Windows Container Support for OpenShift

OpenShift Container Platform 4.6

Windows Container Support for OpenShift Guide

Red Hat OpenShift Documentation Team

Abstract

Windows Container Support for OpenShift guide provides built-in support for running Microsoft Windows Server containers on OpenShift Container Platform. This guide provides all the details.

Chapter 1. Windows Container Support for Red Hat OpenShift release notes

1.1. About Windows Container Support for Red Hat OpenShift

Windows Container Support for Red Hat OpenShift is a feature providing the ability to run Windows compute nodes in an OpenShift Container Platform cluster. This is possible by using the Red Hat Windows Machine Config Operator (WMCO) to install and manage Windows nodes. With Windows nodes available, you can run Windows container workloads in OpenShift Container Platform.

The release notes for Red Hat OpenShift for Windows Containers tracks the development of the WMCO, which provides all Windows container workload capabilities in OpenShift Container Platform.

1.2. Getting support

You must have a subscription to receive support for the Red Hat WMCO. Deploying Windows container workloads in production clusters is not supported without a subscription. If you do not have a subscription, you can use the community WMCO, a distribution that lacks official support. Request support through the Red Hat Customer Portal.

1.3. Release notes for Red Hat Windows Machine Config Operator 1.0.3

The WMCO 1.0.3 is now available with bug fixes and security updates. The components of the WMCO were released in RHBA-2021:0410.

The support statements and known issues documented for the WMCO 1.0.2 release also apply for this release of the WMCO.

1.4. Release notes for Red Hat Windows Machine Config Operator 1.0.2

This release of the WMCO provides initial support for running Windows compute nodes in an OpenShift Container Platform cluster. The components of the WMCO were released in RHBA-2020:5596.

WMCO supports self-managed clusters built using installer-provisioned infrastructure running on the following cloud providers:

  • Amazon Web Services (AWS)
  • Microsoft Azure

The following Windows Server operating systems are supported in the initial release of the WMCO:

  • Windows Server Long-Term Servicing Channel (LTSC): Windows Server 2019

1.4.1. Known issues

  • If you have a cluster with two Windows nodes, and you create a web server deployment with two replicas, the pods each land on a Windows compute node. In this scenario, if you create a Service object with type LoadBalancer, communication with the load balancer endpoint is flaky. To mitigate this issue, you must use Windows Server 2019 with a version 10.0.17763.1457 or earlier. (BZ#1905950)

    To pick the correct image for the MachineSet object, follow the instructions based on your cloud provider:

    AWS

    1. Run the following command to list AWS image info:

      $ aws ec2 describe-images \
          --filters Name=name,Values=Windows_Server-2019-English-Full-ContainersLatest-2020.09.09
          --region <region> \1
          --query 'Images[*].[ImageId]' \
          --output=json | jq .[0][0]
      1
      Specify the region your cluster is using.
    2. Find the AMI ID for a supported Windows image.

    Azure

    1. Run the following command to list Azure image info:

      $ az vm image list --all --location <location> \1
          --publisher MicrosoftWindowsServer \
          --offer WindowsServer \
          --sku 2019-Datacenter-with-Containers \
          --query "[?contains(version, '17763.1457.2009030514')]"
      1
      Specify the location your cluster is using.
    2. Find a WindowsServer image offering that defines the 2019-Datacenter-with-Containers SKU with version 17763.1457.2009030514 or earlier.

      Example output

          "offer": "WindowsServer",
          "publisher": "MicrosoftWindowsServer",
          "sku": "2019-Datacenter-with-Containers",
          "urn": "MicrosoftWindowsServer:WindowsServer:2019-Datacenter-with-Containers:17763.1457.2009030514",
          "version": "17763.1457.2009030514"

Chapter 2. Understanding Windows container workloads

Windows Container Support for Red Hat OpenShift provides built-in support for running Microsoft Windows Server containers on OpenShift Container Platform. For those that administer heterogeneous environments with a mix of Linux and Windows workloads, OpenShift Container Platform allows you to deploy Windows workloads running on Windows Server containers while also providing traditional Linux workloads hosted on Red Hat Enterprise Linux CoreOS (RHCOS) or Red Hat Enterprise Linux (RHEL).

Windows container workloads are supported for clusters running on the following cloud providers:

  • Amazon Web Services (AWS)
  • Microsoft Azure

The following Windows Server operating systems are supported for OpenShift Container Platform 4.6:

  • Windows Server Long-Term Servicing Channel (LTSC): Windows Server 2019

For more information, see Microsoft’s documentation on Windows Server channels.

