kind: ApiServerSource
    metadata:
      annotations:
      creationTimestamp: "2020-04-07T17:24:54Z"
      generation: 1
      name: testevents
      namespace: default
      resourceVersion: "62868"
      selfLink: /apis/sources.knative.dev/v1alpha1/namespaces/default/apiserversources/testevents2
      uid: 1603d863-bb06-4d1c-b371-f580b4db99fa
    spec:
      mode: Resource
      resources:
      - apiVersion: v1
        controller: false
        controllerSelector:
          apiVersion: ""
          kind: ""
          name: ""
          uid: ""
        kind: Event
        labelSelector: {}
      serviceAccountName: events-sa
      sink:
        ref:
          apiVersion: eventing.knative.dev/v1
          kind: Broker
          name: default

Verification

To verify that the Kubernetes events were sent to Knative, you can look at the message dumper function logs.

  1. Get the pods by entering the following command:

    $ oc get pods
  2. View the message dumper function logs for the pods by entering the following command:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.apiserver.resource.update
      datacontenttype: application/json
      ...
    Data,
      {
        "apiVersion": "v1",
        "involvedObject": {
          "apiVersion": "v1",
          "fieldPath": "spec.containers{hello-node}",
          "kind": "Pod",
          "name": "hello-node",
          "namespace": "default",
           .....
        },
        "kind": "Event",
        "message": "Started container",
        "metadata": {
          "name": "hello-node.159d7608e3a3572c",
          "namespace": "default",
          ....
        },
        "reason": "Started",
        ...
      }

Deleting the API server source

  1. Delete the trigger:

    $ oc delete -f trigger.yaml
  2. Delete the event source:

    $ oc delete -f k8s-events.yaml
  3. Delete the service account, cluster role, and cluster binding:

    $ oc delete -f authentication.yaml

2.4. Creating a ping source

A ping source is an event source that can be used to periodically send ping events with a constant payload to an event consumer. A ping source can be used to schedule sending events, similar to a timer.

2.4.1. Creating a ping source by using the web console

After Knative Eventing is installed on your cluster, you can create a ping source by using the web console. Using the OpenShift Container Platform web console provides a streamlined and intuitive user interface to create an event source.

Prerequisites

  • You have logged in to the OpenShift Container Platform web console.
  • The OpenShift Serverless Operator, Knative Serving and Knative Eventing are installed on the cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  1. To verify that the ping source is working, create a simple Knative service that dumps incoming messages to the logs of the service.

    1. In the Developer perspective, navigate to +Add YAML.
    2. Copy the example YAML:

      apiVersion: serving.knative.dev/v1
      kind: Service
      metadata:
        name: event-display
      spec:
        template:
          spec:
            containers:
              - image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest
    3. Click Create.
  2. Create a ping source in the same namespace as the service created in the previous step, or any other sink that you want to send events to.

    1. In the Developer perspective, navigate to +Add Event Source. The Event Sources page is displayed.
    2. Optional: If you have multiple providers for your event sources, select the required provider from the Providers list to filter the available event sources from the provider.
    3. Select Ping Source and then click Create Event Source. The Create Event Source page is displayed.

      Note

      You can configure the PingSource settings by using the Form view or YAML view and can switch between the views. The data is persisted when switching between the views.

    4. Enter a value for Schedule. In this example, the value is */2 * * * *, which creates a PingSource that sends a message every two minutes.
    5. Optional: You can enter a value for Data, which is the message payload.
    6. Select a Sink. This can be either a Resource or a URI. In this example, the event-display service created in the previous step is used as the Resource sink.
    7. Click Create.

Verification

You can verify that the ping source was created and is connected to the sink by viewing the Topology page.

  1. In the Developer perspective, navigate to Topology.
  2. View the ping source and sink.

    View the ping source and service in the Topology view

Deleting the ping source

  1. Navigate to the Topology view.
  2. Right-click the API server source and select Delete Ping Source.

2.4.2. Creating a ping source by using the Knative CLI

You can use the kn source ping create command to create a ping source by using the Knative (kn) CLI. Using the Knative CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving and Knative Eventing are installed on the cluster.
  • You have installed the Knative (kn) CLI.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • Optional: If you want to use the verification steps for this procedure, install the OpenShift CLI (oc).

Procedure

  1. To verify that the ping source is working, create a simple Knative service that dumps incoming messages to the service logs:

    $ kn service create event-display \
        --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  2. For each set of ping events that you want to request, create a ping source in the same namespace as the event consumer:

    $ kn source ping create test-ping-source \
        --schedule "*/2 * * * *" \
        --data '{"message": "Hello world!"}' \
        --sink ksvc:event-display
  3. Check that the controller is mapped correctly by entering the following command and inspecting the output:

    $ kn source ping describe test-ping-source

    Example output

    Name:         test-ping-source
    Namespace:    default
    Annotations:  sources.knative.dev/creator=developer, sources.knative.dev/lastModifier=developer
    Age:          15s
    Schedule:     */2 * * * *
    Data:         {"message": "Hello world!"}
    
    Sink:
      Name:       event-display
      Namespace:  default
      Resource:   Service (serving.knative.dev/v1)
    
    Conditions:
      OK TYPE                 AGE REASON
      ++ Ready                 8s
      ++ Deployed              8s
      ++ SinkProvided         15s
      ++ ValidSchedule        15s
      ++ EventTypeProvided    15s
      ++ ResourcesCorrect     15s

Verification

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the logs of the sink pod.

By default, Knative services terminate their pods if no traffic is received within a 60 second period. The example shown in this guide creates a ping source that sends a message every 2 minutes, so each message should be observed in a newly created pod.

