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helmAgentAddon.md

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helmAgentAddon.md

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Overview

This doc is used to introduce how to migrate Helm Chart to an AddOn.

Limitations

  1. Not all of built-in Objects of Helm Chart are support in AddOn. We only support below:
  • Capabilities.KubeVersion.Version
  • Release.Name
  • Release.Namespace
  1. Not support Hooks of Helm Chart currently.

Migration

We have an example for Helm Chart migration in helloworld_helm.

  1. Need to import Helm Chart files into embed.FS.
  2. Create and start helmAgentAddon instance like this: 
    mgr, err := addonmanager.New(controllerContext.KubeConfig)
 if err != nil {
 	return err
 }

 agentAddon, err := addonfactory.NewAgentAddonFactory(addonName, FS, "manifests/charts/helloworld").
 	WithGetValuesFuncs(getValues, addonfactory.GetValuesFromAddonAnnotation).
 	WithAgentRegistrationOption(registrationOption).
 	BuildHelmAgentAddon()
 if err != nil {
 	return err
 }

 mgr.AddAgent(agentAddon)
 mgr.Start(ctx)

Values definition

Built-in values

AddOn built-in values

  • Value.clusterName
  • Value.addonInstallNamespace
  • Value.hubKubeConfigSecret (used when the AddOn is needed to register to the Hub cluster)

Helm Chart built-in values

  • Capabilities.KubeVersion is the ManagedCluster.Status.Version.Kubernetes.
  • Release.Name is the AddOn name.
  • Release.Namespace is the addonInstallNamespace.

In the list of GetValuesFuncs, the values from the big index Func will override the one from low index Func. The built-in values will override the values got from the list of GetValuesFuncs.

The Variable names in Values should begin with lowercase. So the best practice is to define a json struct for the values, and convert it to Values using the JsonStructToValues.

Values from annotation of ManagedClusterAddon

We support a helper GetValuesFunc named GetValuesFromAddonAnnotation which can get values from annotation of ManagedClusterAddon. The key of the Helm Chart values in annotation is addon.open-cluster-management.io/values, and the value should be a valid json string which has key-value format.