Note

Multi-tenancy for clusters that have Windows nodes is not supported. Hostile multi-tenant usage introduces security concerns in all Kubernetes environments. Additional security features like pod security policies, or more fine-grained role-based access control (RBAC) for nodes, make exploits more difficult. However, if you choose to run hostile multi-tenant workloads, a hypervisor is the only security option you should use. The security domain for Kubernetes encompasses the entire cluster, not an individual node. For these types of hostile multi-tenant workloads, you should use physically isolated clusters.

Windows Server Containers provide resource isolation using a shared kernel but are not intended to be used in hostile multitenancy scenarios. Scenarios that involve hostile multitenancy should use Hyper-V Isolated Containers to strongly isolate tenants.

2.1. Windows workload management

To run Windows workloads in your cluster, you must first install the Windows Machine Config Operator (WMCO). The WMCO is a Linux-based Operator that runs on Linux-based control plane and compute nodes. The WMCO orchestrates the process of deploying and managing Windows workloads on a cluster.

Figure 2.1. WMCO design

WMCO workflow

Before deploying Windows workloads, you must create a Windows compute node and have it join the cluster. The Windows node hosts the Windows workloads in a cluster, and can run alongside other Linux-based compute nodes. You can create a Windows compute node by creating a Windows machine set to host Windows Server compute machines. You must apply a Windows-specific label to the machine set that specifies a Windows OS image that has the Docker-formatted container runtime add-on enabled.

Important

Currently, the Docker-formatted container runtime is used in Windows nodes. Kubernetes is deprecating Docker as a container runtime; you can reference the Kubernetes documentation for more information in Docker deprecation. Containerd will be the new supported container runtime for Windows nodes in a future release of Kubernetes.

The WMCO watches for machines with the Windows label. After a Windows machine set is detected and its respective machines are provisioned, the WMCO configures the underlying Windows virtual machine (VM) so that it can join the cluster as a compute node.

Figure 2.2. Mixed Windows and Linux workloads

Mixed Windows and Linux workloads

The WMCO expects a predetermined secret in its namespace containing a private key that is used to interact with the Windows instance. WMCO checks for this secret during boot up time and creates a user data secret which you must reference in the Windows MachineSet object that you created. Then the WMCO populates the user data secret with a public key that corresponds to the private key. With this data in place, the cluster can connect to the Windows VM using an SSH connection.

After the cluster establishes a connection with the Windows VM, you can manage the Windows node using similar practices as you would a Linux-based node.

Note

The OpenShift Container Platform web console does not provide node graphs and workload graphs for Windows nodes. No metrics are available for Windows nodes at this time.

Scheduling Windows workloads to a Windows node can be done with typical pod scheduling practices like taints, tolerations, and node selectors; alternatively, you can differentiate your Windows workloads from Linux workloads and other Windows-versioned workloads by using a RuntimeClass object.

2.2. Windows node services

The following Windows-specific services are installed on each Windows node:

ServiceDescription

kubelet

Registers the Windows node and manages its status.

Container Network Interface (CNI) plug-ins

Exposes networking for Windows nodes.

Windows Machine Config Bootstrapper (WMCB)

Configures the kubelet and CNI plug-ins.

hybrid-overlay

Creates the OpenShift Container Platform Host Network Service (HNS).

kube-proxy

Maintains network rules on nodes allowing outside communication.

Chapter 3. Enabling Windows container workloads

Before adding Windows workloads to your cluster, you must install the Windows Machine Config Operator (WMCO), which is available in the OpenShift Container Platform OperatorHub. The WMCO orchestrates the process of deploying and managing Windows workloads on a cluster.

Prerequisites

  • You have access to an OpenShift Container Platform cluster using an account with cluster-admin permissions.
  • You have installed the OpenShift CLI (oc).
  • You have installed your cluster using installer-provisioned infrastructure. Clusters installed with user-provisioned infrastructure are not supported for Windows container workloads.
  • You have configured hybrid networking with OVN-Kubernetes for your cluster. This must be completed during the installation of your cluster. For more information, see Configuring hybrid networking.
  • You are running an OpenShift Container Platform cluster version 4.6.8 or later.

3.1. Installing the Windows Machine Config Operator

You can install the Windows Machine Config Operator using either the web console or OpenShift CLI (oc).

