Configure Broker defaults¶

Knative Eventing provides a config-br-defaults ConfigMap that contains the configuration settings that govern default Broker creation.

The default config-br-defaults ConfigMap is 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-br-default-channel
      namespace: knative-eventing

Channel implementation options¶

The following example shows a Broker object where the spec.config configuration is specified in a config-br-default-channel ConfigMap:

apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
  annotations:
    eventing.knative.dev/broker.class: MTChannelBasedBroker
  name: default
spec:
  # Configuration specific to this broker.
  config:
    apiVersion: v1
    kind: ConfigMap
    name: config-br-default-channel
    namespace: knative-eventing

A Broker object that does not have a spec.config specified uses the config-br-default-channel ConfigMap dy default because this is specified in the config-br-defaults ConfigMap.

However, if you have installed a different Channel implementation, for example, Kafka, and would like this to be used as the default Channel implementation for any Broker that is created, you can change the config-br-defaults ConfigMap to look 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: kafka-channel
      namespace: knative-eventing

Now every Broker created in the cluster that does not have a spec.config will be configured to use the kafka-channel ConfigMap.

For more information about creating a kafka-channel ConfigMap to use with your Broker, see the Kafka Channel ConfigMap documentation.

Changing the default Channel implementation for a namespace¶

You can modify the default Broker creation behavior for one or more namespaces.

For example, if you wanted to use the kafka-channel ConfigMap for all other Brokers created, but wanted to use config-br-default-channel ConfigMap for namespace-1 and namespace-2, you would use the following ConfigMap settings:

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
      namespace-2:
        apiVersion: v1
        kind: ConfigMap
        name: config-br-default-channel
        namespace: knative-eventing

Broker class options¶

When a Broker is created without a specified BrokerClass annotation, the default MTChannelBasedBroker Broker class is used, as specified in the config-br-defaults ConfigMap.

The following example creates a Broker called default in the default namespace, and uses MTChannelBasedBroker as the implementation:

Create a YAML file for your Broker using the following example:

apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
  name: default
  namespace: default

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Configuring the Broker class¶

To configure a Broker class, you can modify the eventing.knative.dev/broker.class annotation and spec.config for the Broker object. MTChannelBasedBroker is the Broker class default.

Modify the eventing.knative.dev/broker.class annotation. Replace MTChannelBasedBroker with the class type you want to use:

apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
  annotations:
    eventing.knative.dev/broker.class: MTChannelBasedBroker
  name: default
  namespace: default

Configure the spec.config with the details of the ConfigMap that defines the backing Channel for the Broker class:

apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
  annotations:
    eventing.knative.dev/broker.class: MTChannelBasedBroker
  name: default
  namespace: default
spec:
  config:
    apiVersion: v1
    kind: ConfigMap
    name: config-br-default-channel
    namespace: knative-eventing

Configuring the default BrokerClass for the cluster¶

You can configure the clusterDefault Broker class so that any Broker created in the cluster that does not have a BrokerClass annotation uses this default class.

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

Configuring the default BrokerClass for namespaces¶

You can modify the default Broker class for one or more namespaces.

For example, if you want to use a KafkaBroker class for all other Brokers created on the cluster, but you want to use the MTChannelBasedBroker class for Brokers created in namespace-1 and namespace-2, you would use the following ConfigMap settings:

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: KafkaBroker
    namespaceDefaults:
      namespace1:
        brokerClass: MTChannelBasedBroker
      namespace2:
        brokerClass: MTChannelBasedBroker