With 0.15 the MTChannelBasedBroker is the new default broker (#2533)

Signed-off-by: Matthias Wessendorf <[email protected]>

Author: matzew

docs/eventing/broker/README.md

@@ -13,7 +13,7 @@ There can be different classes of Brokers providing different kinds
 of semantics around durability of events, performance, etc. The Broker that is
 part of the Knative Eventing repo is used for these examples, it uses Knative
 [Channels](../channels/) for delivering events. You can read more details about
-[Channel Based Broker](./channel-based-broker.md). Simple example showing a `Broker`
+[MT Channel Based Broker](./mt-channel-based-broker.md). Simple example showing a `Broker`
 where the configuration is specified in a `ConfigMap` config-br-default-channel,
 which uses `InMemoryChannel`:
 
@@ -112,7 +112,7 @@ have the extension `myextension` with the value `my-extension-value`.
 ### Broker setup
 
 We assume that you have installed a Broker in namespace `default`. If you haven't done that
-yet, [install it from here](./channel-based-broker.md).
+yet, [install it from here](./mt-channel-based-broker.md).
 
 ### Subscriber
 

docs/eventing/broker/channel-based-broker.md

@@ -145,4 +145,64 @@ spec:
 EOF
 ```
 
+## Creating Broker by Annotation
+
+The easiest way to get Broker installed, is to annotate your namespace
+(replace `default` with the desired namespace):
+
+```shell
+kubectl label namespace default knative-eventing-injection=enabled
+```
+
+This will automatically create a `Broker` named `default` in the `default`
+namespace. As per above configuration, it would be configured to use Kafka
+channels.
+
+```shell
+kubectl -n default get broker default
+```
+
+_NOTE_ `Broker`s created due to annotation will not be removed if you remove the
+annotation. For example, if you annotate the namespace, which will then create
+the `Broker` as described above. If you now remove the annotation, the `Broker`
+will not be removed, you have to manually delete it.
+
+For example, to delete the injected Broker from the foo namespace:
+
+```shell
+kubectl -n foo delete broker default
+```
+
+## Creating Broker by Trigger Annotation
+
+Besides the annotation of the namespace, there is an alternative approach to annotate
+one of the Triggers, with `knative-eventing-injection: enabled`:
+
+```yaml
+apiVersion: eventing.knative.dev/v1beta1
+kind: Trigger
+metadata:
+  annotations:
+    knative-eventing-injection: enabled
+  name: testevents-trigger0
+  namespace: default
+spec:
+  broker: default
+  filter:
+    attributes:
+      type: dev.knative.sources.ping
+  subscriber:
+    ref:
+      apiVersion: serving.knative.dev/v1
+      kind: Service
+      name: broker-display
+```
+
+However, this approach only works _if_ the `Trigger` is coupled to the default `Broker`, and takes only effect
+when there is no default `Broker` already present.
+
+Deleting the `Trigger` does not delete the `Broker`. With this approach the same rules from the
+[namespace annotation](./#installing-broker-by-annotation) apply here.
+
+
 You can find out more about delivery spec details [here](https://knative.dev/docs/eventing/event-delivery/).