  1. Watch for new pods created:

    $ watch oc get pods
  2. Cancel watching the pods using Ctrl+C, then look at the logs of the created pod:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.sources.ping
      source: /apis/v1/namespaces/default/pingsources/test-ping-source
      id: 99e4f4f6-08ff-4bff-acf1-47f61ded68c9
      time: 2020-04-07T16:16:00.000601161Z
      datacontenttype: application/json
    Data,
      {
        "message": "Hello world!"
      }

Deleting the ping source

  • Delete the ping source:

    $ kn delete pingsources.sources.knative.dev <ping_source_name>

2.4.2.1. Knative CLI sink flag

When you create an event source by using the Knative (kn) CLI, you can specify a sink where events are sent to from that resource by using the --sink flag. The sink can be any addressable or callable resource that can receive incoming events from other resources.

The following example creates a sink binding that uses a service, http://event-display.svc.cluster.local, as the sink:

Example command using the sink flag

$ kn source binding create bind-heartbeat \
  --namespace sinkbinding-example \
  --subject "Job:batch/v1:app=heartbeat-cron" \
  --sink http://event-display.svc.cluster.local \ 1
  --ce-override "sink=bound"

1
svc in http://event-display.svc.cluster.local determines that the sink is a Knative service. Other default sink prefixes include channel, and broker.

2.4.3. Creating a ping source by using YAML

Creating Knative resources by using YAML files uses a declarative API, which enables you to describe event sources declaratively and in a reproducible manner. To create a serverless ping source by using YAML, you must create a YAML file that defines a PingSource object, then apply it by using oc apply.

Example PingSource object

apiVersion: sources.knative.dev/v1
kind: PingSource
metadata:
  name: test-ping-source
spec:
  schedule: "*/2 * * * *" 1
  data: '{"message": "Hello world!"}' 2
  sink: 3
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: event-display

1
The schedule of the event specified using CRON expression.
2
The event message body expressed as a JSON encoded data string.
3
These are the details of the event consumer. In this example, we are using a Knative service named event-display.

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving and Knative Eventing are installed on the cluster.
  • Install the OpenShift CLI (oc).
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  1. To verify that the ping source is working, create a simple Knative service that dumps incoming messages to the service’s logs.

    1. Create a service YAML file:

      apiVersion: serving.knative.dev/v1
      kind: Service
      metadata:
        name: event-display
      spec:
        template:
          spec:
            containers:
              - image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest
    2. Create the service:

      $ oc apply -f <filename>
  2. For each set of ping events that you want to request, create a ping source in the same namespace as the event consumer.

    1. Create a YAML file for the ping source:

      apiVersion: sources.knative.dev/v1
      kind: PingSource
      metadata:
        name: test-ping-source
      spec:
        schedule: "*/2 * * * *"
        data: '{"message": "Hello world!"}'
        sink:
          ref:
            apiVersion: serving.knative.dev/v1
            kind: Service
            name: event-display
    2. Create the ping source:

      $ oc apply -f <filename>
  3. Check that the controller is mapped correctly by entering the following command:

    $ oc get pingsource.sources.knative.dev <ping_source_name> -oyaml

    Example output

    apiVersion: sources.knative.dev/v1
    kind: PingSource
    metadata:
      annotations:
        sources.knative.dev/creator: developer
        sources.knative.dev/lastModifier: developer
      creationTimestamp: "2020-04-07T16:11:14Z"
      generation: 1
      name: test-ping-source
      namespace: default
      resourceVersion: "55257"
      selfLink: /apis/sources.knative.dev/v1/namespaces/default/pingsources/test-ping-source
      uid: 3d80d50b-f8c7-4c1b-99f7-3ec00e0a8164
    spec:
      data: '{ value: "hello" }'
      schedule: '*/2 * * * *'
      sink:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: event-display
          namespace: default

Verification

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the sink pod’s logs.

By default, Knative services terminate their pods if no traffic is received within a 60 second period. The example shown in this guide creates a PingSource that sends a message every 2 minutes, so each message should be observed in a newly created pod.

  1. Watch for new pods created:

    $ watch oc get pods
  2. Cancel watching the pods using Ctrl+C, then look at the logs of the created pod:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.sources.ping
      source: /apis/v1/namespaces/default/pingsources/test-ping-source
      id: 042ff529-240e-45ee-b40c-3a908129853e
      time: 2020-04-07T16:22:00.000791674Z
      datacontenttype: application/json
    Data,
      {
        "message": "Hello world!"
      }

Deleting the ping source

  • Delete the ping source:

    $ oc delete -f <filename>

    Example command

    $ oc delete -f ping-source.yaml

2.5. Source for Apache Kafka

You can create an Apache Kafka source that reads events from an Apache Kafka cluster and passes these events to a sink. You can create a Kafka source by using the OpenShift Container Platform web console, the Knative (kn) CLI, or by creating a KafkaSource object directly as a YAML file and using the OpenShift CLI (oc) to apply it.

Note

See the documentation for Installing Knative broker for Apache Kafka.

2.5.1. Creating an Apache Kafka event source by using the web console

After the Knative broker implementation for Apache Kafka is installed on your cluster, you can create an Apache Kafka source by using the web console. Using the OpenShift Container Platform web console provides a streamlined and intuitive user interface to create a Kafka source.

Prerequisites

  • The OpenShift Serverless Operator, Knative Eventing, and the KnativeKafka custom resource are installed on your cluster.
  • You have logged in to the web console.
  • You have access to a Red Hat AMQ Streams (Kafka) cluster that produces the Kafka messages you want to import.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  1. In the Developer perspective, navigate to the +Add page and select Event Source.
  2. In the Event Sources page, select Kafka Source in the Type section.
  3. Configure the Kafka Source settings:

    1. Add a comma-separated list of Bootstrap Servers.
    2. Add a comma-separated list of Topics.
    3. Add a Consumer Group.
    4. Select the Service Account Name for the service account that you created.
    5. Select the Sink for the event source. A Sink can be either a Resource, such as a channel, broker, or service, or a URI.
    6. Enter a Name for the Kafka event source.
  4. Click Create.

