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This document describes how to manage compute (also known as worker) nodes with OpenShift Dedicated.

The majority of changes for compute nodes are configured on machine pools. A machine pool is a group of compute nodes in a cluster that have the same configuration, providing ease of management.

You can edit machine pool configuration options such as scaling, adding node labels, and adding taints.

Creating a machine pool

A default machine pool is created when you install an OpenShift Dedicated cluster. After installation, you can create additional machine pools for your cluster by using OpenShift Cluster Manager.

The compute (also known as worker) node instance types, autoscaling options, and node counts that are available to you depend on your OpenShift Dedicated subscriptions, resource quotas and deployment scenario. For more information, contact your sales representative or Red Hat support.

Prerequisites
  • You created an OpenShift Dedicated cluster.

Procedure
  1. Navigate to OpenShift Cluster Manager and select your cluster.

  2. Under the Machine pools tab, click Add machine pool.

  3. Add a Machine pool name.

  4. Select a Worker node instance type from the drop-down menu. The instance type defines the vCPU and memory allocation for each compute node in the machine pool.

    You cannot change the instance type for a machine pool after the pool is created.

  5. Optional: Configure autoscaling for the machine pool:

    1. Select Enable autoscaling to automatically scale the number of machines in your machine pool to meet the deployment needs.

      The Enable autoscaling option is only available for OpenShift Dedicated if you have the capability.cluster.autoscale_clusters subscription. For more information, contact your sales representative or Red Hat support.

    2. Set the minimum and maximum node count limits for autoscaling. The cluster autoscaler does not reduce or increase the machine pool node count beyond the limits that you specify.

      • If you deployed your cluster using a single availability zone, set the Minimum and maximum node count. This defines the minimum and maximum compute node limits in the availability zone.

      • If you deployed your cluster using multiple availability zones, set the Minimum nodes per zone and Maximum nodes per zone. This defines the minimum and maximum compute node limits per zone.

        Alternatively, you can set your autoscaling preferences for the machine pool after the machine pool is created.

  6. If you did not enable autoscaling, select a compute node count:

    • If you deployed your cluster using a single availability zone, select a Worker node count from the drop-down menu. This defines the number of compute nodes to provision to the machine pool for the zone.

    • If you deployed your cluster using multiple availability zones, select a Worker node count (per zone) from the drop-down menu. This defines the number of compute nodes to provision to the machine pool per zone.

  7. Optional: Add node labels and taints for your machine pool:

    1. Expand the Edit node labels and taints menu.

    2. Under Node labels, add Key and Value entries for your node labels.

    3. Under Taints, add Key and Value entries for your taints.

    4. For each taint, select an Effect from the drop-down menu. Available options include NoSchedule, PreferNoSchedule, and NoExecute.

      Alternatively, you can add the node labels and taints after you create the machine pool.

  8. Optional: If you deployed OpenShift Dedicated on AWS using the Customer Cloud Subscription (CCS) model, use Amazon EC2 Spot Instances if you want to configure your machine pool to deploy machines as non-guaranteed AWS Spot Instances:

    1. Select Use Amazon EC2 Spot Instances.

    2. Leave Use On-Demand instance price selected to use the on-demand instance price. Alternatively, select Set maximum price to define a maximum hourly price for a Spot Instance.

      For more information about Amazon EC2 Spot Instances, see the AWS documentation.

      Your Amazon EC2 Spot Instances might be interrupted at any time. Use Amazon EC2 Spot Instances only for workloads that can tolerate interruptions.

      If you select Use Amazon EC2 Spot Instances for a machine pool, you cannot disable the option after the machine pool is created.

  9. Click Add machine pool to create the machine pool.

Verification
  • Verify that the machine pool is visible on the Machine pools page and the configuration is as expected.

Scaling compute nodes manually

If you have not enabled autoscaling for your machine pool, you can manually scale the number of compute (also known as worker) nodes in the pool to meet your deployment needs.

Prerequisites
  • You created an OpenShift Dedicated cluster.

  • You have an existing machine pool.

Procedure
  1. Navigate to OpenShift Cluster Manager and select your cluster.

  2. Under the Machine pools tab, click the options menu kebab for the machine pool that you want to scale.

  3. Select Scale.

  4. Specify the node count:

    • If you deployed your cluster using a single availability zone, specify the Node count in the drop-down menu.

    • If you deployed your cluster using multiple availability zones, specify the Node count per zone in the drop-down menu.

      Your subscription determines the number of nodes that you can select.

  5. Click Apply to scale the machine pool.

Verification
  • Under the Machine pools tab, verify that the Node count for your machine pool is as expected.

Adding node labels to a machine pool

Add or edit labels for compute (also known as worker) nodes at any time to manage the nodes in a manner that is relevant to you. For example, you can assign types of workloads to specific nodes.

Labels are assigned as key-value pairs. Each key must be unique to the object it is assigned to.

Adding node labels to an existing machine pool adds the labels to only new nodes that are created in that pool. The labels are not applied to the existing nodes. If you need nodes with the labels, you can scale down the nodes in the machine pool to zero, add the node labels, and then scale back up to the desired amount. Alternatively, you can create a new machine pool and define the node labels at creation time. You cannot scale the default machine pool to zero.

Prerequisites
  • You created an OpenShift Dedicated cluster.

  • You have an existing machine pool.

Procedure
  1. Navigate to OpenShift Cluster Manager and select your cluster.

  2. Under the Machine pools tab, click the options menu kebab for the machine pool that you want to add a label to.

  3. Select Edit labels.

  4. If you have existing labels in the machine pool that you want to remove, select x next to the label to delete it.

  5. Add a label using the format <key>=<value> and press enter. For example, add app=db and then press enter. If the format is correct, the key value pair is then highlighted.

  6. Repeat the previous step if you want to add additional labels.

  7. Click Save to apply the labels to the machine pool.

Verification
  1. Under the Machine pools tab, select > next to your machine pool to expand the view.

  2. Verify that your labels are listed under Labels in the expanded view.

Adding taints to a machine pool

You can add taints for compute (also known as worker) nodes in a machine pool to control which pods are scheduled to them. When you apply a taint to a machine pool, the scheduler cannot place a pod on the nodes in the pool unless the pod specification includes a toleration for the taint.

Adding taints to an existing machine pool adds the taints to only new nodes that are created in that pool. The taints are not applied to the existing nodes. If you need nodes with the taint, you can scale down the nodes in the machine pool to zero, add the taints, and then scale back up to the desired amount. Alternatively, you can create a new machine pool and define the taints at creation time. You cannot scale the default machine pool to zero.

Prerequisites
  • You created an OpenShift Dedicated cluster.

  • You have an existing machine pool.

Procedure
  1. Navigate to OpenShift Cluster Manager and select your cluster.

  2. Under the Machine pools tab, click the options menu kebab for the machine pool that you want to add a taint to.

  3. Select Edit taints.

  4. Add Key and Value entries for your taint.

  5. Select an Effect for your taint from the drop-down menu. Available options include NoSchedule, PreferNoSchedule, and NoExecute.

  6. Select Add taint if you want to add more taints to the machine pool.

  7. Click Save to apply the taints to the machine pool.

Verification
  1. Under the Machine pools tab, select > next to your machine pool to expand the view.

  2. Verify that your taints are listed under Taints in the expanded view.