3.1.1. Installing the Windows Machine Config Operator using the web console

You can use the OpenShift Container Platform web console to install the Windows Machine Config Operator (WMCO).

Procedure

  1. From the Administrator perspective in the OpenShift Container Platform web console, navigate to the Operators → OperatorHub page.
  2. Use the Filter by keyword box to search for Windows Machine Config Operator in the catalog. Click the Windows Machine Config Operator tile.
  3. Review the information about the Operator and click Install.
  4. On the Install Operator page:

    1. Select the 4.6 channel as the Update Channel. The 4.6 channel enables the latest stable release of the WMCO to be installed.
    2. The Installation Mode is preconfigured because the WMCO must be available in a single namespace only.
    3. Choose the Installed Namespace for the WMCO. The default Operator recommended namespace is openshift-windows-machine-config-operator.
    4. Select an Approval Strategy.

      • The Automatic strategy allows Operator Lifecycle Manager (OLM) to automatically update the Operator when a new version is available.
      • The Manual strategy requires a user with appropriate credentials to approve the Operator update.
  1. Click Install. The WMCO is now listed on the Installed Operators page.

    Note

    The WMCO is installed automatically into the namespace you defined, like openshift-windows-machine-config-operator.

  2. Verify that the Status shows Succeeded to confirm successful installation of the WMCO.

3.1.2. Installing the Windows Machine Config Operator using the CLI

You can use the OpenShift CLI (oc) to install the Windows Machine Config Operator (WMCO).

Procedure

  1. Create a namespace for the WMCO.

    1. Create a Namespace object YAML file for the WMCO. For example, wmco-namespace.yaml:

      apiVersion: v1
      kind: Namespace
      metadata:
        name: openshift-windows-machine-config-operator 1
      1
      It is recommended to deploy the WMCO in the openshift-windows-machine-config-operator namespace.
    2. Create the namespace:

      $ oc create -f <file-name>.yaml

      For example:

      $ oc create -f wmco-namespace.yaml
  2. Create the Operator group for the WMCO.

    1. Create an OperatorGroup object YAML file. For example, wmco-og.yaml:

      apiVersion: operators.coreos.com/v1
      kind: OperatorGroup
      metadata:
        name: windows-machine-config-operator
        namespace: openshift-windows-machine-config-operator
      spec:
        targetNamespaces:
        - openshift-windows-machine-config-operator
    2. Create the Operator group:

      $ oc create -f <file-name>.yaml

      For example:

      $ oc create -f wmco-og.yaml
  3. Subscribe the namespace to the WMCO.

    1. Create a Subscription object YAML file. For example, wmco-sub.yaml:

      apiVersion: operators.coreos.com/v1alpha1
      kind: Subscription
      metadata:
        name: windows-machine-config-operator
        namespace: openshift-windows-machine-config-operator
      spec:
        channel: "stable" 1
        installPlanApproval: "Automatic" 2
        name: "windows-machine-config-operator"
        source: "redhat-operators" 3
        sourceNamespace: "openshift-marketplace" 4
      1
      Specify stable as the channel.
      2
      Set an approval strategy. You can set Automatic or Manual.
      3
      Specify the redhat-operators catalog source, which contains the windows-machine-config-operator package manifests. If your OpenShift Container Platform is installed on a restricted network, also known as a disconnected cluster, specify the name of the CatalogSource object you created when you configured the Operator LifeCycle Manager (OLM).
      4
      Namespace of the catalog source. Use openshift-marketplace for the default OperatorHub catalog sources.
    2. Create the subscription:

      $ oc create -f <file-name>.yaml

      For example:

      $ oc create -f wmco-sub.yaml

      The WMCO is now installed to the openshift-windows-machine-config-operator.

  4. Verify the WMCO installation:

    $ oc get csv -n openshift-windows-machine-config-operator

    Example output

    NAME                                    DISPLAY                           VERSION   REPLACES   PHASE
    windows-machine-config-operator.1.0.0   Windows Machine Config Operator   1.0.0                Succeeded

3.2. Configuring a secret for the Windows Machine Config Operator

To run the Windows Machine Config Operator (WMCO), you must create a secret in the WMCO namespace containing a private key. This is required to allow the WMCO to communicate with the Windows virtual machine (VM).

Prerequisites

  • You installed the Windows Machine Config Operator (WMCO) using Operator Lifecycle Manager (OLM).
  • You created a PEM-encoded file containing an RSA key.

