第 1 章 Creating machine sets

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 4.5 clusters, the Machine API performs all node host provisioning management actions after the cluster installation finishes. Because of this system, OpenShift Container Platform 4.5 offers an elastic, dynamic provisioning method on top of public or private cloud infrastructure.

The two primary resources are:

The following custom resources add more capabilities to your cluster:

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.

This sample YAML defines a machine set that runs in the us-east-1a Amazon Web Services (AWS) zone and creates nodes that are labeled with node-role.kubernetes.io/<role>: ""

In this sample, <infrastructureID> 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: <infrastructureID> 1
  name: <infrastructureID>-<role>-<zone> 2
  namespace: openshift-machine-api
spec:
  replicas: 1
  selector:
    matchLabels:
      machine.openshift.io/cluster-api-cluster: <infrastructureID> 3
      machine.openshift.io/cluster-api-machineset: <infrastructureID>-<role>-<zone> 4
  template:
    metadata:
      labels:
        machine.openshift.io/cluster-api-cluster: <infrastructureID> 5
        machine.openshift.io/cluster-api-machine-role: <role> 6
        machine.openshift.io/cluster-api-machine-type: <role> 7
        machine.openshift.io/cluster-api-machineset: <infrastructureID>-<role>-<zone> 8
    spec:
      metadata:
        labels:
          node-role.kubernetes.io/<role>: "" 9
      providerSpec:
        value:
          ami:
            id: ami-046fe691f52a953f9 10
          apiVersion: awsproviderconfig.openshift.io/v1beta1
          blockDevices:
            - ebs:
                iops: 0
                volumeSize: 120
                volumeType: gp2
          credentialsSecret:
            name: aws-cloud-credentials
          deviceIndex: 0
          iamInstanceProfile:
            id: <infrastructureID>-worker-profile 11
          instanceType: m4.large
          kind: AWSMachineProviderConfig
          placement:
            availabilityZone: us-east-1a
            region: us-east-1
          securityGroups:
            - filters:
                - name: tag:Name
                  values:
                    - <infrastructureID>-worker-sg 12
          subnet:
            filters:
              - name: tag:Name
                values:
                  - <infrastructureID>-private-us-east-1a 13
          tags:
            - name: kubernetes.io/cluster/<infrastructureID> 14
              value: owned
          userDataSecret:
            name: worker-user-data

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.

You can save on costs by creating a machine set running on AWS that deploys machines as non-guaranteed Spot Instances. Spot Instances use available AWS EC2 capacity and are less expensive than On-Demand Instances. You can use Spot Instances for workloads that can tolerate interruptions, such as batch or stateless, horizontally scalable workloads.

AWS EC2 can terminate a Spot Instance at any time. AWS gives a two-minute warning to the user when an interruption occurs. OpenShift Container Platform begins to remove the workloads from the affected instances when AWS issues the termination warning.

Interruptions can occur when using Spot Instances for the following reasons:

When AWS terminates an instance, a termination handler running on the Spot Instance node deletes the machine resource. To satisfy the machine set replicas quantity, the machine set creates a machine that requests a Spot Instance.

You can launch a Spot Instance on AWS by adding spotMarketOptions to your machine set YAML file.

Optional: You can set the spotMarketOptions.maxPrice field to limit the cost of the Spot Instance. For example, you can set maxPrice: '2.50'.

If the maxPrice is set, this value is used as the hourly maximum spot price. If it is not set, the maximum price defaults to charge up to the On-Demand Instance price.