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You can create a different machine set to serve a specific purpose in your OpenShift Container Platform cluster on VMware vSphere. For example, you might create infrastructure machine sets and related machines so that you can move supporting workloads to the new machines.

This process is not applicable for clusters with manually provisioned machines. You can use the advanced machine management and scaling capabilities only in clusters where the Machine API is operational.

Machine API overview

The Machine API is a combination of primary resources that are based on the upstream Cluster API project and custom OpenShift Container Platform resources.

For OpenShift Container Platform 4.9 clusters, the Machine API performs all node host provisioning management actions after the cluster installation finishes. Because of this system, OpenShift Container Platform 4.9 offers an elastic, dynamic provisioning method on top of public or private cloud infrastructure.

The two primary resources are:

Machines

A fundamental unit that describes the host for a node. A machine has a providerSpec specification, which describes the types of compute nodes that are offered for different cloud platforms. For example, a machine type for a worker node on Amazon Web Services (AWS) might define a specific machine type and required metadata.

Machine sets

MachineSet resources are groups of machines. Machine sets are to machines as replica sets are to pods. If you need more machines or must scale them down, you change the replicas field on the machine set to meet your compute need.

Control plane machines cannot be managed by machine sets.

The following custom resources add more capabilities to your cluster:

Machine autoscaler

The MachineAutoscaler resource automatically scales machines in a cloud. You can set the minimum and maximum scaling boundaries for nodes in a specified machine set, and the machine autoscaler maintains that range of nodes. The MachineAutoscaler object takes effect after a ClusterAutoscaler object exists. Both ClusterAutoscaler and MachineAutoscaler resources are made available by the ClusterAutoscalerOperator object.

Cluster autoscaler

This resource is based on the upstream cluster autoscaler project. In the OpenShift Container Platform implementation, it is integrated with the Machine API by extending the machine set API. You can set cluster-wide scaling limits for resources such as cores, nodes, memory, GPU, and so on. You can set the priority so that the cluster prioritizes pods so that new nodes are not brought online for less important pods. You can also set the scaling policy so that you can scale up nodes but not scale them down.

Machine health check

The MachineHealthCheck resource detects when a machine is unhealthy, deletes it, and, on supported platforms, makes a new machine.

In OpenShift Container Platform version 3.11, you could not roll out a multi-zone architecture easily because the cluster did not manage machine provisioning. Beginning with OpenShift Container Platform version 4.1, this process is easier. Each machine set is scoped to a single zone, so the installation program sends out machine sets across availability zones on your behalf. And then because your compute is dynamic, and in the face of a zone failure, you always have a zone for when you must rebalance your machines. The autoscaler provides best-effort balancing over the life of a cluster.

Sample YAML for a machine set custom resource on vSphere

This sample YAML defines a machine set that runs on VMware vSphere and creates nodes that are labeled with node-role.kubernetes.io/<role>: "".

In this sample, <infrastructure_id> is the infrastructure ID label that is based on the cluster ID that you set when you provisioned the cluster, and <role> is the node label to add.

