Announcing extended support for minor Kubernetes versions in AKS hybrid

We are excited to announce that AKS hybrid will now support minor Kubernetes versions for 1 year starting with v1.23.x. This was in response to feedback from customers emphasizing preference for consistency in the support of minor Kubernetes version with AKS in Azure, we have made changes to make this possible.

What have we changed?

1. Support updates to next minor version

In the past, updating an AKS cluster required workload clusters to be operating on a patch version that would also be supported in the new release. For instance, if you were running on v1.22.11 in January and a new release in February deprecated v1.22.11, you would be prompted to first upgrade the workload cluster to a version supported in February before updating the management cluster. This constraint has been removed in v1.0.18.* release, allowing you to update the management cluster even when the workload cluster patch version has been deprecated. However, this will only be feasible if the minor version remains within the support window. If the workload cluster minor version falls outside the support window by more than two minor versions, the update will be restricted as the cluster will no longer be eligible for support and will lose any possibility of regaining support once the update is initiated. This improvement will benefit customers who maintain a given minor version for extended periods, as it will make upgrading to a new version considerably more seamless and expedited while eliminating complexities experienced in previous iterations.

Important: Removing  this constraint implies that, in some instances, you will not be able to perform OS patches for workload clusters. To get latest OS patches, we recommend you upgrade the minor version or manually execute the 'sudo update' command within each worker node virtual machine to patch the nodes.

2. More flexibility when step upgrading to the latest release

We have also incorporated an enhancement that allows users to skip releases during the update process, which will expedite the process and improve efficiency. This enhancement means that updates will still be executed in a stepped manner required by the Kubernetes version skew policy, but the process will perform jumps where it makes sense to. This change ensures a smoother and faster transition to the latest release, and hence saving hours spent during the updates.

3. Support policy changes

With this change, we have also updated our to reflect this new state of the world. Below are key things to note:

• Microsoft offers a support window of one year for each Kubernetes minor version, commencing from the initial date AKS hybrid shipped the minor version. During this period, AKS hybrid will release subsequent minor or patch versions to ensure ongoing support.
• An AKS hybrid cluster that is operating on a deprecated minor version will have to be updated to a supported version to be eligible for support.
• Once a minor version has been deprecated, any clusters still running on this version will continue to function; you will be able to perform operations such as scaling up or down but will have a warning displayed during cluster operations.
• Once a minor version has been deprecated, it will be removed from the Microsoft servers. At that point AKS hybrid clusters using this version will not be able to update Kubernetes or OS versions and will have to be upgraded to the latest release. In some cases this can also mean full re-deployment if the system is not in a healthy state.

4. New commandlet 'Test-AksHciUpdate' 

We are pleased to announce the addition of a new PowerShell cmdlet, Test-AksHciUpdate that will assist in determining if target clusters are operating on minor versions outside the support window.