Azure DevOps Agent Pool on VM Scale Set

This repository contains infrastructure deployment scripts that can be used to create a Virtual Machine Scale Set (VMSS) running a set of DevOps build agents. Each node in the scale set is based on a VM image that can be customized to add any necessary pre-requisites. Upon node start, the DevOps agent is installed and registered in a Build Pool.

Before running the scripts below, create a resource group named vmss-build-pool; for example:

az group create -n vmss-build-pool -l westeurope

Creating the VM image

The Packer configuration can be used to build a new Azure VM Image. The image is based on Ubuntu 18.04 LTS and installs some basic build tools (build-essential, Docker, ...) The installation script used is install-build-agent.sh.

The managed image is called build-agent-image and will be created in the vmss-build-pool resource group.

packer build -force agent-image.json

Starting the VM Scale Set

azuredeploy.json is an ARM Template that will spin up a VM Scale Set based on the image created in the previous step.

To deploy it:

az group deployment create -g vmss-build-pool \
  --template-file azuredeploy.json \
  --parameters @deploy-parameters.json

Upon deployment, every node of the scale set will run start-agent.sh to configure the Azure DevOps agent. It can also perform some other initialization tasks, like pre-pulling some Docker images or pre-populating other caches.

You will need to edit deploy-parameters.json to change the deployment parameters:

• adminUsername: the name for the administrative user account created on the VM.
• adminPassword: the password for the administrative user account.
• subnetId: the resource ID of the Virtual Network subnet where the nodes will be created.
• managedImageResourceUri: the resource ID of the custom VM image to use for the nodes.
• agentOrgUrl: the URL of the Azure DevOps organization.
• agentPat: the Personal Access Token (PAT) used to configure the agent.
• agentPool: the name of the Agent Pool where the agent should register.