Procedure

  • Define the secret required to access the Windows VMs:

    $ oc create secret generic cloud-private-key --from-file=private-key.pem=${HOME}/.ssh/<key> \
        -n openshift-windows-machine-config-operator 1
1
You must create the private key in the WMCO namespace, like openshift-windows-machine-config-operator.

It is recommended to use a different private key than the one used when installing the cluster.

Additional Resources

Chapter 4. Creating Windows MachineSet objects

4.1. Creating a Windows MachineSet object on AWS

You can create a Windows MachineSet object to serve a specific purpose in your OpenShift Container Platform cluster on Amazon Web Services (AWS). For example, you might create infrastructure Windows machine sets and related machines so that you can move supporting Windows workloads to the new Windows machines.

Prerequisites

  • You installed the Windows Machine Config Operator (WMCO) using Operator Lifecycle Manager (OLM).
  • You are using a supported Windows Server as the operating system image with the Docker-formatted container runtime add-on enabled.
Important

Currently, the Docker-formatted container runtime is used in Windows nodes. Kubernetes is deprecating Docker as a container runtime; you can reference the Kubernetes documentation for more information in Docker deprecation. Containerd will be the new supported container runtime for Windows nodes in a future release of Kubernetes.

4.1.1. 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 4.6 clusters, the Machine API performs all node host provisioning management actions after the cluster installation finishes. Because of this system, OpenShift Container Platform 4.6 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.

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.

4.1.2. Sample YAML for a Windows MachineSet object on AWS

This sample YAML defines a Windows MachineSet object running on Amazon Web Services (AWS) that the Windows Machine Config Operator (WMCO) can react upon.

apiVersion: machine.openshift.io/v1beta1
kind: MachineSet
metadata:
  labels:
    machine.openshift.io/cluster-api-cluster: <infrastructure_id> 1
  name: <infrastructure_id>-windows-worker-<zone> 2
  namespace: openshift-machine-api
spec:
  replicas: 1
  selector:
    matchLabels:
      machine.openshift.io/cluster-api-cluster: <infrastructure_id> 3
      machine.openshift.io/cluster-api-machineset: <infrastructure_id>-windows-worker-<zone> 4
  template:
    metadata:
      labels:
        machine.openshift.io/cluster-api-cluster: <infrastructure_id> 5
        machine.openshift.io/cluster-api-machine-role: worker
        machine.openshift.io/cluster-api-machine-type: worker
        machine.openshift.io/cluster-api-machineset: <infrastructure_id>-windows-worker-<zone> 6
        machine.openshift.io/os-id: Windows 7
    spec:
      metadata:
        labels:
          node-role.kubernetes.io/worker: "" 8
      providerSpec:
        value:
          ami:
            id: <windows_container_ami> 9
          apiVersion: awsproviderconfig.openshift.io/v1beta1
          blockDevices:
            - ebs:
                iops: 0
                volumeSize: 120
                volumeType: gp2
          credentialsSecret:
            name: aws-cloud-credentials
          deviceIndex: 0
          iamInstanceProfile:
            id: <infrastructure_id>-worker-profile 10
          instanceType: m5a.large
          kind: AWSMachineProviderConfig
          placement:
            availabilityZone: <zone> 11
            region: <region> 12
          securityGroups:
            - filters:
                - name: tag:Name
                  values:
                    - <infrastructure_id>-worker-sg 13
          subnet:
            filters:
              - name: tag:Name
                values:
                  - <infrastructure_id>-private-<zone> 14
          tags:
            - name: kubernetes.io/cluster/<infrastructure_id> 15
              value: owned
          userDataSecret:
            name: windows-user-data 16
            namespace: openshift-machine-api
1 3 5 10 13 14 15
Specify the infrastructure ID that is based on the cluster ID that you set when you provisioned the cluster. You can obtain the infrastructure ID by running the following command:
$ oc get -o jsonpath='{.status.infrastructureName}{"\n"}' infrastructure cluster
2 4 6
Specify the infrastructure ID, worker label, and zone.
7
Configure the machine set as a Windows machine.
8
Configure the Windows node as a compute machine.
9
Specify the AMI ID of a Windows image with a container runtime installed. You must use Windows Server 2019 with a version 10.0.17763.1457 or earlier.
11
Specify the AWS zone, like us-east-1a.
12
Specify the AWS region, like us-east-1.
16
Created by the WMCO when it is configuring the first Windows machine. After that, the windows-user-data is available for all subsequent machine sets to consume.

