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Rolling upgrade is an important feature a user may want for a managed Kubernetes service.
Note
Kubernetes version upgrade is only supported by the Fedora Atomic and the Fedora CoreOS drivers.
A user can run a command as shown below to trigger a rolling ugprade for Kubernetes version upgrade or node operating system version upgrade.
openstack coe cluster upgrade <cluster ID> <new cluster template ID>The key parameter in the command is the new cluster template ID. For Kubernetes version upgrade, a newer version for label kube_tag should be provided. Downgrade is not supported.
A simple operating system upgrade can be applied using a new image ID in the new cluster template. However, this entails a downtime for applications running on the cluster, because all the nodes will be rebuilt one by one.
The Fedora Atomic driver supports a more gradeful operating system upgrade. Similar to the Kubernetes version upgrade, it will cordon and drain the nodes before upgrading the operating system with rpm-ostree command. There are one of two labels which must be provided to support this feature:
- `ostree_commit`: this is a commit ID of ostree the current system should be upgraded to. An example of a commit ID is 1766b4526f1a738ba1e6e0a66264139f65340bcc28e7045f10cbe6d161eb1925,
- `ostree_remote`: this is a remote name of ostree the current system should be rebased to. An example of a remote name is fedora-atomic:fedora/29/x86_64/atomic-host.
If both labels are present, ostree_commit takes precedence. To check if there are updates available, run sudo rpm-ostree upgrade --check on the Atomic host which will show you the latest commit ID that can be upgraded to.