Verification

You can verify that the Kafka event source was created and is connected to the sink by viewing the Topology page.

  1. In the Developer perspective, navigate to Topology.
  2. View the Kafka event source and sink.

    View the Kafka source and service in the Topology view

2.5.2. Creating an Apache Kafka event source by using the Knative CLI

You can use the kn source kafka create command to create a Kafka source by using the Knative (kn) CLI. Using the Knative CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator, Knative Eventing, Knative Serving, and the KnativeKafka custom resource (CR) are installed on your cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have access to a Red Hat AMQ Streams (Kafka) cluster that produces the Kafka messages you want to import.
  • You have installed the Knative (kn) CLI.
  • Optional: You have installed the OpenShift CLI (oc) if you want to use the verification steps in this procedure.

Procedure

  1. To verify that the Kafka event source is working, create a Knative service that dumps incoming events into the service logs:

    $ kn service create event-display \
        --image quay.io/openshift-knative/knative-eventing-sources-event-display
  2. Create a KafkaSource CR:

    $ kn source kafka create <kafka_source_name> \
        --servers <cluster_kafka_bootstrap>.kafka.svc:9092 \
        --topics <topic_name> --consumergroup my-consumer-group \
        --sink event-display
    Note

    Replace the placeholder values in this command with values for your source name, bootstrap servers, and topics.

    The --servers, --topics, and --consumergroup options specify the connection parameters to the Kafka cluster. The --consumergroup option is optional.

  3. Optional: View details about the KafkaSource CR you created:

    $ kn source kafka describe <kafka_source_name>

    Example output

    Name:              example-kafka-source
    Namespace:         kafka
    Age:               1h
    BootstrapServers:  example-cluster-kafka-bootstrap.kafka.svc:9092
    Topics:            example-topic
    ConsumerGroup:     example-consumer-group
    
    Sink:
      Name:       event-display
      Namespace:  default
      Resource:   Service (serving.knative.dev/v1)
    
    Conditions:
      OK TYPE            AGE REASON
      ++ Ready            1h
      ++ Deployed         1h
      ++ SinkProvided     1h

Verification steps

  1. Trigger the Kafka instance to send a message to the topic:

    $ oc -n kafka run kafka-producer \
        -ti --image=quay.io/strimzi/kafka:latest-kafka-2.7.0 --rm=true \
        --restart=Never -- bin/kafka-console-producer.sh \
        --broker-list <cluster_kafka_bootstrap>:9092 --topic my-topic

    Enter the message in the prompt. This command assumes that:

    • The Kafka cluster is installed in the kafka namespace.
    • The KafkaSource object has been configured to use the my-topic topic.
  2. Verify that the message arrived by viewing the logs:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.kafka.event
      source: /apis/v1/namespaces/default/kafkasources/example-kafka-source#example-topic
      subject: partition:46#0
      id: partition:46/offset:0
      time: 2021-03-10T11:21:49.4Z
    Extensions,
      traceparent: 00-161ff3815727d8755848ec01c866d1cd-7ff3916c44334678-00
    Data,
      Hello!

2.5.2.1. Knative CLI sink flag

When you create an event source by using the Knative (kn) CLI, you can specify a sink where events are sent to from that resource by using the --sink flag. The sink can be any addressable or callable resource that can receive incoming events from other resources.

The following example creates a sink binding that uses a service, http://event-display.svc.cluster.local, as the sink:

Example command using the sink flag

$ kn source binding create bind-heartbeat \
  --namespace sinkbinding-example \
  --subject "Job:batch/v1:app=heartbeat-cron" \
  --sink http://event-display.svc.cluster.local \ 1
  --ce-override "sink=bound"

1
svc in http://event-display.svc.cluster.local determines that the sink is a Knative service. Other default sink prefixes include channel, and broker.

2.5.3. Creating an Apache Kafka event source by using YAML

Creating Knative resources by using YAML files uses a declarative API, which enables you to describe applications declaratively and in a reproducible manner. To create a Kafka source by using YAML, you must create a YAML file that defines a KafkaSource object, then apply it by using the oc apply command.

Prerequisites

  • The OpenShift Serverless Operator, Knative Eventing, and the KnativeKafka custom resource are installed on your cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have access to a Red Hat AMQ Streams (Kafka) cluster that produces the Kafka messages you want to import.
  • Install the OpenShift CLI (oc).

Procedure

  1. Create a KafkaSource object as a YAML file:

    apiVersion: sources.knative.dev/v1beta1
    kind: KafkaSource
    metadata:
      name: <source_name>
    spec:
      consumerGroup: <group_name> 1
      bootstrapServers:
      - <list_of_bootstrap_servers>
      topics:
      - <list_of_topics> 2
      sink:
      - <list_of_sinks> 3
    1
    A consumer group is a group of consumers that use the same group ID, and consume data from a topic.
    2
    A topic provides a destination for the storage of data. Each topic is split into one or more partitions.
    3
    A sink specifies where events are sent to from a source.
    Important

    Only the v1beta1 version of the API for KafkaSource objects on OpenShift Serverless is supported. Do not use the v1alpha1 version of this API, as this version is now deprecated.

    Example KafkaSource object

    apiVersion: sources.knative.dev/v1beta1
    kind: KafkaSource
    metadata:
      name: kafka-source
    spec:
      consumerGroup: knative-group
      bootstrapServers:
      - my-cluster-kafka-bootstrap.kafka:9092
      topics:
      - knative-demo-topic
      sink:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: event-display

  2. Apply the KafkaSource YAML file:

    $ oc apply -f <filename>

Verification

  • Verify that the Kafka event source was created by entering the following command:

    $ oc get pods

    Example output

    NAME                                    READY     STATUS    RESTARTS   AGE
    kafkasource-kafka-source-5ca0248f-...   1/1       Running   0          13m

2.5.4. Configuring SASL authentication for Apache Kafka sources

Simple Authentication and Security Layer (SASL) is used by Apache Kafka for authentication. If you use SASL authentication on your cluster, users must provide credentials to Knative for communicating with the Kafka cluster; otherwise events cannot be produced or consumed.

