Why use Azure Resource Manager templates?

  • 4 minutes

Resource Manager templates, also called Azure Resource Manager templates, are JSON files that define the infrastructure and configuration for your Azure deployments. They represent a modern approach to infrastructure as code (IaC), replacing manual and error-prone deployment processes.

The challenge with manual deployments

Provisioning infrastructure for applications has traditionally been time-consuming and manual. You would:

  • Work through portal wizards: Click through multiple screens to create each resource individually.
  • Run imperative scripts: Execute commands in a specific order, repeating for each environment.
  • Maintain outdated documentation: Struggle to keep configuration documentation synchronized with actual deployments.
  • Face stressful production deployments: Manual production deployments increase the risk of human error.

ARM templates solve these problems by providing a declarative approach where you define what resources you need, and Azure Resource Manager handles the deployment orchestration.

Reduced errors and increased reliability

  • Eliminate human errors: Remove the risk of typos, missed steps, or incorrect configurations.
  • Predictable outcomes: The same template always produces the same infrastructure state.
  • Built-in validation: Azure validates templates before deployment, catching errors early.

Complete list of ARM template advantages

Consider using Resource Manager templates when you need these benefits:

  • Improved consistency

Resource Manager templates provide a common language for describing deployments. Regardless of the tool (Azure portal, Azure CLI, PowerShell, or SDKs), the template structure, format, and expressions remain identical. This consistency ensures:

  • Cross-team collaboration: Developers and operations teams work with the same infrastructure definitions.

  • Multi-environment reliability: Development, staging, and production use the same template structure.

  • Express complex deployments clearly

Templates enable you to deploy multiple resources in the correct order automatically. For example:

  • Dependency awareness: Resource Manager won't deploy a virtual machine before creating the OS disk or network interface.

  • Automatic ordering: Dependency mapping ensures resources are created in the right sequence.

  • Visual representation: You can see all resources and their relationships in one JSON file.

  • Infrastructure as code paradigm

Templates are code that can be shared, tested, and versioned like any software:

  • Version control: Store templates in Git repositories to track all infrastructure changes.

  • Code reviews: Apply standard peer review processes to infrastructure modifications.

  • Testing: Validate templates using unit tests and automated validation tools.

  • Audit trail: Every infrastructure change is documented in version history.

  • Promote reuse through parameters

Template parameters enable creating multiple versions of infrastructure from a single template:

"parameters": {
  "environmentName": {
    "type": "string",
    "allowedValues": ["dev", "staging", "production"]
  },
  "vmSize": {
    "type": "string",
    "defaultValue": "Standard_B2s"
  }
}

Benefits:

  • Environment flexibility: Use the same template for development (small VMs) and production (large VMs).

  • Cost optimization: Pass different SKUs or sizes based on environment requirements.

  • Reduced duplication: Maintain one template instead of separate files per environment.

  • Modular and linkable templates

You can link templates together to create modular, reusable components:

  • Small, focused templates: Create templates for specific resources (networking, storage, compute).

  • Composition: Combine small templates into complete solutions.

  • Reusability: Share common components across multiple projects.

  • Maintainability: Update one module and all dependent deployments benefit.

  • Simplified orchestration

Deploy all resources with a single command:

az deployment group create \
  --resource-group myResourceGroup \
  --template-file main.json \
  --parameters @parameters.json

What happens:

  • Resource Manager analyzes all resources and dependencies.
  • Creates resources in parallel where possible.
  • Handles any deployment errors and provides detailed logs.
  • Returns when all resources are deployed successfully.

Azure Quickstart Templates

Azure Quickstart Templates provide a community-driven library of ready-to-use templates for common deployment scenarios. This open-source repository offers:

  • Hundreds of templates: Pre-built solutions for web apps, databases, virtual machines, networking, and more.
  • Best practices: Templates follow Azure recommendations and security guidelines.
  • Learning resource: Study how experienced developers structure their infrastructure code.
  • Customization starting point: Download templates and adapt them to your specific requirements.

Example use cases:

  • Deploy a WordPress site with Azure App Service and MySQL.
  • Create a Kubernetes cluster with AKS (Azure Kubernetes Service).
  • Set up a data analytics pipeline with Azure Data Factory.

Access the library: Azure Quickstart Templates on GitHub

Bicep: Modern ARM template alternative

While this module focuses on JSON ARM templates, it's important to know about Bicep, a domain-specific language for defining Azure infrastructure:

  • Cleaner syntax: Bicep provides simpler, more readable syntax compared to JSON.
  • Same capabilities: Bicep compiles to ARM templates, so you get all ARM features.
  • Better tooling: Enhanced IDE support with IntelliSense and validation.
  • Native Azure support: Fully supported by Microsoft as the recommended IaC language.

Example comparison:

// Bicep syntax (cleaner)
resource storageAccount 'Microsoft.Storage/storageAccounts@2021-02-01' = {
  name: 'mystorageaccount'
  location: 'eastus'
  sku: {
    name: 'Standard_LRS'
  }
  kind: 'StorageV2'
}

// Equivalent JSON ARM template
{
  "type": "Microsoft.Storage/storageAccounts",
  "apiVersion": "2021-02-01",
  "name": "mystorageaccount",
  "location": "eastus",
  "sku": {
    "name": "Standard_LRS"
  },
  "kind": "StorageV2"
}

When to use Bicep: For new projects, consider Bicep as your primary IaC language. For existing ARM templates, you can convert them to Bicep using the az bicep decompile command.