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Managing compute nodes

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 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 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 Compute 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 Compute 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 Compute 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.

      Creating a machine pool with taints is only possible if the cluster already has at least one machine pool without a taint.

    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: Select additional custom security groups to use for nodes in this machine pool. You must have already created the security groups and associated them with the VPC that you selected for this cluster. You cannot add or edit security groups after you create the machine pool. For more information, see the requirements for security groups in the "Additional resources" section.

  9. 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.

  10. 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.

Deleting a machine pool

You can delete a machine pool in the event that your workload requirements have changed and your current machine pools no longer meet your needs.

You can delete machine pools using Red Hat OpenShift Cluster Manager.

Prerequisites

  • You have created an OpenShift Dedicated cluster.

  • The cluster is in the ready state.

  • You have an existing machine pool without any taints and with at least two replicas for a Single-AZ cluster or three replicas for a Multi-AZ cluster.

Procedure

  1. From OpenShift Cluster Manager, navigate to the Cluster List page and select the cluster that contains the machine pool that you want to delete.

  2. On the selected cluster, select the Machine pools tab.

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

  4. Click Delete.

The selected machine pool is deleted.

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.

You must scale each machine pool separately.

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.

Node labels

A label is a key-value pair applied to a Node object. You can use labels to organize sets of objects and control the scheduling of pods.

You can add labels during cluster creation or after. Labels can be modified or updated at any time.

Additional resources

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.

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.

A cluster must have at least one machine pool that does not contain any taints.
Prerequisites

  • You created an OpenShift Dedicated cluster.

  • You have an existing machine pool that does not contain any taints and contains at least two instances.

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.

Additional resources