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Conditional deployment in ARM templates

  • Άρθρο

Sometimes you need to optionally deploy a resource in an Azure Resource Manager template (ARM template). Use the condition element to specify whether the resource is deployed. The value for the condition resolves to true or false. When the value is true, the resource is created. When the value is false, the resource isn't created. The value can only be applied to the whole resource.

Note

Conditional deployment doesn't cascade to child resources. If you want to conditionally deploy a resource and its child resources, you must apply the same condition to each resource type.

Tip

We recommend Bicep because it offers the same capabilities as ARM templates and the syntax is easier to use. To learn more, see conditional deployments.

Deploy condition

You can pass in a parameter value that indicates whether a resource is deployed. The following example conditionally deploys a DNS zone.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "deployZone": {
      "type": "bool"
    }
  },
  "functions": [],
  "resources": [
    {
      "condition": "[parameters('deployZone')]",
      "type": "Microsoft.Network/dnsZones",
      "apiVersion": "2018-05-01",
      "name": "myZone",
      "location": "global"
    }
  ]
}

For a more complex example, see Azure SQL logical server.

New or existing resource

You can use conditional deployment to create a new resource or use an existing one. The following example shows how to either deploy a new storage account or use an existing storage account.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "storageAccountName": {
      "type": "string"
    },
    "location": {
      "type": "string",
      "defaultValue": "[resourceGroup().location]"
    },
    "newOrExisting": {
      "type": "string",
      "defaultValue": "new",
      "allowedValues": [
        "new",
        "existing"
      ]
    }
  },
  "resources": [
    {
      "condition": "[equals(parameters('newOrExisting'), 'new')]",
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2022-09-01",
      "name": "[parameters('storageAccountName')]",
      "location": "[parameters('location')]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2"
    },
    {
      "condition": "[equals(parameters('newOrExisting'), 'existing')]",
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2022-09-01",
      "name": "[parameters('storageAccountName')]"
    }
  ],
  "outputs": {
    "storageAccountId": {
      "type": "string",
      "value": "[if(equals(parameters('newOrExisting'), 'new'), resourceId('Microsoft.Storage/storageAccounts', parameters('storageAccountName')), resourceId('Microsoft.Storage/storageAccounts', parameters('storageAccountName')))]"
    }
  }
}

When the parameter newOrExisting is set to new, the condition evaluates to true. The storage account is deployed. Otherwise the existing storage account is used.

For a complete example template that uses the condition element, see VM with a new or existing Virtual Network, Storage, and Public IP.

Runtime functions

If you use a reference or list function with a resource that is conditionally deployed, the function is evaluated even if the resource isn't deployed. You get an error if the function refers to a resource that doesn't exist.

Use the if function to make sure the function is only evaluated for conditions when the resource is deployed. See the if function for a sample template that uses if and reference with a conditionally deployed resource.

You set a resource as dependent on a conditional resource exactly as you would any other resource. When a conditional resource isn't deployed, Azure Resource Manager automatically removes it from the required dependencies.

Complete mode

If you deploy a template with complete mode and a resource isn't deployed because condition evaluates to false, the result depends on which REST API version you use to deploy the template. If you use a version earlier than 2019-05-10, the resource isn't deleted. With 2019-05-10 or later, the resource is deleted. The latest versions of Azure PowerShell and Azure CLI delete the resource when condition is false.

Next steps