NodePool lifecycle

NodePools represent homogeneous groups of Nodes with a common lifecycle management and upgrade cadence.

Upgrades and data propagation

NodePools support two types of rolling upgrades: Replace and InPlace, specified via UpgradeType.

For a comprehensive reference on what triggers a rollout, upgrade strategies, rollout lifecycle, and monitoring, see NodePool Rollouts.

Triggering Upgrades examples

Upgrading to a new OCP version

These upgrades can be triggered via changing the spec.release.image of the NodePool. Note that you should only upgrade NodePools to the current version of the Hosted Control Plane.

Adding a new MachineConfig

You can create a MachineConfig inside a ConfigMap in the management cluster as follows:

apiVersion: v1
kind: ConfigMap
metadata:
  name: ${CONFIGMAP_NAME}
  namespace: clusters
data:
  config: |
    apiVersion: machineconfiguration.openshift.io/v1
    kind: MachineConfig
    metadata:
      labels:
        machineconfiguration.openshift.io/role: worker
      name: ${MACHINECONFIG_NAME}
    spec:
      config:
        ignition:
          version: 3.2.0
        storage:
          files:
          - contents:
              source: data:...
            mode: 420
            overwrite: true
            path: ${PATH}

Once that is applied to the cluster, you can specify that to the NodePool via:

spec:
  config:
    - name: ${CONFIGMAP_NAME}

Scale Down

Scaling a NodePool down will remove Nodes from the hosted cluster.

Scaling To Zero

Node(s) can become stuck when removing all Nodes from a cluster (scaling NodePool(s) down to zero) because the Node(s) cannot be drained successfully from the cluster.

Several conditions can prevent Node(s) from being drained successfully:

• The hosted cluster contains PodDisruptionBudgets that require at least
• The hosted cluster contains pods that use `PersistentVolumes``

Prevention

To prevent Nodes from becoming stuck when scaling down, set the .spec.nodeDrainTimeout and .spec.nodeVolumeDetachTimeout in the NodePool CR to a value greater than 0s.

This forces Nodes to be removed once the timeout specified in the field has been reached, regardless of whether the node can be drained or the volumes can be detached successfully.