4.1.3. 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.

Procedure

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

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

    1. If you are not sure about 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-windows-worker-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.

  4. After the new machine set is available, check status of the machine and the node that it references:

    $ oc describe machine <name> -n openshift-machine-api

    For example:

    $ oc describe machine agl030519-vplxk-windows-worker-us-east-1a -n openshift-machine-api

    Example output

    status:
      addresses:
      - address: 10.0.133.18
        type: InternalIP
      - address: ""
        type: ExternalDNS
      - address: ip-10-0-133-18.ec2.internal
        type: InternalDNS
      lastUpdated: "2019-05-03T10:38:17Z"
      nodeRef:
        kind: Node
        name: ip-10-0-133-18.ec2.internal
        uid: 71fb8d75-6d8f-11e9-9ff3-0e3f103c7cd8
      providerStatus:
        apiVersion: awsproviderconfig.openshift.io/v1beta1
        conditions:
        - lastProbeTime: "2019-05-03T10:34:31Z"
          lastTransitionTime: "2019-05-03T10:34:31Z"
          message: machine successfully created
          reason: MachineCreationSucceeded
          status: "True"
          type: MachineCreation
        instanceId: i-09ca0701454124294
        instanceState: running
        kind: AWSMachineProviderStatus

  5. View the new node and confirm that the new node has the label that you specified:

    $ oc get node <node_name> --show-labels

    Review the command output and confirm that node-role.kubernetes.io/<your_label> is in the LABELS list.

Note

Any change to a machine set is not applied to existing machines owned by the machine set. For example, labels edited or added to an existing machine set are not propagated to existing machines and nodes associated with the machine set.

4.1.4. Additional resources

  • For more information on managing machine sets, see the Machine management section.

4.2. Creating a Windows MachineSet object on Azure

You can create a Windows MachineSet object to serve a specific purpose in your OpenShift Container Platform cluster on Microsoft Azure. For example, you might create infrastructure Windows machine sets and related machines so that you can move supporting Windows workloads to the new Windows machines.

Prerequisites

  • You installed the Windows Machine Config Operator (WMCO) using Operator Lifecycle Manager (OLM).
  • You are using a supported Windows Server as the operating system image with the Docker-formatted container runtime add-on enabled.
Important

Currently, the Docker-formatted container runtime is used in Windows nodes. Kubernetes is deprecating Docker as a container runtime; you can reference the Kubernetes documentation for more information in Docker deprecation. Containerd will be the new supported container runtime for Windows nodes in a future release of Kubernetes.

4.2.1. 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 4.6 clusters, the Machine API performs all node host provisioning management actions after the cluster installation finishes. Because of this system, OpenShift Container Platform 4.6 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.

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.

4.2.2. Sample YAML for a Windows MachineSet object on Azure

This sample YAML defines a Windows MachineSet object running on Microsoft Azure that the Windows Machine Config Operator (WMCO) can react upon.

