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Resource

Resource event-source watches change notifications for K8s object and helps sensor trigger the workloads.

Event Structure

The structure of an event dispatched by the event-source over the eventbus looks like following,

    {
        "context": {
          "type": "type_of_event_source",
          "specversion": "cloud_events_version",
          "source": "name_of_the_event_source",
          "id": "unique_event_id",
          "time": "event_time",
          "datacontenttype": "type_of_data",
          "subject": "name_of_the_configuration_within_event_source"
        },
        "data": {
          "type": "type_of_the_event", // ADD, UPDATE or DELETE
          "body": "resource_body", // JSON format
          "group": "resource_group_name",
          "version": "resource_version_name",
          "resource": "resource_name"
        }
    }

Specification

Resource event-source specification is available here.

Setup

  1. Create the event source by running the following command.

    kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/event-sources/resource.yaml

  2. Create the sensor by running the following command.

    kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/sensors/resource.yaml

  3. The event source we created in step 1 contains configuration which makes the event-source listen to Argo workflows marked with label app: my-workflow.

  4. Lets create a workflow called my-workflow with label app: my-workflow.

    apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  name: my-workflow
  labels:
    app: my-workflow
spec:
  entrypoint: whalesay
  templates:
  - name: whalesay
    container:
      image: docker/whalesay:latest
      command: [cowsay]
      args: ["hello world"]

  5. Once the my-workflow is created, the sensor will trigger the workflow. Run argo list to list the triggered workflow.

List Options

The Resource Event-Source allows to configure the list options through labels and field selectors for setting up a watch on objects.

In the example above, we had set up the list option as follows,

    filter:
    # labels and filters are meant to provide K8s API options to filter the object list that are being watched.
    # Please read https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#api for more details.

        # labels provide listing options to K8s API to watch objects
        labels:
          - key: app
            # Supported operations like ==, !=, etc.
            # Defaults to ==.
            # Refer https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors for more info.
            # optional.
            operation: "=="
            value: my-workflow

The key-operation-value items under the filter -> labels are used by the event-source to filter the objects that are eligible for the watch. So, in the present case, the event-source will set up a watch for those objects who have label "app: my-workflow". You can add more key-operation-value items to the list as per your use-case.

Similarly, you can pass field selectors to the watch list options, e.g.,

  filter:
    # labels and filters are meant to provide K8s API options to filter the object list that are being watched.
    # Please read https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#api for more details.

    # fields provide listing options to K8s API to watch objects
    fields:
      - key: metadata.name
        # Supported operations like ==, !=, <=, >= etc.
        # Defaults to ==.
        # Refer https://kubernetes.io/docs/concepts/overview/working-with-objects/field-selectors/ for more info.
        # optional.
        operation: ==
        value: my-workflow

Note: The label and fields under filter are used at the time of setting up the watch by the event-source. If you want to filter the objects based on the annotations or some other fields, use the Data Filters available in the sensor.

Troubleshoot

Please read the FAQ.

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