vSphere with Tanzu (vSphere Kubernetes Service) cluster upgrades: During a cluster upgrade why is a kubernetes cluster pause occurring?

Products

• VMware vSphere Kubernetes Service

Issue/Introduction

When a VKS cluster is upgraded, the process involves replacements of control plane nodes and worker nodes successfully. While the cluster is upgraded that Cluster object must be placed in a "paused" state.

 

This article answers the question, "Why is such a pause occurring?"

Environment

VMware vSphere with Tanzu

VMware vSphere Kubernetes Service

Resolution

Question: Why is such a pause occurring?

 

Answer:

• During a cluster upgrade event, the ability to make changes to the actual kubernetes cluster have to be paused until the upgrade completes.  
  
  
• This is necessary for maintaining accuracy of the "true state of the cluster".  
  
  
• Running workloads are not affected through the standard kubernetes pod scheduler.  
  
  
• And this can take time depending on the number of cluster nodes that the cluster has.  
  
  
• This is the standard Kubernetes upgrade lifecycle: refer to the Open Source Kubernetes Upgrade documentation
  
  
• The above is performed automatically for you by vSphere with Tanzu Supervisor.  Which is discussed in detail in the About vSphere with Tanzu Updates documentation. 
  
  
• And during that time, the cluster must be in a paused state until all cluster nodes are upgraded.