Prerequisites

  • You have cluster or dedicated administrator permissions on OpenShift Container Platform.
  • The OpenShift Serverless Operator, Knative Eventing, and the KnativeKafka CR are installed on your OpenShift Container Platform cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have a username and password for a Kafka cluster.
  • You have chosen the SASL mechanism to use, for example, PLAIN, SCRAM-SHA-256, or SCRAM-SHA-512.
  • If TLS is enabled, you also need the ca.crt certificate file for the Kafka cluster.
  • You have installed the OpenShift (oc) CLI.

Procedure

  1. Create the certificate files as secrets in your chosen namespace:

    $ oc create secret -n <namespace> generic <kafka_auth_secret> \
      --from-file=ca.crt=caroot.pem \
      --from-literal=password="SecretPassword" \
      --from-literal=saslType="SCRAM-SHA-512" \ 1
      --from-literal=user="my-sasl-user"
    1
    The SASL type can be PLAIN, SCRAM-SHA-256, or SCRAM-SHA-512.
  2. Create or modify your Kafka source so that it contains the following spec configuration:

    apiVersion: sources.knative.dev/v1beta1
    kind: KafkaSource
    metadata:
      name: example-source
    spec:
    ...
      net:
        sasl:
          enable: true
          user:
            secretKeyRef:
              name: <kafka_auth_secret>
              key: user
          password:
            secretKeyRef:
              name: <kafka_auth_secret>
              key: password
          type:
            secretKeyRef:
              name: <kafka_auth_secret>
              key: saslType
        tls:
          enable: true
          caCert: 1
            secretKeyRef:
              name: <kafka_auth_secret>
              key: ca.crt
    ...
    1
    The caCert spec is not required if you are using a public cloud Kafka service.

2.6. Custom event sources

If you need to ingress events from an event producer that is not included in Knative, or from a producer that emits events which are not in the CloudEvent format, you can do this by creating a custom event source. You can create a custom event source by using one of the following methods:

  • Use a PodSpecable object as an event source, by creating a sink binding.
  • Use a container as an event source, by creating a container source.

2.6.1. Sink binding

The SinkBinding object supports decoupling event production from delivery addressing. Sink binding is used to connect event producers to an event consumer, or sink. An event producer is a Kubernetes resource that embeds a PodSpec template and produces events. A sink is an addressable Kubernetes object that can receive events.

The SinkBinding object injects environment variables into the PodTemplateSpec of the sink, which means that the application code does not need to interact directly with the Kubernetes API to locate the event destination. These environment variables are as follows:

K_SINK
The URL of the resolved sink.
K_CE_OVERRIDES
A JSON object that specifies overrides to the outbound event.
Note

The SinkBinding object currently does not support custom revision names for services.

2.6.1.1. Creating a sink binding by using YAML

Creating Knative resources by using YAML files uses a declarative API, which enables you to describe event sources declaratively and in a reproducible manner. To create a sink binding by using YAML, you must create a YAML file that defines an SinkBinding object, then apply it by using the oc apply command.

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving and Knative Eventing are installed on the cluster.
  • Install the OpenShift CLI (oc).
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  1. To check that sink binding is set up correctly, create a Knative event display service, or event sink, that dumps incoming messages to its log.

    1. Create a service YAML file:

      Example service YAML file

      apiVersion: serving.knative.dev/v1
      kind: Service
      metadata:
        name: event-display
      spec:
        template:
          spec:
            containers:
              - image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest

    2. Create the service:

      $ oc apply -f <filename>
  2. Create a sink binding instance that directs events to the service.

    1. Create a sink binding YAML file:

      Example service YAML file

      apiVersion: sources.knative.dev/v1alpha1
      kind: SinkBinding
      metadata:
        name: bind-heartbeat
      spec:
        subject:
          apiVersion: batch/v1
          kind: Job 1
          selector:
            matchLabels:
              app: heartbeat-cron
      
        sink:
          ref:
            apiVersion: serving.knative.dev/v1
            kind: Service
            name: event-display

      1
      In this example, any Job with the label app: heartbeat-cron will be bound to the event sink.
    2. Create the sink binding:

      $ oc apply -f <filename>
  3. Create a CronJob object.

    1. Create a cron job YAML file:

      Example cron job YAML file

      apiVersion: batch/v1
      kind: CronJob
      metadata:
        name: heartbeat-cron
      spec:
        # Run every minute
        schedule: "* * * * *"
        jobTemplate:
          metadata:
            labels:
              app: heartbeat-cron
              bindings.knative.dev/include: "true"
          spec:
            template:
              spec:
                restartPolicy: Never
                containers:
                  - name: single-heartbeat
                    image: quay.io/openshift-knative/heartbeats:latest
                    args:
                      - --period=1
                    env:
                      - name: ONE_SHOT
                        value: "true"
                      - name: POD_NAME
                        valueFrom:
                          fieldRef:
                            fieldPath: metadata.name
                      - name: POD_NAMESPACE
                        valueFrom:
                          fieldRef:
                            fieldPath: metadata.namespace

      Important

      To use sink binding, you must manually add a bindings.knative.dev/include=true label to your Knative resources.