apiVersion: machine.openshift.io/v1beta1
kind: MachineSet
metadata:
  labels:
    machine.openshift.io/cluster-api-cluster: <infrastructure_id> 1
  name: <windows_machine_set_name> 2
  namespace: openshift-machine-api
spec:
  replicas: 1
  selector:
    matchLabels:
      machine.openshift.io/cluster-api-cluster: <infrastructure_id> 3
      machine.openshift.io/cluster-api-machineset: <windows_machine_set_name> 4
  template:
    metadata:
      labels:
        machine.openshift.io/cluster-api-cluster: <infrastructure_id> 5
        machine.openshift.io/cluster-api-machine-role: worker
        machine.openshift.io/cluster-api-machine-type: worker
        machine.openshift.io/cluster-api-machineset: <windows_machine_set_name> 6
        machine.openshift.io/os-id: Windows 7
    spec:
      metadata:
        labels:
          node-role.kubernetes.io/worker: "" 8
      providerSpec:
        value:
          apiVersion: azureproviderconfig.openshift.io/v1beta1
          credentialsSecret:
            name: azure-cloud-credentials
            namespace: openshift-machine-api
          image: 9
            offer: WindowsServer
            publisher: MicrosoftWindowsServer
            resourceID: ""
            sku: 2019-Datacenter-with-Containers
            version: latest
          kind: AzureMachineProviderSpec
          location: <location> 10
          managedIdentity: <infrastructure_id>-identity 11
          networkResourceGroup: <infrastructure_id>-rg 12
          osDisk:
            diskSizeGB: 128
            managedDisk:
              storageAccountType: Premium_LRS
            osType: Windows
          publicIP: false
          resourceGroup: <infrastructure_id>-rg 13
          subnet: <infrastructure_id>-worker-subnet
          userDataSecret:
            name: windows-user-data 14
            namespace: openshift-machine-api
          vmSize: Standard_D2s_v3
          vnet: <infrastructure_id>-vnet 15
          zone: "<zone>" 16
1 3 5 11 12 13 15
Specify the infrastructure ID that is based on the cluster ID that you set when you provisioned the cluster. You can obtain the infrastructure ID by running the following command:
$ oc get -o jsonpath='{.status.infrastructureName}{"\n"}' infrastructure cluster
2 4 6
Specify the Windows machine set name. Windows machine names on Azure cannot be more than 15 characters long. Therefore, the machine set name cannot be more than 9 characters long, due to the way machine names are generated from it.
7
Configure the machine set as a Windows machine.
8
Configure the Windows node as a compute machine.
9
Specify a WindowsServer image offering that defines the 2019-Datacenter-with-Containers SKU with version 17763.1457.2009030514 or earlier.
10
Specify the Azure region, like centralus.
14
Created by the WMCO when it is configuring the first Windows machine. After that, the windows-user-data is available for all subsequent machine sets to consume.
16
Specify the zone within your region to place machines on. Be sure that your region supports the zone that you specify.

4.2.3. 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.

Procedure

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

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

    1. If you are not sure about 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-windows-worker-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.

  4. After the new machine set is available, check status of the machine and the node that it references:

    $ oc describe machine <name> -n openshift-machine-api

    For example:

    $ oc describe machine agl030519-vplxk-windows-worker-us-east-1a -n openshift-machine-api

    Example output

    status:
      addresses:
      - address: 10.0.133.18
        type: InternalIP
      - address: ""
        type: ExternalDNS
      - address: ip-10-0-133-18.ec2.internal
        type: InternalDNS
      lastUpdated: "2019-05-03T10:38:17Z"
      nodeRef:
        kind: Node
        name: ip-10-0-133-18.ec2.internal
        uid: 71fb8d75-6d8f-11e9-9ff3-0e3f103c7cd8
      providerStatus:
        apiVersion: awsproviderconfig.openshift.io/v1beta1
        conditions:
        - lastProbeTime: "2019-05-03T10:34:31Z"
          lastTransitionTime: "2019-05-03T10:34:31Z"
          message: machine successfully created
          reason: MachineCreationSucceeded
          status: "True"
          type: MachineCreation
        instanceId: i-09ca0701454124294
        instanceState: running
        kind: AWSMachineProviderStatus

  5. View the new node and confirm that the new node has the label that you specified:

    $ oc get node <node_name> --show-labels

    Review the command output and confirm that node-role.kubernetes.io/<your_label> is in the LABELS list.

Note

Any change to a machine set is not applied to existing machines owned by the machine set. For example, labels edited or added to an existing machine set are not propagated to existing machines and nodes associated with the machine set.

4.2.4. Additional resources

  • For more information on managing machine sets, see the Machine management section.

Chapter 5. Scheduling Windows container workloads

You can schedule Windows workloads to Windows compute nodes.

Prerequisites

  • You installed the Windows Machine Config Operator (WMCO) using Operator Lifecycle Manager (OLM).
  • You are using a Windows container as the OS image with the Docker-formatted container runtime add-on enabled.
  • You have created a Windows machine set.
Important

Currently, the Docker-formatted container runtime is used in Windows nodes. Kubernetes is deprecating Docker as a container runtime; you can reference the Kubernetes documentation for more information in Docker deprecation. Containerd will be the new supported container runtime for Windows nodes in a future release of Kubernetes.

5.1. Windows pod placement

Before deploying your Windows workloads to the cluster, you must configure your Windows node scheduling so pods are assigned correctly. Since you have a machine hosting your Windows node, it is managed the same as a Linux-based node. Likewise, scheduling a Windows pod to the appropriate Windows node is completed similarly, using mechanisms like taints, tolerations, and node selectors.

