eventing config-br-defaults set delivery spec defaults

[runzexia]

Describe the change you'd like to see
add docs about how to set delivery spec defaults by changing config-br-defaults

Additional context
knative/eventing#4172
knative/eventing#4328

[xtreme-sameer-vohra]

Would it be possible to automate this based on the the schema, like this tool allows ?

[github-actions]

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[abrennan89]

Requires updates to the docs here: https://knative.dev/development/admin/eventing/broker-configuration/

[pierDipi]

I'm adding more details to this issue.

On this page https://knative.dev/docs/eventing/configuration/broker-configuration/
users can configure some Broker defaults cluster-wide or per namespace.
For example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: config-br-defaults
  namespace: knative-eventing
  labels:
    eventing.knative.dev/release: devel
data:
  # Configures the default for any Broker that does not specify a spec.config or Broker class.
  default-br-config: |
    clusterDefault:
      brokerClass: MTChannelBasedBroker
      apiVersion: v1
      kind: ConfigMap
      name: config-kafka-channel
      namespace: knative-eventing
    namespaceDefaults:
      namespace-1:
        apiVersion: v1
        kind: ConfigMap
        name: config-br-default-channel
        namespace: knative-eventing

With the new feature, another field called delivery can be configured as well, as follows:

apiVersion: v1
kind: ConfigMap
metadata:
  name: config-br-defaults
  namespace: knative-eventing
  labels:
    eventing.knative.dev/release: devel
data:
  # Configures the default for any Broker that does not specify a spec.config or Broker class.
  default-br-config: |
    clusterDefault:
      brokerClass: MTChannelBasedBroker
      apiVersion: v1
      kind: ConfigMap
      name: config-kafka-channel
      namespace: knative-eventing
      delivery:
        retry: 10
        backoffDelay: PT0.2S
        backoffPolicy: exponential
    namespaceDefaults:
      namespace-1:
        apiVersion: v1
        kind: ConfigMap
        name: config-br-default-channel
        namespace: knative-eventing
        delivery:
          deadLetterSink:
            ref:
              kind: Service
              namespace: example-namespace
              name: example-service
              apiVersion: v1
            uri: example-uri
          retry: 10
          backoffPolicy: exponential
          backoffDelay: "PT0.2S" 

The delivery field has the same shape as the delivery field of the broker as shown on this page https://knative.dev/docs/eventing/broker/example-mtbroker/:

# ...
 spec:
   # ...
   delivery:
     deadLetterSink:
       ref:
         kind: Service
         namespace: example-namespace
         name: example-service
         apiVersion: v1
       uri: example-uri
     retry: 10
     backoffPolicy: exponential
     backoffDelay: "PT0.2S"

[pierDipi]

let me know if the above helps!

[abrennan89]

Thank you so much @pierDipi ! This is great!

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.

[pierDipi]

/remove-lifecycle stale