Managing hosted control planes

After you configure your environment for hosted control planes and create a hosted cluster, you can further manage your clusters and nodes.

Updates for hosted control planes

Updates for hosted control planes involve updating the hosted cluster and the node pools. For a cluster to remain fully operational during an update process, you must meet the requirements of the Kubernetes version skew policy while completing the control plane and node updates.

Updates for the hosted cluster

The spec.release value dictates the version of the control plane. The HostedCluster object transmits the intended spec.release value to the HostedControlPlane.spec.release value and runs the appropriate Control Plane Operator version.

The hosted control plane manages the rollout of the new version of the control plane components along with any OKD components through the new version of the Cluster Version Operator (CVO).

Updates for node pools

With node pools, you can configure the software that is running in the nodes by exposing the spec.release and spec.config values. You can start a rolling node pool update in the following ways:

  • Changing the spec.release or spec.config values.

  • Changing any platform-specific field, such as the AWS instance type. The result is a set of new instances with the new type.

  • Changing the cluster configuration, if the change propagates to the node.

Node pools support replace updates and in-place updates. The nodepool.spec.release value dictates the version of any particular node pool. A NodePool object completes a replace or an in-place rolling update according to the .spec.management.upgradeType value.

After you create a node pool, you cannot change the update type. If you want to change the update type, you must create a node pool and delete the other one.

Replace updates for node pools

A replace update creates instances in the new version while it removes old instances from the previous version. This update type is effective in cloud environments where this level of immutability is cost effective.

Replace updates do not preserve any manual changes because the node is entirely re-provisioned.

In place updates for node pools

An in-place update directly updates the operating systems of the instances. This type is suitable for environments where the infrastructure constraints are higher, such as bare metal.

In-place updates can preserve manual changes, but will report errors if you make manual changes to any file system or operating system configuration that the cluster directly manages, such as kubelet certificates.

Updating node pools for hosted control planes

On hosted control planes, you update your version of OKD by updating the node pools. The node pool version must not surpass the hosted control plane version.

Procedure

  • To start the process to update to a new version of OKD, change the spec.release.image value of the node pool by entering the following command:

    1. $ oc -n NAMESPACE patch HC HCNAME --patch '{"spec":{"release":{"image": "example"}}}' --type=merge

Verification

  • To verify that the new version was rolled out, check the .status.version value and the status conditions.

Configuring node pools for hosted control planes

On hosted control planes, you can configure node pools by creating a MachineConfig object inside of a config map in the management cluster.

Procedure

  1. To create a MachineConfig object inside of a config map in the management cluster, enter the following information:

    1. apiVersion: v1
    2. kind: ConfigMap
    3. metadata:
    4.   name: <configmap-name>
    5.   namespace: clusters
    6. data:
    7.   config: |
    8.     apiVersion: machineconfiguration.openshift.io/v1
    9.     kind: MachineConfig
    10.     metadata:
    11.       labels:
    12.         machineconfiguration.openshift.io/role: worker
    13.       name: <machineconfig-name>
    14.     spec:
    15.       config:
    16.         ignition:
    17.           version: 3.2.0
    18.         storage:
    19.           files:
    20.           - contents:
    21.               source: data:...
    22.             mode: 420
    23.             overwrite: true
    24.             path: ${PATH} (1)
    1Sets the path on the node where the MachineConfig object is stored.

  2. After you add the object to the config map, you can apply the config map to the node pool as follows:

    1. spec:
    2.   config:
    3.     - name: ${CONFIGMAP_NAME}

Configuring node tuning in a hosted cluster

Hosted control planes is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

To set node-level tuning on the nodes in your hosted cluster, you can use the Node Tuning Operator. In hosted control planes, you can configure node tuning by creating config maps that contain Tuned objects and referencing those config maps in your node pools.

