SinkBinding reference
- Supported parameters
  - Subject parameter
    - Subject parameter examples
  - CloudEvent Overrides
    - CloudEvent Overrides example

SinkBinding reference

This topic provides reference information about the configurable parameters for SinkBinding objects.

Supported parameters

A SinkBinding resource supports the following parameters:

Field	Description	Required 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	A reference to 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

Subject parameter

The Subject parameter references the resources for which the “runtime contract” is augmented by Binding implementations.

A subject definition supports the following fields:

Field	Description	Required 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 object holding it.	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. The requirements are ANDed.	Use one of `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 `operator` is `In` or `NotIn`, the values array must be non-empty. If `operator` 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.“. The requirements are ANDed.	Use one of `matchExpressions` or `matchLabels`

Subject parameter examples

Given the following YAML, the Deployment 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 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/v1beta1
    kind: Job
    namespace: default
    selector:
      matchLabels:
        working: example
  ...

Given the following YAML, any Pod 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
  ...

CloudEvent Overrides

CloudEvent Overrides defines overrides to control the output format and modifications of the event sent to the sink.

A ceOverrides definition supports the following fields:

Field	Description	Required 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

Contract

This results in the K_CE_OVERRIDES environment variable being set on the subject as follows:

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