      For example, to add this label to a CronJob resource, add the following lines to the Job resource YAML definition:

        jobTemplate:
          metadata:
            labels:
              app: heartbeat-cron
              bindings.knative.dev/include: "true"
    2. Create the cron job:

      $ oc apply -f <filename>
  4. Check that the controller is mapped correctly by entering the following command and inspecting the output:

    $ oc get sinkbindings.sources.knative.dev bind-heartbeat -oyaml

    Example output

    spec:
      sink:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: event-display
          namespace: default
      subject:
        apiVersion: batch/v1
        kind: Job
        namespace: default
        selector:
          matchLabels:
            app: heartbeat-cron

Verification

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the message dumper function logs.

  1. Enter the command:

    $ oc get pods
  2. Enter the command:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.eventing.samples.heartbeat
      source: https://knative.dev/eventing-contrib/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": 1,
        "label": ""
      }

2.6.1.2. Creating a sink binding by using the Knative CLI

You can use the kn source binding create command to create a sink binding by using the Knative (kn) CLI. Using the Knative CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving and Knative Eventing are installed on the cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • Install the Knative (kn) CLI.
  • Install the OpenShift CLI (oc).
Note

The following procedure requires you to create YAML files.

If you change the names of the YAML files from those used in the examples, you must ensure that you also update the corresponding CLI commands.

Procedure

  1. To check that sink binding is set up correctly, create a Knative event display service, or event sink, that dumps incoming messages to its log:

    $ kn service create event-display --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  2. Create a sink binding instance that directs events to the service:

    $ kn source binding create bind-heartbeat --subject Job:batch/v1:app=heartbeat-cron --sink ksvc:event-display
  3. Create a CronJob object.

    1. Create a cron job YAML file:

      Example cron job YAML file

      apiVersion: batch/v1
      kind: CronJob
      metadata:
        name: heartbeat-cron
      spec:
        # Run every minute
        schedule: "* * * * *"
        jobTemplate:
          metadata:
            labels:
              app: heartbeat-cron
              bindings.knative.dev/include: "true"
          spec:
            template:
              spec:
                restartPolicy: Never
                containers:
                  - name: single-heartbeat
                    image: quay.io/openshift-knative/heartbeats:latest
                    args:
                      - --period=1
                    env:
                      - name: ONE_SHOT
                        value: "true"
                      - name: POD_NAME
                        valueFrom:
                          fieldRef:
                            fieldPath: metadata.name
                      - name: POD_NAMESPACE
                        valueFrom:
                          fieldRef:
                            fieldPath: metadata.namespace

      Important

      To use sink binding, you must manually add a bindings.knative.dev/include=true label to your Knative CRs.

      For example, to add this label to a CronJob CR, add the following lines to the Job CR YAML definition:

        jobTemplate:
          metadata:
            labels:
              app: heartbeat-cron
              bindings.knative.dev/include: "true"
    2. Create the cron job:

      $ oc apply -f <filename>
  4. Check that the controller is mapped correctly by entering the following command and inspecting the output:

    $ kn source binding describe bind-heartbeat

    Example output

    Name:         bind-heartbeat
    Namespace:    demo-2
    Annotations:  sources.knative.dev/creator=minikube-user, sources.knative.dev/lastModifier=minikub ...
    Age:          2m
    Subject:
      Resource:   job (batch/v1)
      Selector:
        app:      heartbeat-cron
    Sink:
      Name:       event-display
      Resource:   Service (serving.knative.dev/v1)
    
    Conditions:
      OK TYPE     AGE REASON
      ++ Ready     2m

Verification

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the message dumper function logs.

  • View the message dumper function logs by entering the following commands:

    $ oc get pods
    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.eventing.samples.heartbeat
      source: https://knative.dev/eventing-contrib/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": 1,
        "label": ""
      }

2.6.1.2.1. Knative CLI sink flag

When you create an event source by using the Knative (kn) CLI, you can specify a sink where events are sent to from that resource by using the --sink flag. The sink can be any addressable or callable resource that can receive incoming events from other resources.

The following example creates a sink binding that uses a service, http://event-display.svc.cluster.local, as the sink:

Example command using the sink flag

$ kn source binding create bind-heartbeat \
  --namespace sinkbinding-example \
  --subject "Job:batch/v1:app=heartbeat-cron" \
  --sink http://event-display.svc.cluster.local \ 1
  --ce-override "sink=bound"

1
svc in http://event-display.svc.cluster.local determines that the sink is a Knative service. Other default sink prefixes include channel, and broker.

2.6.1.3. Creating a sink binding by using the web console

After Knative Eventing is installed on your cluster, you can create a sink binding by using the web console. Using the OpenShift Container Platform web console provides a streamlined and intuitive user interface to create an event source.

Prerequisites

  • You have logged in to the OpenShift Container Platform web console.
  • The OpenShift Serverless Operator, Knative Serving, and Knative Eventing are installed on your OpenShift Container Platform cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  1. Create a Knative service to use as a sink:

    1. In the Developer perspective, navigate to +Add YAML.
    2. Copy the example YAML:

      apiVersion: serving.knative.dev/v1
      kind: Service
      metadata:
        name: event-display
      spec:
        template:
          spec:
            containers:
              - image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest
    3. Click Create.
  2. Create a CronJob resource that is used as an event source and sends an event every minute.

    1. In the Developer perspective, navigate to +Add YAML.
    2. Copy the example YAML:

      apiVersion: batch/v1
      kind: CronJob
      metadata:
        name: heartbeat-cron
      spec:
        # Run every minute
        schedule: "*/1 * * * *"
        jobTemplate:
          metadata:
            labels:
              app: heartbeat-cron
              bindings.knative.dev/include: true 1
          spec:
            template:
              spec:
                restartPolicy: Never
                containers:
                  - name: single-heartbeat
                    image: quay.io/openshift-knative/heartbeats
                    args:
                    - --period=1
                    env:
                      - name: ONE_SHOT
                        value: "true"
                      - name: POD_NAME
                        valueFrom:
                          fieldRef:
                            fieldPath: metadata.name
                      - name: POD_NAMESPACE
                        valueFrom:
                          fieldRef:
                            fieldPath: metadata.namespace
      1
      Ensure that you include the bindings.knative.dev/include: true label. The default namespace selection behavior of OpenShift Serverless uses inclusion mode.
    3. Click Create.
  3. Create a sink binding in the same namespace as the service created in the previous step, or any other sink that you want to send events to.