With multiple operating systems, and the ability to run multiple Windows OS variants, in the same cluster, you must map your Windows pods to a base Windows OS variant by using a RuntimeClass. For example, if you have multiple Windows nodes running on different Windows Server container versions, the cluster could schedule your Windows pods to an incompatible Windows OS variant. You must have RuntimeClass objects configured for each Windows OS variant on your cluster. Using a RuntimeClass object is also recommended if you have only one Windows OS variant available in your cluster.

For more information, see Microsoft’s documentation on Host and container version compatibility.

Additional resources

5.2. Creating a RuntimeClass object to encapsulate scheduling mechanisms

Using a RuntimeClass object simplifies the use of scheduling mechanisms like taints and tolerations; you deploy a runtime class that encapsulates your taints and tolerations and then apply it to your pods to schedule them to the appropriate node. Creating a runtime class is also necessary in clusters that support multiple operating system variants.

Procedure

  1. Create a RuntimeClass object YAML file. For example, runtime-class.yaml:

    apiVersion: node.k8s.io/v1beta1
    kind: RuntimeClass
    metadata:
      name: <runtime_class_name> 1
    handler: 'docker'
    scheduling:
      nodeSelector: 2
        kubernetes.io/os: 'windows'
        kubernetes.io/arch: 'amd64'
        node.kubernetes.io/windows-build: '10.0.17763'
      tolerations: 3
      - effect: NoSchedule
        key: os
        operator: Equal
        value: "Windows"
    1
    Specify the RuntimeClass object name, which is defined in the pods you want to be managed by this runtime class.
    2
    Specify labels that must be present on nodes that support this runtime class. Pods using this runtime class can only be scheduled to a node matched by this selector. The node selector of the runtime class is merged with the existing node selector of the pod. Any conflicts prevent the pod from being scheduled to the node.
    3
    Specify tolerations to append to pods, excluding duplicates, running with this runtime class during admission. This combines the set of nodes tolerated by the pod and the runtime class.
  2. Create the RuntimeClass object:

    $ oc create -f <file-name>.yaml

    For example:

    $ oc create -f runtime-class.yaml
  3. Apply the RuntimeClass object to your pod to ensure it is scheduled to the appropriate operating system variant:

    apiVersion: v1
    kind: Pod
    metadata:
      name: my-windows-pod
    spec:
      runtimeClassName: <runtime_class_name> 1
    ...
    1
    Specify the runtime class to manage the scheduling of your pod.

5.3. Sample Windows container workload deployment

You can deploy Windows container workloads to your cluster once you have a Windows compute node available.

Note

This sample deployment is provided for reference only.

Example Service object

apiVersion: v1
kind: Service
metadata:
  name: win-webserver
  labels:
    app: win-webserver
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
  selector:
    app: win-webserver
  type: LoadBalancer

Example Deployment object

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: win-webserver
  name: win-webserver
spec:
  selector:
    matchLabels:
      app: win-webserver
  replicas: 1
  template:
    metadata:
      labels:
        app: win-webserver
      name: win-webserver
    spec:
      tolerations:
      - key: "os"
        value: "Windows"
        Effect: "NoSchedule"
      containers:
      - name: windowswebserver
        image: mcr.microsoft.com/windows/servercore:ltsc2019
        imagePullPolicy: IfNotPresent
        command:
        - powershell.exe
        - -command
        - $listener = New-Object System.Net.HttpListener; $listener.Prefixes.Add('http://*:80/'); $listener.Start();Write-Host('Listening at http://*:80/'); while ($listener.IsListening) { $context = $listener.GetContext(); $response = $context.Response; $content='<html><body><H1>Red Hat OpenShift + Windows Container Workloads</H1></body></html>'; $buffer = [System.Text.Encoding]::UTF8.GetBytes($content); $response.ContentLength64 = $buffer.Length; $response.OutputStream.Write($buffer, 0, $buffer.Length); $response.Close(); };
        securityContext:
          windowsOptions:
            runAsUserName: "ContainerAdministrator"
      nodeSelector:
        beta.kubernetes.io/os: windows

Note

When using the mcr.microsoft.com/powershell:<tag> container image, you must define the command as pwsh.exe. If you are using the mcr.microsoft.com/windows/servercore:<tag> container image, you must define the command as powershell.exe. For more information, see Microsoft’s documentation.

5.4. Scaling a machine set manually

If you must add or remove an instance of a machine in a machine set, you can manually scale the machine set.

This guidance is relevant to fully automated, installer-provisioned infrastructure installations. Customized, user-provisioned infrastructure installations does not have machine sets.

