Chapter 4. Brokers

Verification

1. Use the kn command to list all existing brokers:

   $ kn broker list

   You get an output similar to the following example:

   NAME      URL                                                                     AGE   CONDITIONS   READY   REASON
   default   http://broker-ingress.knative-eventing.svc.cluster.local/test/default   45s   5 OK / 5     True

2. Optional: If you are using the OpenShift Container Platform web console, you can navigate to the Topology view and observe that the broker exists:

   

Procedure

1. Create a Trigger object as a YAML file that has the eventing.knative.dev/injection: enabled annotation:

   apiVersion: eventing.knative.dev/v1
   kind: Trigger
   metadata:
     annotations:
       eventing.knative.dev/injection: enabled
     name: <trigger_name>
   spec:
     broker: default
     subscriber: 

   1

   
       ref:
         apiVersion: serving.knative.dev/v1
         kind: Service
         name: <service_name>

   1 1

   Specify details about the event sink, or subscriber, that the trigger sends events to.

2. Apply the Trigger YAML file:

   $ oc apply -f <filename>

1. Enter the following oc command to get the broker:

   $ oc -n <namespace> get broker default

   Example output

   NAME      READY     REASON    URL                                                                     AGE
   default   True                http://broker-ingress.knative-eventing.svc.cluster.local/test/default   3m56s

2. Optional: If you are using the OpenShift Container Platform web console, you can navigate to the Topology view and observe that the broker exists:

   

1. Use the oc command to get the broker:

   $ oc -n <namespace> get broker <broker_name>

   You get an output similar to the following example command:

   $ oc -n default get broker default

   You get an output similar to the following example:

   NAME      READY     REASON    URL                                                                     AGE
   default   True                http://broker-ingress.knative-eventing.svc.cluster.local/test/default   3m56s

2. Optional: If you are using the OpenShift Container Platform web console, you can navigate to the Topology view and observe that the broker exists:

   

Procedure

1. Remove the eventing.knative.dev/injection=enabled label from the namespace:

   $ oc label namespace <namespace> eventing.knative.dev/injection-

   Removing the annotation prevents Knative from recreating the broker after you delete it.

2. Delete the broker from the selected namespace:

   $ oc -n <namespace> delete broker <broker_name>

Procedure

1. Navigate to +Add Broker. The Broker page is displayed.
2. Optional. Update the Name of the broker. If you do not update the name, the system names the generated broker default.
3. Click Create.

Verification

1. Verify broker creation by viewing broker components on the Topology page.
2. Navigate to Topology.

3. View the mt-broker-ingress, mt-broker-filter, and mt-broker-controller components.

   

Procedure

1. Change the KnativeEventing custom resource (CR) to add configuration details for the config-br-default-channel config map:

   apiVersion: operator.knative.dev/v1beta1
   kind: KnativeEventing
   metadata:
     name: knative-eventing
     namespace: knative-eventing
   spec:
     config:
       config-br-default-channel:
         channel-template-spec: |
           apiVersion: messaging.knative.dev/v1beta1
           kind: KafkaChannel
           spec:
             numPartitions: 6
             replicationFactor: 3

2. Apply the updated KnativeEventing CR by running the following command::

   $ oc apply -f <filename>

Procedure

1. Modify the KnativeEventing custom resource to add configuration details for the config-br-defaults config map:

   apiVersion: operator.knative.dev/v1beta1
   kind: KnativeEventing
   metadata:
     name: knative-eventing
     namespace: knative-eventing
   spec:
     defaultBrokerClass: Kafka
     config:
       config-br-defaults:
         default-br-config: |
           clusterDefault:
             brokerClass: Kafka
             apiVersion: v1
             kind: ConfigMap
             name: kafka-broker-config
             namespace: knative-eventing
           namespaceDefaults:
             my-namespace:
               brokerClass: MTChannelBasedBroker
               apiVersion: v1
               kind: ConfigMap
               name: config-br-default-channel
               namespace: knative-eventing
   ...

   • defaultBrokerClass: Kafka: The default broker class for Knative Eventing.
   • In spec.config, specify the config maps to change.
   • config-br-defaults: The config-br-defaults config map defines default settings for brokers without explicit configuration.
   • clusterDefault: The cluster-wide default broker class configuration.
   • name: kafka-broker-config: The kafka-broker-config config map defines default Kafka broker settings.
   • namespace: knative-eventing: The namespace where the kafka-broker-config config map exists.
   • namespaceDefaults: The namespace-specific default broker class configuration.
   • name: config-br-default-channel: The config-br-default-channel config map defines the default backing channel.
   • namespace: knative-eventing: The namespace where the config-br-default-channel config map exists.
   Important

   Namespace-specific defaults override cluster-wide settings.

2. Apply the updated KnativeEventing custom resource by running the following command:

   $ oc apply -f <filename>

Procedure

1. Change the kafka-broker-config config map, or create your own config map that has the following configuration:

   apiVersion: v1
   kind: ConfigMap
   metadata:
     name: <config_map_name>
     namespace: <namespace>
   data:
     default.topic.partitions: <integer>
     default.topic.replication.factor: <integer>
     bootstrap.servers: <list_of_servers>
     default.topic.config.<config_option>: <value>

   • name: <config_map_name>: The config map name.
   • namespace: <namespace>: The namespace where the config map exists.
   • default.topic.partitions: <integer>: The number of topic partitions for the Kafka broker. This controls how quickly events can be sent to the broker. A higher number of partitions requires greater compute resources.
   • default.topic.replication.factor: <integer>: The replication factor of topic messages. This prevents against data loss. A higher replication factor requires greater compute resources and more storage.
   • bootstrap.servers: <list_of_servers>: A comma-separated list of bootstrap servers. This can be inside or outside of the OpenShift Container Platform cluster, and is a list of Kafka clusters that the broker receives events from and sends events to.
   • default.topic.config.<config_option>: A topic config option.
   Important

   The default.topic.replication.factor value must be less than or equal to the number of Kafka broker instances in your cluster. For example, if you only have one Kafka broker, the default.topic.replication.factor value should not be more than "1".

   The following example displays Kafka broker config map:

   apiVersion: v1
   kind: ConfigMap
   metadata:
     name: kafka-broker-config
     namespace: knative-eventing
   data:
     default.topic.partitions: "10"
     default.topic.replication.factor: "3"
     bootstrap.servers: "my-cluster-kafka-bootstrap.kafka:9092"
     default.topic.config.retention.ms: "3600"

2. Apply the config map by running the following command:

   $ oc apply -f <config_map_filename>

3. Specify the config map for the Kafka Broker object:

   apiVersion: eventing.knative.dev/v1
   kind: Broker
   metadata:
     name: <broker_name>
     namespace: <namespace>
     annotations:
       eventing.knative.dev/broker.class: Kafka
   spec:
     config:
       apiVersion: v1
       kind: ConfigMap
       name: <config_map_name>
       namespace: <namespace>
   ...

4. Apply the broker by running the following command:

   $ oc apply -f <broker_filename>

Procedure

1. In the Topology view, point to the broker that you have created. An arrow is displayed. Drag the arrow to the sink that you want to connect to the broker. This action opens the Add Trigger dialog box.
2. In the Add Trigger dialog box, enter a name for the trigger and click Add.

Verification

1. Verify that the broker connects to the sink by viewing the Topology page.
2. Navigate to Topology.
3. Click the line that connects the broker to the sink to see details about the trigger in the Details panel.