    1. In the Developer perspective, navigate to +Add Event Source. The Event Sources page is displayed.
    2. Optional: If you have multiple providers for your event sources, select the required provider from the Providers list to filter the available event sources from the provider.
    3. Select Sink Binding and then click Create Event Source. The Create Event Source page is displayed.

      Note

      You can configure the Sink Binding settings by using the Form view or YAML view and can switch between the views. The data is persisted when switching between the views.

    4. In the apiVersion field enter batch/v1.
    5. In the Kind field enter Job.

      Note

      The CronJob kind is not supported directly by OpenShift Serverless sink binding, so the Kind field must target the Job objects created by the cron job, rather than the cron job object itself.

    6. Select a Sink. This can be either a Resource or a URI. In this example, the event-display service created in the previous step is used as the Resource sink.
    7. In the Match labels section:

      1. Enter app in the Name field.
      2. Enter heartbeat-cron in the Value field.

        Note

        The label selector is required when using cron jobs with sink binding, rather than the resource name. This is because jobs created by a cron job do not have a predictable name, and contain a randomly generated string in their name. For example, hearthbeat-cron-1cc23f.

    8. Click Create.

Verification

You can verify that the sink binding, sink, and cron job have been created and are working correctly by viewing the Topology page and pod logs.

  1. In the Developer perspective, navigate to Topology.
  2. View the sink binding, sink, and heartbeats cron job.

    View the sink binding and service in the Topology view
  3. Observe that successful jobs are being registered by the cron job once the sink binding is added. This means that the sink binding is successfully reconfiguring the jobs created by the cron job.
  4. Browse the logs of the event-display service pod to see events produced by the heartbeats cron job.

2.6.1.4. Sink binding reference

You can use a PodSpecable object as an event source by creating a sink binding. You can configure multiple parameters when creating a SinkBinding object.

SinkBinding objects support the following parameters:

FieldDescriptionRequired or optional

apiVersion

Specifies the API version, for example sources.knative.dev/v1.

Required

kind

Identifies this resource object as a SinkBinding object.

Required

metadata

Specifies metadata that uniquely identifies the SinkBinding object. For example, a name.

Required

spec

Specifies the configuration information for this SinkBinding object.

Required

spec.sink

A reference to an object that resolves to a URI to use as the sink.

Required

spec.subject

References the resources for which the runtime contract is augmented by binding implementations.

Required

spec.ceOverrides

Defines overrides to control the output format and modifications to the event sent to the sink.

Optional

2.6.1.4.1. Subject parameter

The Subject parameter references the resources for which the runtime contract is augmented by binding implementations. You can configure multiple fields for a Subject definition.

The Subject definition supports the following fields:

FieldDescriptionRequired or optional

apiVersion

API version of the referent.

Required

kind

Kind of the referent.

Required

namespace

Namespace of the referent. If omitted, this defaults to the namespace of the object.

Optional

name

Name of the referent.

Do not use if you configure selector.

selector

Selector of the referents.

Do not use if you configure name.

selector.matchExpressions

A list of label selector requirements.

Only use one of either matchExpressions or matchLabels.

selector.matchExpressions.key

The label key that the selector applies to.

Required if using matchExpressions.

selector.matchExpressions.operator

Represents a key’s relationship to a set of values. Valid operators are In, NotIn, Exists and DoesNotExist.

Required if using matchExpressions.

selector.matchExpressions.values

An array of string values. If the operator parameter value is In or NotIn, the values array must be non-empty. If the operator parameter value is Exists or DoesNotExist, the values array must be empty. This array is replaced during a strategic merge patch.

Required if using matchExpressions.

selector.matchLabels

A map of key-value pairs. Each key-value pair in the matchLabels map is equivalent to an element of matchExpressions, where the key field is matchLabels.<key>, the operator is In, and the values array contains only matchLabels.<value>.

Only use one of either matchExpressions or matchLabels.

Subject parameter examples

Given the following YAML, the Deployment object named mysubject in the default namespace is selected:

apiVersion: sources.knative.dev/v1
kind: SinkBinding
metadata:
  name: bind-heartbeat
spec:
  subject:
    apiVersion: apps/v1
    kind: Deployment
    namespace: default
    name: mysubject
  ...

Given the following YAML, any Job object with the label working=example in the default namespace is selected:

apiVersion: sources.knative.dev/v1
kind: SinkBinding
metadata:
  name: bind-heartbeat
spec:
  subject:
    apiVersion: batch/v1
    kind: Job
    namespace: default
    selector:
      matchLabels:
        working: example
  ...

Given the following YAML, any Pod object with the label working=example or working=sample in the default namespace is selected:

apiVersion: sources.knative.dev/v1
kind: SinkBinding
metadata:
  name: bind-heartbeat
spec:
  subject:
    apiVersion: v1
    kind: Pod
    namespace: default
    selector:
      - matchExpression:
        key: working
        operator: In
        values:
          - example
          - sample
  ...
2.6.1.4.2. CloudEvent overrides

A ceOverrides definition provides overrides that control the CloudEvent’s output format and modifications sent to the sink. You can configure multiple fields for the ceOverrides definition.

A ceOverrides definition supports the following fields:

FieldDescriptionRequired or optional

extensions

Specifies which attributes are added or overridden on the outbound event. Each extensions key-value pair is set independently on the event as an attribute extension.