Prerequisites

  • Install an OpenShift Container Platform cluster and the oc command line.
  • Log in to oc as a user with cluster-admin permission.

Procedure

  1. View the machine sets that are in the cluster:

    $ oc get machinesets -n openshift-machine-api

    The machine sets are listed in the form of <clusterid>-worker-<aws-region-az>.

  2. Scale the machine set:

    $ oc scale --replicas=2 machineset <machineset> -n openshift-machine-api

    Or:

    $ oc edit machineset <machineset> -n openshift-machine-api

    You can scale the machine set up or down. It takes several minutes for the new machines to be available.

Chapter 6. Windows node upgrades

You can ensure your Windows nodes have the latest updates by upgrading the Windows Machine Config Operator (WMCO).

6.1. Windows Machine Config Operator upgrades

When a new version of the Windows Machine Config Operator (WMCO) is released that is compatible with the current cluster version, the Operator is upgraded based on the upgrade channel and subscription approval strategy it was installed with when using the Operator Lifecycle Manager (OLM). The WMCO upgrade results in the Kubernetes components in the Windows machine being upgraded.

For a non-disruptive upgrade, the WMCO terminates the Windows machines configured by the previous version of the WMCO and recreates them using the current version. This is done by deleting the Machine object, which results in the drain and deletion of the Windows node. To facilitate an upgrade, the WMCO adds a version annotation to all the configured nodes. During an upgrade, a mismatch in version annotation results in the deletion and recreation of a Windows machine. To have minimal service disruptions during an upgrade, the WMCO only updates one Windows machine at a time.

Important

The WMCO is only responsible for updating Kubernetes components, not for Windows operating system updates. You provide the Windows image when creating the VMs; therefore, you are responsible for providing an updated image. You can provide an updated Windows image by changing the image configuration in the MachineSet spec.

For more information on Operator upgrades using the Operator Lifecycle Manager (OLM), see Upgrading installed Operators.

Chapter 7. Removing Windows nodes

You can remove a Windows node by deleting its host Windows machine.

7.1. Deleting a specific machine

You can delete a specific machine.

Prerequisites

  • Install an OpenShift Container Platform cluster.
  • Install the OpenShift CLI (oc).
  • Log into oc as a user with cluster-admin permission.

Procedure

  1. View the machines that are in the cluster and identify the one to delete:

    $ oc get machine -n openshift-machine-api

    The command output contains a list of machines in the <clusterid>-worker-<cloud_region> format.

  2. Delete the machine:

    $ oc delete machine <machine> -n openshift-machine-api
    Important

    By default, the machine controller tries to drain the node that is backed by the machine until it succeeds. In some situations, such as with a misconfigured pod disruption budget, the drain operation might not be able to succeed in preventing the machine from being deleted. You can skip draining the node by annotating "machine.openshift.io/exclude-node-draining" in a specific machine. If the machine being deleted belongs to a machine set, a new machine is immediately created to satisfy the specified number of replicas.

Chapter 8. Disabling Windows container workloads

You can disable the capability to run Windows container workloads by uninstalling the Windows Machine Config Operator (WMCO) and deleting the namespace that was added by default when you installed the WMCO.

8.1. Uninstalling the Windows Machine Config Operator

You can uninstall the Windows Machine Config Operator (WMCO) from your cluster.

Prerequisites

  • Delete the Windows Machine objects hosting your Windows workloads.

Procedure

  1. From the Operators → OperatorHub page, use the Filter by keyword box to search for Red Hat Windows Machine Config Operator.
  2. Click the Red Hat Windows Machine Config Operator tile. The Operator tile indicates it is installed.
  3. In the Windows Machine Config Operator descriptor page, click Uninstall.

8.2. Deleting the Windows Machine Config Operator namespace

You can delete the namespace that was generated for the Windows Machine Config Operator (WMCO) by default.

Prerequisites

  • The WMCO is removed from your cluster.

Procedure

  1. Remove all Windows workloads that were created in the openshift-windows-machine-config-operator namespace:

    $ oc delete --all pods --namespace=openshift-windows-machine-config-operator
  2. Verify that all pods in the openshift-windows-machine-config-operator namespace are deleted or are reporting a terminating state:

    $ oc get pods --namespace openshift-windows-machine-config-operator
  3. Delete the openshift-windows-machine-config-operator namespace:

    $ oc delete namespace openshift-windows-machine-config-operator

Additional Resources

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