Tag Archives: Scale

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Tanzu Kubernetes Grid – How to edit Node resources and Scale a Cluster Vertically With kubectl

In this blog post I am going to walk you through how to edit the Machine Resource configurations for nodes deployed by Tanzu Kubernetes Grid.

Example Issue – Disk Pressure

In my environment, I found I needed to alter my node resources, as several Pods were getting the evicted status in my cluster.

By running a describe on the pod, I could see the failure message was due to the node condition DiskPressure.

  • If you need to clean up a high number of pods across namespaces in your environment, see this blog post.
kubectl describe pod {name}

TKG - kubectl describe pod - failed - evicted - pod the node had condition disk pressure

I then looked at the node that the pod was scheduled too. (You can see this in the above screenshot, 4th line “node”).

Below we can see that on the node, Kubelet has tainted the node to stop further pods from being scheduled to this node.

In the events we see the message “Attempting to reclaim ephemeral-storage”

TKG - kubectl describle node - disk pressure

Configuring resources for Tanzu Kubernetes Grid nodes

First you will need to log into your Tanzu Kubernetes Grid Management Cluster, that was used to deploy the Workload (Guest) cluster. As this controls cluster deployments and holds the necessary bootstrap and machine creation configuration.

Once logged in, locate the existing VsphereMachineTemplate for your chosen cluster. Each cluster will have two configurations (one for Control Plane nodes, one for Compute plane/worker nodes).

If you have deployed TKG into a public cloud, then you can use the following types instead, and continue to follow this article as the theory is the same regardless of where you have deployed to:

  • AWSMachineTemplate on Amazon EC2
  • AzureMachineTemplate on Azure
kubectl get VsphereMachineTemplate

TKG - kubectl get VsphereMachineTemplate

You can attempt to directly alter this file, however, when trying to save the edited file, you will be presented with the following error message:

kubectl edit VsphereMachineTemplate tkg-wld-01-worker

error: vspheremachinetemplates.infrastructure.cluster.x-k8s.io "tkg-wld-01-worker" could not be patched: admission webhook "validation.vspheremachinetemplate.infrastructure.x-k8s.io" denied the request: spec: Forbidden: VSphereMachineTemplateSpec is immutable

TKG - kubectl edit VsphereMachineTemplate - Forbidden- VSphereMachineTemplateSpec is immutable

Instead, you must output the configuration to a local file and edit it. Also, you will need to remove the following fields if you are using my below method. Continue reading Tanzu Kubernetes Grid – How to edit Node resources and Scale a Cluster Vertically With kubectl


Red Hat OpenShift on VMware vSphere – How to Scale and Edit your cluster deployments

Working with Red Hat OpenShift on vSphere, I’m really starting to understand the main infrastructure components and how everything fits together.

Next up was understanding how to control the cluster size after initial deployment. So, with Red Hat OpenShift, there are some basic concepts we need to understand first, before we jump into the technical how-to’s below in this blog.

In this blog I will cover the following;

- Understanding the concepts behind controlling Machines in OpenShift
- Editing your MachineSet to control your Virtual Machine Resources
- Editing your MachineSet to scale your cluster manually
- Deleting a node
- Configuring ClusterAutoscaler to automatically scale your environment

Machine API

The Machine API is a combination of primary resources that are based on the upstream Cluster API project and custom OpenShift Container Platform resources.

The Machine API performs all node host provisioning management actions as a post cluster installation method, providing you dynamic provisioning on top of your VMware vSphere platform (and other public/private cloud platforms).

The two primary resources are:

An object that describes the host for a Node. A machine has a providerSpec, 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.
Groups of machines. MachineSets are to machines as ReplicaSets are to Pods. If you need more machines or must scale them down, you change the replicas field on the MachineSet to meet your compute need.

These custom resources add capabilities to your OpenShift cluster:

This resource automatically scales machines in a cloud. You can set the minimum and maximum scaling boundaries for nodes in a specified MachineSet, and the MachineAutoscaler 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.
This resource is based on the upstream ClusterAutoscaler project. In the OpenShift Container Platform implementation, this is integrated with the Machine API by extending the MachineSet API. You can set cluster-wide scaling limits for resources such as cores, nodes, memory, GPU, etc. You can configure priorities so that the cluster prioritizes pods so that new nodes are not brought online for less important pods. You can also set the ScalingPolicy, so that for example, you can scale up nodes but not scale down the node count.


This resource detects when a machine is unhealthy, deletes it, and, on supported platforms, creates a new machine. You can read more here about this technology preview feature in OCP 4.6.

Editing your MachineSet to control your Virtual Machine Resources

To view the current MachineSet objects available run; Continue reading Red Hat OpenShift on VMware vSphere – How to Scale and Edit your cluster deployments