apiVersion: machine.openshift.io/v1beta1
kind: MachineSet
metadata:
  creationTimestamp: null
  labels:
    machine.openshift.io/cluster-api-cluster: <infrastructure_id> (1)
  name: <infrastructure_id>-<role> (2)
  namespace: openshift-machine-api
spec:
  replicas: 1
  selector:
    matchLabels:
      machine.openshift.io/cluster-api-cluster: <infrastructure_id> (1)
      machine.openshift.io/cluster-api-machineset: <infrastructure_id>-<role> (2)
  template:
    metadata:
      creationTimestamp: null
      labels:
        machine.openshift.io/cluster-api-cluster: <infrastructure_id> (1)
        machine.openshift.io/cluster-api-machine-role: <role> (3)
        machine.openshift.io/cluster-api-machine-type: <role> (3)
        machine.openshift.io/cluster-api-machineset: <infrastructure_id>-<role> (2)
    spec:
      metadata:
        creationTimestamp: null
        labels:
          node-role.kubernetes.io/<role>: "" (3)
      providerSpec:
        value:
          apiVersion: vsphereprovider.openshift.io/v1beta1
          credentialsSecret:
            name: vsphere-cloud-credentials
          diskGiB: 120
          kind: VSphereMachineProviderSpec
          memoryMiB: 8192
          metadata:
            creationTimestamp: null
          network:
            devices:
            - networkName: "<vm_network_name>" (4)
          numCPUs: 4
          numCoresPerSocket: 1
          snapshot: ""
          template: <vm_template_name> (5)
          userDataSecret:
            name: worker-user-data
          workspace:
            datacenter: <vcenter_datacenter_name> (6)
            datastore: <vcenter_datastore_name> (7)
            folder: <vcenter_vm_folder_path> (8)
            resourcepool: <vsphere_resource_pool> (9)
            server: <vcenter_server_ip> (10)
1 Specify the infrastructure ID that is based on the cluster ID that you set when you provisioned the cluster. If you have the OpenShift CLI (oc) installed, you can obtain the infrastructure ID by running the following command:
$ oc get -o jsonpath='{.status.infrastructureName}{"\n"}' infrastructure cluster
2 Specify the infrastructure ID and node label.
3 Specify the node label to add.
4 Specify the vSphere VM network to deploy the machine set to. This VM network must be where other compute machines reside in the cluster.
5 Specify the vSphere VM clone of the template to use, such as user-5ddjd-rhcos.

Do not specify the original VM template. The VM template must remain off and must be cloned for new RHCOS machines. Starting the VM template configures the VM template as a VM on the platform, which prevents it from being used as a template that machine sets can apply configurations to.

6 Specify the vCenter Datacenter to deploy the machine set on.
7 Specify the vCenter Datastore to deploy the machine set on.
8 Specify the path to the vSphere VM folder in vCenter, such as /dc1/vm/user-inst-5ddjd.
9 Specify the vSphere resource pool for your VMs.
10 Specify the vCenter server IP or fully qualified domain name.

Minimum required vCenter privileges for machine set management

To manage machine sets in an OpenShift Container Platform cluster on vCenter, you must use an account with privileges to read, create, and delete the required resources. Using an account that has global administrative privileges is the simplest way to access all of the necessary permissions.

If you cannot use an account with global administrative privileges, you must create roles to grant the minimum required privileges. The following table lists the minimum vCenter roles and privileges that are required to create, scale, and delete machine sets and to delete machines in your OpenShift Container Platform cluster.

Minimum vCenter roles and privileges required for machine set management
vSphere object for role When required Required privileges

vSphere vCenter

Always

InventoryService.Tagging.AttachTag
InventoryService.Tagging.CreateCategory
InventoryService.Tagging.CreateTag
InventoryService.Tagging.DeleteCategory
InventoryService.Tagging.DeleteTag
InventoryService.Tagging.EditCategory
InventoryService.Tagging.EditTag
Sessions.ValidateSession
StorageProfile.Update1
StorageProfile.View1

vSphere vCenter Cluster

Always

Resource.AssignVMToPool

vSphere Datastore

Always

Datastore.AllocateSpace
Datastore.Browse

vSphere Port Group

Always

Network.Assign

Virtual Machine Folder

Always

VirtualMachine.Config.AddRemoveDevice
VirtualMachine.Config.AdvancedConfig
VirtualMachine.Config.Annotation
VirtualMachine.Config.CPUCount
VirtualMachine.Config.DiskExtend
VirtualMachine.Config.Memory
VirtualMachine.Config.Settings
VirtualMachine.Interact.PowerOff
VirtualMachine.Interact.PowerOn
VirtualMachine.Inventory.CreateFromExisting
VirtualMachine.Inventory.Delete
VirtualMachine.Provisioning.Clone

vSphere vCenter Datacenter

If the installation program creates the virtual machine folder

Resource.AssignVMToPool
VirtualMachine.Provisioning.DeployTemplate

1 The StorageProfile.Update and StorageProfile.View permissions are required only for storage backends that use the Container Storage Interface (CSI).

