Allow addons to be installed by label, but also manually

[tesshuflower]

Describe the enhancement

I'm considering this an enhancement request, but we do have some functionality that was removed between v0.9.0 and v0.10.0 of the addon-framework.

Essentially my use-case (for the ACM volsync-addon-controller which uses the addon-framework) is that users are able to deploy the addon to managed clusters in 2 ways:

1. Users can add a specific label to a ManagedCluster resource, and then the ManagedClusterAddOn resource is created automatically for them in the managedcluster namespace on the hub.
2. Users can manually create the ManagedClusterAddOn.

This has been the case for quite a few ACM releases.

To achieve this, I have the following in my addon setup:

agent.AgentAddonOptions{
		AddonName: addonName,
		InstallStrategy: agent.InstallByLabelStrategy(
			"",
			metav1.LabelSelector{
				MatchLabels: map[string]string{
					ManagedClusterInstallVolSyncLabel: ManagedClusterInstallVolSyncLabelValue,
				},
			},
		),

but now in v0.10.0 the InstallByLabelStrategy has been removed.

Is there something I can do to get this functionality back? For the meantime I'm not updating to the addon-framework v0.10.0.

[haoqing0110]

cc @qiujian16
Seems currently with v0.10.0, we can support case 1 (cma spec.installStrategy.type is "Placements") or case 2 (cma spec.installStrategy.type is"Manual"), but not 1 & 2 at the same time. When installStrategy type is Placements, the manually created mca will be removed.

[tesshuflower]

I'm not sure I understand the "Placements" install strategy - will this work for a label? Or would someone need to create a placement that then looks for a label selector?

[haoqing0110]

@tesshuflower

With "Placements" install strategy, you will need to create 2 resources as below, 1 cma and 1 placement with label selector.
With this defined, the user can no longer manually create mca unless changes the type to Manual.

apiVersion: addon.open-cluster-management.io/v1alpha1
kind: ClusterManagementAddOn
metadata:
  name: helloworld
  annotations:
    addon.open-cluster-management.io/lifecycle: "addon-manager"
spec:
  addOnMeta:
    displayName: helloworld
  installStrategy:
    type: Placements
    placements:
    - name: placement-test
      namespace: default

apiVersion: cluster.open-cluster-management.io/v1beta1
kind: Placement
metadata:
  name: placement-test
  namespace: default
spec:
  predicates:
    - requiredClusterSelector:
        labelSelector:
          matchLabels:
            purpose: test

[tesshuflower]

I think this also breaks my current scenario where I have already allowed customers to deploy via setting a specific label on their managedclusters - now they would have to create those resources in order to be able to use a label selector (or I would need to always create the CMA & placement myself - which could be problematic if they already have their own CMA with other settings).

[haoqing0110]

@tesshuflower yes, this is indeed the "expected" breaking changes when upgrading to v0.10.0. Another option to keep the current user behavior while upgrading to v0.10.0 might be to set installStrategy type as Manual, and implement your own controller to install the mca.