Add blog enhanced-extension-management-introducing-autoenable-and-clustercompatibility (gardener#663)

Author: gardener-answering-machine

website/blog/2025/06-18-enhanced-extension-management-introducing-autoenable-and-clustercompatibility.md

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+---
+title: "Enhanced Extension Management: Introducing `autoEnable` and `clusterCompatibility`"
+linkTitle: "Enhanced Extension Management: Introducing `autoEnable` and `clusterCompatibility`"
+newsSubtitle: June 18, 2025
+publishdate: 2025-06-18
+authors:
+- avatar: https://avatars.githubusercontent.com/timuthy
+  login: timuthy
+  name: Tim Usner
+aliases: ["/blog/2025/06/18/enhanced-extension-management-introducing-autoenable-and-clustercompatibility"]
+---
+
+Gardener's extension mechanism has been enhanced with two new fields in the `ControllerRegistration` and `operatorv1alpha1.Extension` APIs, offering operators more granular control and improved safety when managing extensions. These changes, detailed in [PR #11982](https://github.com/gardener/gardener/pull/11982), introduce `autoEnable` and `clusterCompatibility` for resources of `kind: Extension`.
+
+### Fine-Grained Automatic Enablement with `autoEnable`
+
+Previously, operators could use the `globallyEnabled` field to automatically enable an extension resource for all shoot clusters. This field is now deprecated and will be removed in Gardener `v1.123`.
+
+The new `autoEnable` field replaces `globallyEnabled` and provides more flexibility. Operators can now specify an array of cluster types for which an extension should be automatically enabled. The supported cluster types are:
+*   `shoot`
+*   `seed`
+*   `garden`
+
+This allows, for example, an extension to be automatically enabled for all seed clusters or a combination of cluster types, which was not possible with the boolean `globallyEnabled` field.
+
+If `autoEnable` includes `shoot`, it behaves like the old `globallyEnabled: true` for shoot clusters. If an extension is not set to `autoEnable` for a specific cluster type, it must be explicitly enabled in the respective cluster's manifest (e.g., `Shoot` manifest for a shoot cluster).
+
+```yaml
+# Example in ControllerRegistration or operatorv1alpha1.Extension spec.resources
+- kind: Extension
+  type: my-custom-extension
+  autoEnable:
+  - shoot
+  - seed
+  # globallyEnabled: true # This field is deprecated
+```
+
+### Ensuring Correct Deployments with `clusterCompatibility`
+
+To enhance safety and prevent misconfigurations, the `clusterCompatibility` field has been introduced. This field allows extension developers and operators to explicitly define which cluster types a generic Gardener extension is compatible with. The supported cluster types are:
+*   `shoot`
+*   `seed`
+*   `garden`
+
+Gardener will validate that an extension is only enabled or automatically enabled for cluster types listed in its `clusterCompatibility` definition. If `clusterCompatibility` is not specified for an `Extension` kind, it defaults to `['shoot']`. This provides an important safeguard, ensuring that extensions are not inadvertently deployed to environments they are not designed for.
+
+```yaml
+# Example in ControllerRegistration or operatorv1alpha1.Extension spec.resources
+- kind: Extension
+  type: my-custom-extension
+  autoEnable:
+  - shoot
+  clusterCompatibility: # Defines where this extension can be used
+  - shoot
+  - seed
+```
+
+### Important Considerations for Operators
+
+*   **Deprecation of `globallyEnabled`**: Operators should migrate from `globallyEnabled` to the new `autoEnable` field for `kind: Extension` resources. `globallyEnabled` is deprecated and scheduled for removal in Gardener `v1.123`.
+*   **Breaking Change for Garden Extensions**: The introduction of `clusterCompatibility` is a breaking change for operators managing garden extensions via `gardener-operator`. If your `Garden` custom resource specifies `spec.extensions`, you must update the corresponding `operatorv1alpha1.Extension` resources to include `garden` in the `clusterCompatibility` array for those extensions intended to run in the garden cluster.
+
+These new fields provide more precise control over extension lifecycle management across different cluster types within the Gardener ecosystem, improving both operational flexibility and system stability.
+
+For further details, you can review the [original pull request (#11982)](https://github.com/gardener/gardener/pull/11982) and watch the [demonstration in the Gardener Review Meeting (starting at 41:23)](https://youtu.be/HguO_KY86ac?t=2483).