Gardener

Gardener manages the lifecycle of Kubernetes clusters in CobaltCore. It is responsible for creating, upgrading, scaling, and deleting clusters - what Gardener calls "Shoot" clusters.

In CobaltCore, Gardener provisions the Kubernetes clusters that the hypervisor operators, OpenStack services, and storage components run on.

Key concepts

• Garden cluster - the control plane where Gardener itself runs and where you create Shoot resources
• Shoot cluster - a Kubernetes cluster managed by Gardener; this is where CobaltCore workloads run
• Machine Controller Manager (MCM) - manages the underlying nodes (machines) of a Shoot cluster

Common operations

Restart a reconciliation

If a Shoot is stuck or needs to re-apply its desired state, trigger a retry:

kubectl annotate shoot <shoot-name> -n <project-namespace> gardener.cloud/operation=retry

Reprovision a node

To force a node to be deleted and reprovisioned by the Machine Controller Manager:

kubectl annotate node <node-name> node.machine.sapcloud.io/trigger-deletion-by-mcm=true

MCM will drain the node, delete it, and provision a replacement. See the MCM FAQ for additional node deletion options.

Trigger other Shoot operations

Gardener supports several operations via the gardener.cloud/operation annotation:

Value	Effect
retry	Retry a failed or stuck reconciliation
reconcile	Force a full reconciliation
rotate-credentials-complete	Complete a credentials rotation

See the Gardener Shoot operations docs for the full list.