Some CSI drivers and features are in Technology Preview in OpenShift Container Platform 4.9. For more information, see CSI drivers supported by OpenShift Container Platform.

The following table details the permissions and propagation settings that are required for machine set management.

Required permissions and propagation settings
vSphere object Folder type Propagate to children Permissions required

vSphere vCenter

Always

Not required

Listed required privileges

vSphere vCenter Datacenter

Existing folder

Not required

ReadOnly permission

Installation program creates the folder

Required

Listed required privileges

vSphere vCenter Cluster

Always

Required

Listed required privileges

vSphere vCenter Datastore

Always

Not required

Listed required privileges

vSphere Switch

Always

Not required

ReadOnly permission

vSphere Port Group

Always

Not required

Listed required privileges

vSphere vCenter Virtual Machine Folder

Existing folder

Required

Listed required privileges

For more information about creating an account with only the required privileges, see vSphere Permissions and User Management Tasks in the vSphere documentation.

Additional resources

Creating a machine set

In addition to the ones created by the installation program, you can create your own machine sets to dynamically manage the machine compute resources for specific workloads of your choice.

Prerequisites
  • Deploy an OpenShift Container Platform cluster.

  • Install the OpenShift CLI (oc).

  • Log in to oc as a user with cluster-admin permission.

  • Create a tag inside your vCenter instance based on the cluster API name. This tag is utilized by the machine set to associate the OpenShift Container Platform nodes to the provisioned virtual machines (VM). For directions on creating tags in vCenter, see the VMware documentation for vSphere Tags and Attributes.

  • Have the necessary permissions to deploy VMs in your vCenter instance and have the required access to the datastore specified.

Procedure
  1. Create a new YAML file that contains the machine set custom resource (CR) sample and is named <file_name>.yaml.

    Ensure that you set the <clusterID> and <role> parameter values.

    1. If you are not sure which value to set for a specific field, you can check an existing machine set from your cluster:

      $ oc get machinesets -n openshift-machine-api
      Example output
      NAME                                DESIRED   CURRENT   READY   AVAILABLE   AGE
      agl030519-vplxk-worker-us-east-1a   1         1         1       1           55m
      agl030519-vplxk-worker-us-east-1b   1         1         1       1           55m
      agl030519-vplxk-worker-us-east-1c   1         1         1       1           55m
      agl030519-vplxk-worker-us-east-1d   0         0                             55m
      agl030519-vplxk-worker-us-east-1e   0         0                             55m
      agl030519-vplxk-worker-us-east-1f   0         0                             55m
    2. Check values of a specific machine set:

      $ oc get machineset <machineset_name> -n \
           openshift-machine-api -o yaml
      Example output
      ...
      template:
          metadata:
            labels:
              machine.openshift.io/cluster-api-cluster: agl030519-vplxk (1)
              machine.openshift.io/cluster-api-machine-role: worker (2)
              machine.openshift.io/cluster-api-machine-type: worker
              machine.openshift.io/cluster-api-machineset: agl030519-vplxk-worker-us-east-1a
      1 The cluster ID.
      2 A default node label.
  2. Create the new MachineSet CR:

    $ oc create -f <file_name>.yaml
  3. View the list of machine sets:

    $ oc get machineset -n openshift-machine-api
    Example output
    NAME                                DESIRED   CURRENT   READY   AVAILABLE   AGE
    agl030519-vplxk-infra-us-east-1a    1         1         1       1           11m
    agl030519-vplxk-worker-us-east-1a   1         1         1       1           55m
    agl030519-vplxk-worker-us-east-1b   1         1         1       1           55m
    agl030519-vplxk-worker-us-east-1c   1         1         1       1           55m
    agl030519-vplxk-worker-us-east-1d   0         0                             55m
    agl030519-vplxk-worker-us-east-1e   0         0                             55m
    agl030519-vplxk-worker-us-east-1f   0         0                             55m

    When the new machine set is available, the DESIRED and CURRENT values match. If the machine set is not available, wait a few minutes and run the command again.