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eventlisteners.md

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EventListener

EventListeners connect TriggerBindings to TriggerTemplates and provide an addressable endpoint, which is where webhooks/events are directed. This is also where the service account is connected, which specifies what permissions the resources will be created (or at least attempted) with. Note that currently, JSON is the only accepted MIME type for events.

When an EventListener is successfully created, a service is created that references a listener pod. This listener pod accepts the incoming events and does what has been specified in the corresponding TriggerBindings/TriggerTemplates. The created service is by default of type ClusterIP; any other pods running in the same Kubernetes cluster can access services' via their cluster DNS. For external services to connect to your cluster (e.g. GitHub sending webhooks), check out the guide on exposing eventlisteners

Parameters

EventListeners can provide params which are merged with the TriggerBinding params and passed to the TriggerTemplate. Each parameter has a name and a value.

EventListener spec.serviceType can be set to ClusterIP (default) | NodePort | LoadBalancer to configure the underlying Service resource to make it reachable externally.

Event Interceptors

Triggers within an EventListener can optionally specify an interceptor field which contains an ObjectReference to a Kubernetes Service. If an interceptor is specified, the EventListener sink will forward incoming events to the service referenced by the interceptor over HTTP. The service is expected to process the event and return a response back. The status code of the response determines if the processing is successful and the returned body is used as the new event payload by the EventListener and passed on the TriggerBinding. An interceptor has an optional header field with key-value pairs that will be merged with event headers before being sent; canonical names must be specified.

Event Interceptor Services

To be an Event Interceptor, a Kubernetes object should:

  • Be fronted by a regular Kubernetes v1 Service over port 80
  • Accept JSON payloads over HTTP
  • Return a HTTP 200 OK Status if the EventListener should continue processing the event
  • Return a JSON body back. This will be used by the EventListener as the event payload for any further processing. If the interceptor does not need to modify the body, it can simply return the body that it received.
apiVersion: tekton.dev/v1alpha1
kind: EventListener
metadata:
  name: listener-interceptor
spec:
  serviceAccountName: tekton-triggers-example-sa
  triggers:
    - name: foo-trig
      interceptor:
        header:
        - name: Foo-Trig-Header1
          value: string-value
        - name: Foo-Trig-Header2
          value:
          - array-val1
          - array-val2
        objectRef:
          kind: Service
          name: gh-validate
          apiVersion: v1
          namespace: default
      binding:
        name: pipeline-binding
      template:
        name: pipeline-template
      params:
      - name: message
        value: Hello from the Triggers EventListener!