Context Filter¶

Context filter is applied to the event context. A CloudEvent from Webhook event-source has payload structure as:

{
    "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": {
      "header": {},
      "body": {},
    }
}

Fields¶

Context filter has following fields:

filters:
  context:
    type: event_type
    subject: event_subject
    source: event_source
    datacontenttype: event_data_content_type

You can also specify id, specversion and time fields in the YAML manifest, but they are ignored in filtering.

Note It could be useless to build a context filter based on datacontenttype, source and subject as currently they come fixed from event-source:

datacontenttype is always application/json
source corresponds to eventSourceName specified in the Sensor YAML manifest
subject corresponds to eventName specified in the Sensor YAML manifest

How it works¶

Specify one or more of the available context fields:

apiVersion: argoproj.io/v1alpha1
kind: Sensor
metadata:
  name: with-ctx-filter
spec:
  template:
    serviceAccountName: operate-workflow-sa
  dependencies:
    - name: test-dep
      eventSourceName: webhook
      eventName: example
      filters:
        context:
          source: custom-webhook

Practical example¶

Create a webhook event-source

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

Create a webhook sensor with context filter

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

Send an HTTP request to event-source

curl -d '{"message":"this is my first webhook"}' -H "Content-Type: application/json" -X POST http://localhost:12000/example

You will notice in sensor logs that the event is invalid as the sensor expects custom-webhook as the value of the source

Further examples¶

You can find some examples here.