Provisioning an Azure Web App using Terraform

In this tutorial, we'll walk through the steps to provision an Azure Web App using Terraform. Terraform is an open-source infrastructure as a code tool that allows you to define and manage your infrastructure in a declarative way.

Prerequisites

Before you begin, you'll need the following:

• Azure account
• Terraform installed on your local machine
• Azure CLI installed on your local machine

Creating a Service Principal for Terraform in Azure

When working with Terraform on Azure, you'll need a "Service Principal" for authentication. A "Service Principal" is an identity created to be used with applications, hosted services, and automated tools to access Azure resources.

To create a service principal, run the following command in the Azure CLI:

1. Login to Azure CLI

   Before you begin, make sure you are logged into your Azure account with the Azure CLI:

   az login
   

2. Set your Subscription:

   If you have multiple Azure subscriptions, specify the one you intend to use:

   az account set --subscription="YOUR_SUBSCRIPTION_ID"
   

3. Create the Service Principal:

   The following command will create a service principal. Replace YOUR_APP_NAME with a suitable name for your application:

   az ad sp create-for-rbac --name "YOUR_APP_NAME" --role contributor --scopes /subscriptions/YOUR_SUBSCRIPTION_ID
   

   Replace YOUR_SUBSCRIPTION_ID with your subscription id.

   The output of this command will provide the appId, displayName, name, password, and tenant. It's crucial to note these values, especially appId (Client ID) and password (Client Secret), as you'll need them for Terraform authentication.

4. Specify the service principal credentials in environment variables

   bash:

   export ARM_SUBSCRIPTION_ID="<azure_subscription_id>"
   export ARM_TENANT_ID="<azure_subscription_tenant_id>"
   export ARM_CLIENT_ID="<service_principal_appid>"
   export ARM_CLIENT_SECRET="<service_principal_password>"
   

   To execute the ~/.bashrc script, run source ~/.bashrc (or its abbreviated equivalent . ~/.bashrc). You can also exit and reopen Cloud Shell for the script to run automatically. Run the following bash command to verify the Azure environment variables:

   . ~/.bashrc
   

   powershell:

   $env:ARM_SUBSCRIPTION_ID="<azure_subscription_id>"
   $env:ARM_TENANT_ID="<azure_subscription_tenant_id>"
   $env:ARM_CLIENT_ID="<service_principal_appid>"
   $env:ARM_CLIENT_SECRET="<service_principal_password>"
   

   Run the following PowerShell command to verify the Azure environment variables:

   gci env:ARM_*
   

   Replace the values with your own.

Creating a Terraform Configuration

1. Create a new directory for your Terraform configuration files.

2. Create a new file named main.tf in the directory and add the following code:

   # Configure the Azure provider
   terraform {
     required_providers {
       azurerm = {
         source  = "hashicorp/azurerm"
         version = "~> 3.0.0"
       }
     }
     required_version = ">= 0.14.9"
   }
   provider "azurerm" {
     features {}
   }
   
   # Create the resource group
   resource "azurerm_resource_group" "rg" {
     name     = "blazorserver-app-tier-rg"
     location = "westeurope"
   }
   
   # Create the Linux App Service Plan
   resource "azurerm_service_plan" "appserviceplan" {
     name                = "blazorserver-app-tier-plan"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
     os_type             = "Linux"
     sku_name            = "B3"
   }
   
   # Create the web app, pass in the App Service Plan ID
   resource "azurerm_linux_web_app" "authserver" {
     name                  = "authserver-blazorserver"
     location              = azurerm_resource_group.rg.location
     resource_group_name   = azurerm_resource_group.rg.name
     service_plan_id       = azurerm_service_plan.appserviceplan.id
     https_only            = true
     site_config {
       application_stack {
         dotnet_version = "6.0"
       }
       minimum_tls_version  = "1.2"
     }
     app_settings = {
       "Redis__Configuration" = azurerm_redis_cache.redis.primary_connection_string
     }
   }
   resource "azurerm_linux_web_app" "apihost" {
     name                  = "apihost-blazorserver"
     location              = azurerm_resource_group.rg.location
     resource_group_name   = azurerm_resource_group.rg.name
     service_plan_id       = azurerm_service_plan.appserviceplan.id
     https_only            = true
     site_config {
       application_stack {
         dotnet_version = "6.0"
       }
       minimum_tls_version  = "1.2"
     }
     app_settings = {
       "Redis__Configuration" = azurerm_redis_cache.redis.primary_connection_string
     }
   }
   resource "azurerm_linux_web_app" "webapp" {
     name                  = "webapp-blazorserver"
     location              = azurerm_resource_group.rg.location
     resource_group_name   = azurerm_resource_group.rg.name
     service_plan_id       = azurerm_service_plan.appserviceplan.id
     https_only            = true
     site_config {
       application_stack {
         dotnet_version = "6.0"
       }
       minimum_tls_version  = "1.2"
     }
     app_settings = {
       "Redis__Configuration" = azurerm_redis_cache.redis.primary_connection_string
     }
   }
   
   resource "azurerm_redis_cache" "redis" {
     name                = "redis-blazorserver"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
     capacity            = 0
     family              = "C"
     sku_name            = "Basic"
     enable_non_ssl_port = false
     minimum_tls_version = "1.2"
   
     redis_configuration {
       maxmemory_reserved = 2
       maxmemory_delta    = 2
       maxmemory_policy   = "volatile-lru"
     }
   }
   

3. Run terraform init to initialize the directory.

4. Run terraform plan to see the execution plan.

5. Run terraform apply to apply the changes. Write yes when prompted to confirm the deployment.

6. Wait for the deployment to complete.

7. Navigate to the web app URL to see the deployed application.

You can also see the web app URL in the output of the terraform apply command.

You have to change the dotnet version of the runtime stack according to your application. For example, if you are using .NET 7, you should change dotnet_version = "6.0" to dotnet_version = "7.0".

Destroying the Terraform Configuration

1. Run terraform destroy to destroy the created resources.

2. Type yes when prompted to confirm the destruction.