Conditional Deployments with ARM Templates | Azure ARM Tutorial

Welcome to the tutorial on performing conditional deployments with ARM templates in Azure Resource Manager. ARM templates provide a powerful way to define and deploy infrastructure and applications in Azure. With conditional deployments, you can control the creation and configuration of resources based on specific conditions, making your deployments more flexible and adaptable.

1. Defining Conditions

Conditions in ARM templates allow you to specify criteria that determine whether a resource should be deployed. You can define conditions based on template parameters, variables, or even the existence of other resources.


"parameters": {
  "deployResource": {
    "type": "bool",
    "defaultValue": false
  }
},
"resources": [
  {
    "condition": "[parameters('deployResource')]",
    "type": "Microsoft.Storage/storageAccounts",
    "name": "myStorageAccount",
    "apiVersion": "2021-04-01",
    ...
  }
]

2. Using Conditions

Conditions are evaluated during the deployment process, and resources with conditions that evaluate to false are not created or updated.


"resources": [
  {
    "type": "Microsoft.Compute/virtualMachines",
    "name": "myVM",
    "apiVersion": "2021-03-01",
    ...
    "properties": {
      "storageProfile": {
        "osDisk": {
          "vhdContainers": [
            {
              "condition": "[equals(parameters('deployResource'), true)]",
              "name": "https://mystorageaccount.blob.core.windows.net/vhds"
            }
          ]
        }
      }
    },
    ...
  }
]

3. Steps to Perform Conditional Deployments

Follow these steps to perform conditional deployments using ARM templates:

Step 1: Define Conditions

Specify conditions based on template parameters, variables, or resource existence within the ARM template.


"parameters": {
  "deployResource": {
    "type": "bool",
    "defaultValue": false
  }
},
...
"resources": [
  {
    "condition": "[parameters('deployResource')]",
    ...
  }
]

Step 2: Evaluate Conditions

During the deployment process, conditions are evaluated, and resources with conditions that evaluate to false are skipped.


"resources": [
  {
    "type": "Microsoft.Compute/virtualMachines",
    "name": "myVM",
    ...
    "properties": {
      "storageProfile": {
        "osDisk": {
          "vhdContainers": [
            {
              "condition": "[equals(parameters('deployResource'), true)]",
              ...
            }
          ]
        }
      }
    },
    ...
  }
]

Mistakes to Avoid

Not properly defining conditions and their evaluation criteria.
Forgetting to specify conditions for resources that require conditional deployment.
Using incorrect syntax or functions in condition expressions.

Frequently Asked Questions (FAQs)

Q: Can I use conditions to update existing resources?
A: No, conditions only control the creation of resources during deployment. To update existing resources, you need to use separate mechanisms like Azure PowerShell or Azure CLI.
Q: Can I use complex expressions for conditions?
A: Yes, conditions can include complex expressions using logical operators like and, or, and not. You can combine multiple conditions to create more sophisticated deployment logic.
Q: Can I use conditions for resource deletion?
A: No, conditions in ARM templates are used for resource creation or update. If you want to delete resources, you can use Azure PowerShell, Azure CLI, or the Azure portal.
Q: Are conditions evaluated at deployment time or during template validation?
A: Conditions are evaluated at deployment time, allowing you to dynamically control resource creation based on the specified conditions.
Q: Can I use conditions for cross-resource dependencies?
A: Yes, conditions can be used to define dependencies between resources. By setting conditions on resources based on the existence of other resources, you can control the order of resource creation.

Summary

In this tutorial, you learned how to perform conditional deployments using ARM templates in Azure Resource Manager. Conditions provide a powerful mechanism to control the creation and configuration of resources based on specific criteria. By leveraging conditional deployments, you can create more flexible and adaptable ARM templates for your Azure deployments.