Channel based Broker¶

The Channel based Broker (MTChannelBasedBroker) uses Channels for event routing. It is shipped by default with Knative Eventing. Users should prefer native Broker implementations (like Knative Broker for Apache Kafka or RabbitMQ Broker) over the MTChannelBasedBroker and Channel combination because it is usually more efficient as they reduce network hops for example.

Prerequisites¶

You have Knative Eventing installed.
You have a Channel implementation installed.

As the MTChannelBasedBroker is based on Channels, you need to install a Channel implementation. Check out the available Channels for a (non-exhaustive) list of the available Channels for Knative Eventing.

You can install for example the InMemory Channel by running the following command:

kubectl apply -f https://storage.googleapis.com/knative-nightly/eventing/latest/in-memory-channel.yaml

Create a MTChannelBasedBroker¶

You can create a MTChannelBasedBroker by using the kn CLI or by applying YAML files using kubectl.

knkubectl

You can create a MTChannelBasedBroker by entering the following command:

kn broker create <broker-name> --class MTChannelBasedBroker

Where <broker-name> is the name of your Broker.

The YAML in the following example creates a Broker.

Create a MTChannelBasedBroker by creating a YAML file using the following template:
```
apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
  annotations:
    eventing.knative.dev/broker.class: MTChannelBasedBroker
  name: <broker-name>
```
Where <broker-name> is the name of your Broker.

Note

Note, that the Broker class is specified via the eventing.knative.dev/broker.class annotation.
Apply the YAML file:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Configuration¶

You configure the Broker object itself, or you can define cluster or namespace default values.

Broker specific configuration¶

It is possible to configure each Broker individually by referencing a ConfigMap in the spec.config:

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: my-broker-specific-configuration
    namespace: default

The referenced ConfigMap must contain a channel-template-spec that defines the underlining Channel implementation for this Broker, as well as some Channel specific configurations. For example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-broker-specific-configuration
  namespace: default
data:
  channel-template-spec: |
    apiVersion: messaging.knative.dev/v1
    kind: InMemoryChannel

Kafka Channel configuration example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: kafka-channel
  namespace: knative-eventing
data:
  channel-template-spec: |
    apiVersion: messaging.knative.dev/v1beta1
    kind: KafkaChannel
    spec:
      numPartitions: 3
      replicationFactor: 1

Broker default configuration¶

The config-br-defaults ConfigMap defines default values for any Broker that does not specify a spec.config or a Broker class. It is possible to define these defaults cluser wide or on a per namespace basis. Check the Administrator configuration options on how to set Broker defaults cluster wide or on a namespace basis.

Developer documentation¶

For more information about MTChannelBasedBroker, see the MTChannelBasedBroker developer documentation.