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59 lines
2.1 KiB
Plaintext
59 lines
2.1 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * serverless/event_workflows/serverless-channels.adoc
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[id="serverless-inmemorychannel_{context}"]
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= Using the default development channel configuration
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When you install Knative Eventing, the following `default-ch-webhook` config map is created automatically in the `knative-eventing` namespace:
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[source,yaml]
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----
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: default-ch-webhook
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namespace: knative-eventing
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data:
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default-ch-config: |
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clusterDefault:
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apiVersion: messaging.knative.dev/v1
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kind: InMemoryChannel
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namespaceDefaults:
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some-namespace:
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apiVersion: messaging.knative.dev/v1
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kind: InMemoryChannel
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----
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This config map can specify either a cluster-wide default channel implementation, or a namespace-specific default channel implementation.
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Configuring a namespace-specific default overrides any cluster-wide settings.
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After you create a `Channel` object, a mutating admission webhook adds a set of `spec.channelTemplate` properties for the `Channel` object based on the default channel implementation.
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.Example `Channel` object with `spec.channelTemplate` properties
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[source,yaml]
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----
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apiVersion: messaging.knative.dev/v1
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kind: Channel
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metadata:
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name: example-channel
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namespace: default
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spec:
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channelTemplate:
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apiVersion: messaging.knative.dev/v1
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kind: InMemoryChannel
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----
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The channel controller then creates the backing channel instance based on the `spec.channelTemplate` configuration.
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[NOTE]
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====
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The `spec.channelTemplate` properties cannot be changed after creation, because they are set by the default channel mechanism rather than by the user.
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====
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When this mechanism is used, two objects are created: a generic channel, and an `InMemoryChannel` channel.
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The generic channel acts as a proxy that copies its subscriptions to the `InMemoryChannel` channel, and sets its status to reflect the status of the backing `InMemoryChannel` channel.
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Because the channel in this example is created in the default namespace, the channel uses the cluster default, which is InMemoryChannel.
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