CLOUD SOLUTIONS

Azure DevOps Self-Hosted Agents Terraform

GitHub

https://github.com/cloudelementsca/ado-agents

Introduction

This guide provides instructions to setup self-hosted agents on your Azure DevOps project using the code contained in our GitHub repo.

By default, Microsoft-hosted agents only allow you to run one parallel job and up to 1800 job minutes per month, and buying more is the only option to increase this limit. While using self-hosted agents doesn't allow you to run more parallel jobs by default, it will allow you run as many parallel jobs as you have Visual Studio Enterprise Subscriptions, and it removes the 1800 minutes/month restriction.

In our solution, Terraform is used to create the infrastructure to support the self-hosted agents. Azure DevOps pipelines are used to automate the startup and shutdown of the self-hosted agents. The provided terraform code will deploy Azure Container Registry, a vnet and subnet required for Azure Container Instance (ACI), and an ACI Container Group for each type of agent image.

Each agent is based on a container image built from a Dockerfile running with Microsoft provided script to register with Azure DevOps project. Agents can be customized with different components and tools based on your requirements.

Prerequisites

Docker:

Azure DevOps Project:

Azure Resource Group:

Knowledge of, and Experience with Terraform:

Guide

Prepare Agent Pool and Pipeline

1. Import the GitHub repo into your ADO project: https://github.com/cloudelementsca/ado-agents.git

Import a Git repo

2. Create a new Agent Pool. In ADO, open Project Settings, Agent Pool, then select Add Pool to create a new agent pool for our self-hosted agent.

3. Create a new personal access token:

In Scopes section, make sure the following scopes are selected

Create PAT

4. Create variables group named 'ado-agents' replace the variables:

variable group

5. Add a pipeline to build the agent using existing YAML file: /pipelines/build-agent-images.yml

6. Add two pipeline variables to indicate how many Windows and Linux agents you would like to stand up.

Pipeline variables

Configure Terraform for ACR and Agent Deployment

7. Configure Terrraform variables in *.tfvars files for Azure Container Registry (ACR) and Azure Container Instances

In /terraform/acr/acr.auto.tfvars, update the following variables

    
        // resource group
        rg = {
          name     = "SelfHostedAgentRg"
          location = "canadacentral"
        }
        
        //  Azure Container Registry
        acr = {
          name = "cloudelementsacr"
          sku  = "Standard"
        }

In /terraform/agents/aci.auto.tfvars and data.auto.tfvars, replace the values in the following variables:

    
        // virtual network
        aci_vnet = {
          name          = "agentvnet"
          address_space = ["192.168.1.0/24"]
          rg_key        = "agentrg"
        }

        // aci subnet
        aci_subnet = {
          name             = "AgentContainerSubnet"
          address_prefixes = ["192.168.1.160/27"]
          rg_key           = "agentrg"
          delegation = {
            name                    = "aci-delegation"
            service_delegation_name = "Microsoft.ContainerInstance/containerGroups"
            actions                 = ["Microsoft.Network/virtualNetworks/subnets/action"]
          }
        }

        // Container Group Configurations - windows agent
        windowsCg = {
          name            = "winagent-co"
          location        = "canadacentral"
          rgname          = "SelfHostedAgentRg"
          os_type         = "Windows"
          ip_address_type = "Public"
          container = {
            name     = "winagent"
            image    = "cloudelementsacr.azurecr.io/winagent:latest"
            cpu      = 1
            memory   = 4
            port     = 443
            protocol = "TCP"
          }
          azure_devops_org_url  = "__AZP_URL__"
          personal_access_token = "__PERSONAL_ACCESS_TOKEN__"
          agent_pool_name       = "__AZP_POOL__"
          number_of_agents      = __NUMBER_OF_WINDOWS_AGENT__
        }

        // Container Group Configurations - linux agent
        linuxCg = {
          name            = "linuxagent-co"
          location        = "canadacentral"
          rgname          = "SelfHostedAgentRg"
          os_type         = "Linux"
          ip_address_type = "Public"
          container = {
            name     = "linuxagent"
            image    = "cloudelementsacr.azurecr.io/linuxagent:latest"
            cpu      = 1
            memory   = 4
            port     = 443
            protocol = "TCP"
          }
          azure_devops_org_url  = "__AZP_URL__"
          personal_access_token = "__PERSONAL_ACCESS_TOKEN__"
          agent_pool_name       = "__AZP_POOL__"
          number_of_agents = __NUMBER_OF_LINUX_AGENT__
        }

8. Run the pipeline to deploy Azure Container Registry, Build agent images, and deploy the Self-hosted Agents

Notes

References