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You can create a different machine set to serve a specific purpose in your OKD cluster on Alibaba Cloud. 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 OKD resources.

For OKD 4.10 clusters, the Machine API performs all node host provisioning management actions after the cluster installation finishes. Because of this system, OKD 4.10 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 OKD 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 OKD version 3.11, you could not roll out a multi-zone architecture easily because the cluster did not manage machine provisioning. Beginning with OKD 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. In global Azure regions that do not have multiple availability zones, you can use availability sets to ensure high availability. The autoscaler provides best-effort balancing over the life of a cluster.

Sample YAML for a machine set custom resource on Alibaba Cloud

This sample YAML defines a machine set that runs in a specified Alibaba Cloud zone in a region 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:
  labels:
    machine.openshift.io/cluster-api-cluster: <infrastructure_id> (1)
    machine.openshift.io/cluster-api-machine-role: <role> (2)
    machine.openshift.io/cluster-api-machine-type: <role> (2)
  name: <infrastructure_id>-<role>-<zone> (3)
  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>-<zone> (3)
  template:
    metadata:
      labels:
        machine.openshift.io/cluster-api-cluster: <infrastructure_id> (1)
        machine.openshift.io/cluster-api-machine-role: <role> (2)
        machine.openshift.io/cluster-api-machine-type: <role> (2)
        machine.openshift.io/cluster-api-machineset: <infrastructure_id>-<role>-<zone> (3)
    spec:
      metadata:
        labels:
          node-role.kubernetes.io/<role>: ""
      providerSpec:
        value:
          apiVersion: machine.openshift.io/v1
          credentialsSecret:
            name: alibabacloud-credentials
          imageId: <image_id> (4)
          instanceType: <instance_type> (5)
          kind: AlibabaCloudMachineProviderConfig
          ramRoleName: <infrastructure_id>-role-worker (6)
          regionId: <region> (7)
          resourceGroup: (8)
            id: <resource_group_id>
            type: ID
          securityGroups:
          - tags: (9)
            - Key: Name
              Value: <infrastructure_id>-sg-<role>
            type: Tags
          systemDisk: (10)
            category: cloud_essd
            size: <disk_size>
          tag: (9)
          - Key: kubernetes.io/cluster/<infrastructure_id>
            Value: owned
          userDataSecret:
            name: <user_data_secret> (11)
          vSwitch:
            tags: (9)
            - Key: Name
              Value: <infrastructure_id>-vswitch-<zone>
            type: Tags
          vpcId: ""
          zoneId: <zone> (12)
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 node label to add.
3 Specify the infrastructure ID, node label, and zone.
4 Specify the image to use. Use an image from an existing default machine set for the cluster.
5 Specify the instance type you want to use for the machine set.
6 Specify the name of the RAM role to use for the machine set. Use the value that the installer populates in the default machine set.
7 Specify the region to place machines on.
8 Specify the resource group and type for the cluster. You can use the value that the installer populates in the default machine set, or specify a different one.
9 Specify the tags to use for the machine set. Minimally, you must include the tags shown in this example, with appropriate values for your cluster. You can include additional tags, including the tags that the installer populates in the default machine set it creates, as needed.
10 Specify the type and size of the root disk. Use the category value that the installer populates in the default machine set it creates. If required, specify a different value in gigabytes for size.
11 Specify the name of the secret in the user data YAML file that is in the openshift-machine-api namespace. Use the value that the installer populates in the default machine set.
12 Specify the zone within your region to place machines on. Be sure that your region supports the zone that you specify.

Machine set parameters for Alibaba Cloud usage statistics

The default machine sets that the installer creates for Alibaba Cloud clusters include nonessential tag values that Alibaba Cloud uses internally to track usage statistics. These tags are populated in the securityGroups, tag, and vSwitch parameters of the spec.template.spec.providerSpec.value list.

When creating machine sets to deploy additional machines, you must include the required Kubernetes tags. The usage statistics tags are applied by default, even if they are not specified in the machine sets you create. You can also include additional tags as needed.

The following YAML snippets indicate which tags in the default machine sets are optional and which are required.

Tags in spec.template.spec.providerSpec.value.securityGroups
spec:
  template:
    spec:
      providerSpec:
        value:
          securityGroups:
          - tags:
            - Key: kubernetes.io/cluster/<infrastructure_id> (1)
              Value: owned
            - Key: GISV
              Value: ocp
            - Key: sigs.k8s.io/cloud-provider-alibaba/origin (1)
              Value: ocp
            - Key: Name
              Value: <infrastructure_id>-sg-<role> (2)
            type: Tags
1 Optional: This tag is applied even when not specified in the machine set.
2 Required.

where:

  • <infrastructure_id> is the infrastructure ID that is based on the cluster ID that you set when you provisioned the cluster.

  • <role> is the node label to add.

Tags in spec.template.spec.providerSpec.value.tag
spec:
  template:
    spec:
      providerSpec:
        value:
          tag:
          - Key: kubernetes.io/cluster/<infrastructure_id> (2)
            Value: owned
          - Key: GISV (1)
            Value: ocp
          - Key: sigs.k8s.io/cloud-provider-alibaba/origin (1)
            Value: ocp
1 Optional: This tag is applied even when not specified in the machine set.
2 Required.

where <infrastructure_id> is the infrastructure ID that is based on the cluster ID that you set when you provisioned the cluster.

Tags in spec.template.spec.providerSpec.value.vSwitch
spec:
  template:
    spec:
      providerSpec:
        value:
          vSwitch:
            tags:
            - Key: kubernetes.io/cluster/<infrastructure_id> (1)
              Value: owned
            - Key: GISV (1)
              Value: ocp
            - Key: sigs.k8s.io/cloud-provider-alibaba/origin (1)
              Value: ocp
            - Key: Name
              Value: <infrastructure_id>-vswitch-<zone> (2)
            type: Tags
1 Optional: This tag is applied even when not specified in the machine set.
2 Required.

where:

  • <infrastructure_id> is the infrastructure ID that is based on the cluster ID that you set when you provisioned the cluster.

  • <zone> is the zone within your region to place machines on.

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 OKD cluster.

  • Install the OpenShift CLI (oc).

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

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.