Optional

Note

Only valid CloudEvent attribute names are allowed as extensions. You cannot set the spec defined attributes from the extensions override configuration. For example, you can not modify the type attribute.

CloudEvent Overrides example

apiVersion: sources.knative.dev/v1
kind: SinkBinding
metadata:
  name: bind-heartbeat
spec:
  ...
  ceOverrides:
    extensions:
      extra: this is an extra attribute
      additional: 42

This sets the K_CE_OVERRIDES environment variable on the subject:

Example output

{ "extensions": { "extra": "this is an extra attribute", "additional": "42" } }

2.6.1.4.3. The include label

To use a sink binding, you need to do assign the bindings.knative.dev/include: "true" label to either the resource or the namespace that the resource is included in. If the resource definition does not include the label, a cluster administrator can attach it to the namespace by running:

$ oc label namespace <namespace> bindings.knative.dev/include=true

2.6.2. Container source

Container sources create a container image that generates events and sends events to a sink. You can use a container source to create a custom event source, by creating a container image and a ContainerSource object that uses your image URI.

2.6.2.1. Guidelines for creating a container image

Two environment variables are injected by the container source controller: K_SINK and K_CE_OVERRIDES. These variables are resolved from the sink and ceOverrides spec, respectively. Events are sent to the sink URI specified in the K_SINK environment variable. The message must be sent as a POST using the CloudEvent HTTP format.

Example container images

The following is an example of a heartbeats container image:

package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"
	"strconv"
	"time"

	duckv1 "knative.dev/pkg/apis/duck/v1"

	cloudevents "github.com/cloudevents/sdk-go/v2"
	"github.com/kelseyhightower/envconfig"
)

type Heartbeat struct {
	Sequence int    `json:"id"`
	Label    string `json:"label"`
}

var (
	eventSource string
	eventType   string
	sink        string
	label       string
	periodStr   string
)

func init() {
	flag.StringVar(&eventSource, "eventSource", "", "the event-source (CloudEvents)")
	flag.StringVar(&eventType, "eventType", "dev.knative.eventing.samples.heartbeat", "the event-type (CloudEvents)")
	flag.StringVar(&sink, "sink", "", "the host url to heartbeat to")
	flag.StringVar(&label, "label", "", "a special label")
	flag.StringVar(&periodStr, "period", "5", "the number of seconds between heartbeats")
}

type envConfig struct {
	// Sink URL where to send heartbeat cloud events
	Sink string `envconfig:"K_SINK"`

	// CEOverrides are the CloudEvents overrides to be applied to the outbound event.
	CEOverrides string `envconfig:"K_CE_OVERRIDES"`

	// Name of this pod.
	Name string `envconfig:"POD_NAME" required:"true"`

	// Namespace this pod exists in.
	Namespace string `envconfig:"POD_NAMESPACE" required:"true"`

	// Whether to run continuously or exit.
	OneShot bool `envconfig:"ONE_SHOT" default:"false"`
}

func main() {
	flag.Parse()

	var env envConfig
	if err := envconfig.Process("", &env); err != nil {
		log.Printf("[ERROR] Failed to process env var: %s", err)
		os.Exit(1)
	}

	if env.Sink != "" {
		sink = env.Sink
	}

	var ceOverrides *duckv1.CloudEventOverrides
	if len(env.CEOverrides) > 0 {
		overrides := duckv1.CloudEventOverrides{}
		err := json.Unmarshal([]byte(env.CEOverrides), &overrides)
		if err != nil {
			log.Printf("[ERROR] Unparseable CloudEvents overrides %s: %v", env.CEOverrides, err)
			os.Exit(1)
		}
		ceOverrides = &overrides
	}

	p, err := cloudevents.NewHTTP(cloudevents.WithTarget(sink))
	if err != nil {
		log.Fatalf("failed to create http protocol: %s", err.Error())
	}

	c, err := cloudevents.NewClient(p, cloudevents.WithUUIDs(), cloudevents.WithTimeNow())
	if err != nil {
		log.Fatalf("failed to create client: %s", err.Error())
	}

	var period time.Duration
	if p, err := strconv.Atoi(periodStr); err != nil {
		period = time.Duration(5) * time.Second
	} else {
		period = time.Duration(p) * time.Second
	}

	if eventSource == "" {
		eventSource = fmt.Sprintf("https://knative.dev/eventing-contrib/cmd/heartbeats/#%s/%s", env.Namespace, env.Name)
		log.Printf("Heartbeats Source: %s", eventSource)
	}

	if len(label) > 0 && label[0] == '"' {
		label, _ = strconv.Unquote(label)
	}
	hb := &Heartbeat{
		Sequence: 0,
		Label:    label,
	}
	ticker := time.NewTicker(period)
	for {
		hb.Sequence++

		event := cloudevents.NewEvent("1.0")
		event.SetType(eventType)
		event.SetSource(eventSource)
		event.SetExtension("the", 42)
		event.SetExtension("heart", "yes")
		event.SetExtension("beats", true)

		if ceOverrides != nil && ceOverrides.Extensions != nil {
			for n, v := range ceOverrides.Extensions {
				event.SetExtension(n, v)
			}
		}

		if err := event.SetData(cloudevents.ApplicationJSON, hb); err != nil {
			log.Printf("failed to set cloudevents data: %s", err.Error())
		}

		log.Printf("sending cloudevent to %s", sink)
		if res := c.Send(context.Background(), event); !cloudevents.IsACK(res) {
			log.Printf("failed to send cloudevent: %v", res)
		}

		if env.OneShot {
			return
		}

		// Wait for next tick
		<-ticker.C
	}
}

The following is an example of a container source that references the previous heartbeats container image:

apiVersion: sources.knative.dev/v1
kind: ContainerSource
metadata:
  name: test-heartbeats
spec:
  template:
    spec:
      containers:
        # This corresponds to a heartbeats image URI that you have built and published
        - image: gcr.io/knative-releases/knative.dev/eventing/cmd/heartbeats
          name: heartbeats
          args:
            - --period=1
          env:
            - name: POD_NAME
              value: "example-pod"
            - name: POD_NAMESPACE
              value: "event-test"
  sink:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: example-service
...

