Azure Kubernetes Service

Overview

This section presents some pointers on setting up and managing a Kubernetes cluster tailored for WorkflowGen in Azure.

Creating a new cluster

To create a new cluster that supports Linux and Windows workloads, see the Microsoft article, which includes step-by-step instructions on how to create the cluster. Follow all the instructions, including creating a Windows node pool. At the end, you should have at least two nodes: a Linux node and a Windows node.

You can use Azure Active Directory to authenticate and authorize users in the cluster. See the Microsoft article for more information.

Managing Windows and Linux nodes

By default, AKS doesn't restrict further Windows nodes from preventing Linux deployment on them. It's recommended to use to avoid problems with Linux deployment being scheduled to Windows nodes. The following is an example of how you can use taints and tolerations to manage hybrid deployments.

Taint all Windows nodes

Tainting all Windows nodes will prevent any deployment to Windows nodes from being scheduled except when it has the required toleration. Therefore, for many Linux Helm charts that don't have a node selector, the deployments to Linux nodes will automatically be scheduled. Google Kubernetes Engine does this by default. Execute the following command to taint a Windows node:

Add tolerations to Windows deployments

To be able to deploy Windows pods to Windows nodes, you have to use a combination of tolerations and node selectors in your deployment specification. For example, consider this WorkflowGen deployment:

In order for it to be scheduled to a Windows node, you would have to add the following to the template's spec:

This adds a toleration for the taint that you've just added to the node and tells the Kubernetes scheduler to select a Windows node when scheduling the WorkflowGen pods.

You can also simplify this by creating a RuntimeClass object that holds this information and referencing the runtime class in your Windows deployments:

Apply this file:

Then, add the following to the template's spec:

As you can see, this RuntimeClass also ensures that the deployment will be on a Windows LTSC 2019 (1809) node.

Managing node updates

There are two things that you must consider for update management: the Kubernetes version and the operating system update. For information on upgrading the cluster to a specific Kubernetes version, see .

Applying security patches and updating operating systems differ for Linux and Windows nodes. To get started with operating system updates, see for more information. (Don't worry about the title of the article; there's a paragraph about Windows updates in it.)

Automatically scaling node pools

You can use an autoscaler in AKS to automatically scale up the number of nodes in your cluster based on rules to keep up with demands. See for more information. This feature pairs well with the Kubernetes horizontal pod autoscaler. See for more information.

You can also use Azure Container Instances to quickly scale up your cluster for a short period of time. See for more information.