Deploying Windows Virtual Desktop host pools with Terraform

Terraform is a tool that enables you to completely automate infrastructure builds through configuration files. It provides versioning for configurations, which makes it easy to deploy and maintain your existing Windows Virtual Desktop deployments on Microsoft Azure.

The following guide below describes how to deploy a new host pool or modify an existing host pool within Windows Virtual Desktop using Terraform.

Note: Terraform is an open source tool hosted in GitHub. As such, it is published "as is" with no implied support from Microsoft or any other organization. However, we would like to welcome you to open issues using GitHub issues to collaborate toward future improvements to the tool. Special thanks to Matt Betts for his major contribution.

Overview and requirements

The steps listed below must be completed in order to deploy a Windows Virtual Desktop host pool with Terraform.

1. Ensure that you meet the requirements for Windows Virtual Desktop.
   1. DC/AAD DS
   2. WVD tenant must be created
   3. TenantCreator role must be assigned
   4. VNET configured with Layer 3 access to DC/AAD DS
2. Terraform must be installed and configured as outlined here.
3. Terraform code from GitHub repository is downloaded to a local folder.
4. Terraform files variables.tf and variables_tags.tf are update.
5. Terraform deployment is started. A sample process for deploying available here.
   1. terraform init
   2. terraform plan
   3. terraform apply
6. Validate session host VMs are deployed and heart beating via Get-RdsSessionHost.

Setting up Terraform 

When you are new to Terraform. Please have a look at this article outlines the steps needed to get started with Visual Studio Code, Terraform and Azure.

Preparing Azure subscription and WVD for Terraform

Preparing the Azure subscription mean that we need to make sure that the account we are going to be used has the necessary permission to deploy new resources. Additionally, prior to updating the Terraform scripts create a resource group that will be tied to the Terraform deployment.

When it comes to WVD the preparation steps cover:

• Granting TenantCreator to the user account we are going to be using
• Creating a WVD tenant

Getting access to Terraform templates

To start all files that are listed in the folder must be downloaded to a local folder. All Terraform files needed for deployment are available at this repository.

Below is a brief description for each file and its purpose.

Availability_set.tf

This file contains the setting needed to set the availability set of VMs. In most basic deployments this file does not require changes.

Outputs.tf

This file displays certain variables that should be captured at the end of the execution. A detailed description of outputs in Terraforms can be found here. In most basic deployments this file does not require changes.

Variables.tf

This file contains all the modifiable input variables that define the behavior and outcome of running terraforms.

Variables_tags.tf

This file contains can be used to define custom tags as they are used throughout Terraforms. In most basic deployments this file does not require changes. This document outlines the benefits of using tags.

Virtual_machine.tf

This file contains code needed for setting up the individual VMs and their configuration. In most basic deployments this file does not require changes.

Virtual_machine_extensions.tf

This file contains code needed for running the customer script extensions that perform:

• Domain join
• Registration of the VM with the WVD service.

Configuring Terraform

Prior to running the Terraform variables.tf must be modified to reflect your environment. The table that follows outlines each input parameter and what is to be set to when deploying Windows Virtual Desktop.

Deploying with Terraform

This is the main section of this document as it covers the core steps needed to deploy WVD host pool with Terraform:

1. Download or “fork” all Terraform scripts in a local directory.
2. Open Visual Studio Code (VSC) and select File > Open Folder, and then point to the local folder where Terraform scripts have been downloaded.
3. Update variables.tf.
4. In VSC press Ctrl + Shift + P and select Azure Terraform: Init
5. Once this completes Ctrl + Shift + P and select Azure Terraform: Init
6. Press Ctrl + Shift + P and select Azure Terraform: Plan
7. Review the generated plan
8. Press Ctrl + Shift + P and select
9. Azure Terraform: Apply

Troubleshooting Terraform deployment

Terraform deployment can fail in two main categories:

1. Issues with Terraform code
2. Issues with Desired State Configuration (DSC)

Issues with Terraform code

While it is rare to have issues with the Terraform code it is still possible, however most often errors are due to bad input in variables.tf.

• If there are errors in the Terraform code, please file a GitHub issue.
• If there are warning in the Terraform code feel free to ignore or address for your own instance of that code.
• Using Terraform error messages it's a good starting point towards identifying issues with input variables
  

Issues with DSC

To troubleshoot this type of issue, navigate to the Azure portal and if needed reset the password on the VM that failed DSC. Once you are able to log in to the VM review the log files in the following two folders:

Note: XXX, YY, and ZZ are version numbers that will change based.

• C:\Packages\Plugins\Microsoft.Compute.CustomScriptExtension\XXX\Downloads\YY
• C:\WindowsAzure\Logs\Plugins\Microsoft.Compute.CustomScriptExtension\ZZZ

To walk you through the processes outlined in this post, please watch my video tutorial: