Sink

A sink is an Addressable resource that acts as a link between the Eventing mesh and an entity or system.

We can connect any source to a sink, such as PingSource and KafkaSink objects:

apiVersion: sources.knative.dev/v1beta1
kind: PingSource
metadata:
  name: test-ping-source
spec:
  schedule: "*/1 * * * *"
  jsonData: '{"message": "Hello world!"}'
  sink:
    ref:
      apiVersion: eventing.knative.dev/v1alpha1
      kind: KafkaSink
      name: my-kafka-sink

We can connect a Trigger object to a sink, so that we can filter events, before sending them to a sink:

apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: my-service-trigger
spec:
  broker: default
  filter:
    attributes:
      type: dev.knative.foo.bar
      myextension: my-extension-value
  subscriber:
    ref:
      apiVersion: eventing.knative.dev/v1alpha1
      kind: KafkaSink
      name: my-kafka-sink

Setting up a Custom Resource to be used as a sink

To allow a Custom Resource to act as a sink for events, there are two things needed:

1. Make the resource Addressable

To make a Custom Resource Addressable, it needs to contain a status.address.url. More information about Addressable resources.

2. Create an addressable-resolver ClusterRole

An addressable-resolver ClusterRole is needed in order to obtain the necessary RBAC rules for the sink to receive events.

For example, we can create a kafkasinks-addressable-resolver ClusterRole to allow get, list, and watch access to kafkasinks and kafkasinks/status

kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: kafkasinks-addressable-resolver
  labels:
    kafka.eventing.knative.dev/release: devel
    duck.knative.dev/addressable: "true"
# Do not use this role directly. These rules will be added to the "addressable-resolver" role.
rules:
  - apiGroups:
      - eventing.knative.dev
    resources:
      - kafkasinks
      - kafkasinks/status
    verbs:
      - get
      - list
      - watch

Knative Sinks

Table of contents

• Apache Kafka Sink