2.6.2.2. Creating and managing container sources by using the Knative CLI

You can use the kn source container commands to create and manage container sources by using the Knative (kn) CLI. Using the Knative CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Create a container source

$ kn source container create <container_source_name> --image <image_uri> --sink <sink>

Delete a container source

$ kn source container delete <container_source_name>

Describe a container source

$ kn source container describe <container_source_name>

List existing container sources

$ kn source container list

List existing container sources in YAML format

$ kn source container list -o yaml

Update a container source

This command updates the image URI for an existing container source:

$ kn source container update <container_source_name> --image <image_uri>

2.6.2.3. Creating a container source by using the web console

After Knative Eventing is installed on your cluster, you can create a container source by using the web console. Using the OpenShift Container Platform web console provides a streamlined and intuitive user interface to create an event source.

Prerequisites

  • You have logged in to the OpenShift Container Platform web console.
  • The OpenShift Serverless Operator, Knative Serving, and Knative Eventing are installed on your OpenShift Container Platform cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  1. In the Developer perspective, navigate to +Add Event Source. The Event Sources page is displayed.
  2. Select Container Source and then click Create Event Source. The Create Event Source page is displayed.
  3. Configure the Container Source settings by using the Form view or YAML view:

    Note

    You can switch between the Form view and YAML view. The data is persisted when switching between the views.

    1. In the Image field, enter the URI of the image that you want to run in the container created by the container source.
    2. In the Name field, enter the name of the image.
    3. Optional: In the Arguments field, enter any arguments to be passed to the container.
    4. Optional: In the Environment variables field, add any environment variables to set in the container.
    5. In the Sink section, add a sink where events from the container source are routed to. If you are using the Form view, you can choose from the following options:

      1. Select Resource to use a channel, broker, or service as a sink for the event source.
      2. Select URI to specify where the events from the container source are routed to.
  4. After you have finished configuring the container source, click Create.

2.6.2.4. Container source reference

You can use a container as an event source, by creating a ContainerSource object. You can configure multiple parameters when creating a ContainerSource object.

ContainerSource objects support the following fields:

FieldDescriptionRequired or optional

apiVersion

Specifies the API version, for example sources.knative.dev/v1.

Required

kind

Identifies this resource object as a ContainerSource object.

Required

metadata

Specifies metadata that uniquely identifies the ContainerSource object. For example, a name.

Required

spec

Specifies the configuration information for this ContainerSource object.

Required

spec.sink

A reference to an object that resolves to a URI to use as the sink.

Required

spec.template

A template spec for the ContainerSource object.

Required

spec.ceOverrides

Defines overrides to control the output format and modifications to the event sent to the sink.

Optional

Template parameter example

apiVersion: sources.knative.dev/v1
kind: ContainerSource
metadata:
  name: test-heartbeats
spec:
  template:
    spec:
      containers:
        - image: quay.io/openshift-knative/heartbeats:latest
          name: heartbeats
          args:
            - --period=1
          env:
            - name: POD_NAME
              value: "mypod"
            - name: POD_NAMESPACE
              value: "event-test"
  ...

2.6.2.4.1. CloudEvent overrides

A ceOverrides definition provides overrides that control the CloudEvent’s output format and modifications sent to the sink. You can configure multiple fields for the ceOverrides definition.

A ceOverrides definition supports the following fields:

FieldDescriptionRequired or optional

extensions

Specifies which attributes are added or overridden on the outbound event. Each extensions key-value pair is set independently on the event as an attribute extension.

Optional

Note

Only valid CloudEvent attribute names are allowed as extensions. You cannot set the spec defined attributes from the extensions override configuration. For example, you can not modify the type attribute.

CloudEvent Overrides example

apiVersion: sources.knative.dev/v1
kind: ContainerSource
metadata:
  name: test-heartbeats
spec:
  ...
  ceOverrides:
    extensions:
      extra: this is an extra attribute
      additional: 42

This sets the K_CE_OVERRIDES environment variable on the subject:

Example output

{ "extensions": { "extra": "this is an extra attribute", "additional": "42" } }

2.7. Connecting an event source to a sink using the Developer perspective

When you create an event source by using the OpenShift Container Platform web console, you can specify a sink that events are sent to from that source. The sink can be any addressable or callable resource that can receive incoming events from other resources.

2.7.1. Connect an event source to a sink using the Developer perspective

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving, and Knative Eventing are installed on your OpenShift Container Platform cluster.
  • You have logged in to the web console and are in the Developer perspective.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have created a sink, such as a Knative service, channel or broker.

Procedure

  1. Create an event source of any type, by navigating to +Add Event Source and selecting the event source type that you want to create.
  2. In the Sink section of the Create Event Source form view, select your sink in the Resource list.
  3. Click Create.

Verification

You can verify that the event source was created and is connected to the sink by viewing the Topology page.

  1. In the Developer perspective, navigate to Topology.
  2. View the event source and click the connected sink to see the sink details in the right panel.
Red Hat logoGithubRedditYoutubeTwitter

Learn

Try, buy, & sell

Communities

About Red Hat Documentation

We help Red Hat users innovate and achieve their goals with our products and services with content they can trust.

Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. For more details, see the Red Hat Blog.

About Red Hat

We deliver hardened solutions that make it easier for enterprises to work across platforms and environments, from the core datacenter to the network edge.

© 2024 Red Hat, Inc.