Procedure

  1. Create a config map that contains a valid tuned manifest, and reference the manifest in a node pool. In the following example, a Tuned manifest defines a profile that sets vm.dirty_ratio to 55 on nodes that contain the tuned-1-node-label node label with any value. Save the following ConfigMap manifest in a file named tuned-1.yaml:

    1.     apiVersion: v1
    2.     kind: ConfigMap
    3.     metadata:
    4.       name: tuned-1
    5.       namespace: clusters
    6.     data:
    7.       tuning: |
    8.         apiVersion: tuned.openshift.io/v1
    9.         kind: Tuned
    10.         metadata:
    11.           name: tuned-1
    12.           namespace: openshift-cluster-node-tuning-operator
    13.         spec:
    14.           profile:
    15.           - data: |
    16.               [main]
    17.               summary=Custom OpenShift profile
    18.               include=openshift-node
    19.               [sysctl]
    20.               vm.dirty_ratio="55"
    21.             name: tuned-1-profile
    22.           recommend:
    23.           - priority: 20
    24.             profile: tuned-1-profile

    If you do not add any labels to an entry in the spec.recommend section of the Tuned spec, node-pool-based matching is assumed, so the highest priority profile in the spec.recommend section is applied to nodes in the pool. Although you can achieve more fine-grained node-label-based matching by setting a label value in the Tuned .spec.recommend.match section, node labels will not persist during an upgrade unless you set the .spec.management.upgradeType value of the node pool to InPlace.

  2. Create the ConfigMap object in the management cluster:

    1. $ oc --kubeconfig="$MGMT_KUBECONFIG" create -f tuned-1.yaml

  3. Reference the ConfigMap object in the spec.tuningConfig field of the node pool, either by editing a node pool or creating one. In this example, assume that you have only one NodePool, named nodepool-1, which contains 2 nodes.

    1.     apiVersion: hypershift.openshift.io/v1alpha1
    2.     kind: NodePool
    3.     metadata:
    4.       ...
    5.       name: nodepool-1
    6.       namespace: clusters
    7.     ...
    8.     spec:
    9.       ...
    10.       tuningConfig:
    11.       - name: tuned-1
    12.     status:
    13.     ...

    You can reference the same config map in multiple node pools. In hosted control planes, the Node Tuning Operator appends a hash of the node pool name and namespace to the name of the Tuned CRs to distinguish them. Outside of this case, do not create multiple TuneD profiles of the same name in different Tuned CRs for the same hosted cluster.

Verification

Now that you have created the ConfigMap object that contains a Tuned manifest and referenced it in a NodePool, the Node Tuning Operator syncs the Tuned objects into the hosted cluster. You can verify which Tuned objects are defined and which TuneD profiles are applied to each node.

  1. List the Tuned objects in the hosted cluster:

    1. $ oc --kubeconfig="$HC_KUBECONFIG" get Tuneds -n openshift-cluster-node-tuning-operator

    Example output

    1. NAME       AGE
    2. default    7m36s
    3. rendered   7m36s
    4. tuned-1    65s

  2. List the Profile objects in the hosted cluster:

    1. $ oc --kubeconfig="$HC_KUBECONFIG" get Profiles -n openshift-cluster-node-tuning-operator

    Example output

    1. NAME                           TUNED            APPLIED   DEGRADED   AGE
    2. nodepool-1-worker-1            tuned-1-profile  True      False      7m43s
    3. nodepool-1-worker-2            tuned-1-profile  True      False      7m14s

    If no custom profiles are created, the openshift-node profile is applied by default.

  3. To confirm that the tuning was applied correctly, start a debug shell on a node and check the sysctl values:

    1. $ oc --kubeconfig="$HC_KUBECONFIG" debug node/nodepool-1-worker-1 -- chroot /host sysctl vm.dirty_ratio

    Example output

    1. vm.dirty_ratio = 55

Deleting a hosted cluster

The steps to delete a hosted cluster differ depending on which provider you use.

Procedure

Next steps

If you want to disable the hosted control plane feature, see Disabling the hosted control plane feature.