Dynamic Conditional Block - Missing required argument

Terraform
1

I’ve got a custom module that I have created to build an Azure VM using azurerm_windows_virtual_machine and want to have a dynamic donditional block depending on if var.vm_image_custom_id is supplied.

If var.vm_image_custom_id is supplied, I want it to use ‘source_image_id’ if it isn’t I want to use a block ‘source_image_reference’ which is populated with publisher, offer etc.

Here is the code;

resource "azurerm_windows_virtual_machine" "main" {
  tags                     = merge(var.tags)
  enable_automatic_updates = "false"
  name                     = upper("${var.vm_name}")
  resource_group_name      = data.azurerm_resource_group.main.name
  location                 = data.azurerm_resource_group.main.location
  license_type             = var.license_type
  size                     = var.vm_size
  admin_username           = var.vm_username
  admin_password           = var.vm_password
  patch_mode               = "Manual"
  zone                     = var.vm_availability_zone
  network_interface_ids = [
    azurerm_network_interface.main.id,
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = var.vm_os_disk_type
  }

  source_image_id = var.vm_image_custom_id != null ? var.vm_image_custom_id : null

  dynamic "source_image_reference" {
    for_each = var.vm_image_custom_id == null ? toset([1]) : toset([])
    content {
      publisher  = var.vm_image_publisher 
      offer      = var.vm_image_offer 
      sku        = var.vm_image_sku 
      version    = var.vm_image_version
    }

}

It works if I supply an var.vm_image_custom_id but doesn’t if I don’t, this is the error I get;

image
image915×252 11.7 KB

It think my syntax is wrong but I can’t get my head around it :frowning:

2

Hi,

I noticed you are using toset() function in your for_each:

I think this might be the reason for your error, could you test it this way?

for_each = var.vm_image_custom_id == null ? [1] : []

Daniel

3

Yeah I tried that before using toSet but got the same error.

Does the syntax look right to you?

4

Yeah, it does.

Could you share here the four variables block you have in that dynamic block?

5

Yes of course, this is the variables.tf for the custom module

variable "vm_image_custom_id" {
  description = "Specify a custom image instead of a market place image (Optional)"
  default = null
}

variable "vm_image_publisher" {
  description = "Market Place - The image publisher of the Virtual machine e.g. MicrosoftWindowsServer"
  default = null
}

variable "vm_image_offer" {
  description = "Market Place - The image offer of the Virtual machine e.g. WindowsServer"
  default = null
}

variable "vm_image_sku" {
  description = "Market Place - The image sku of the Virtual machine e.g. 2019-Datacenter"
  default = null
}

Then I am calling the module from main.tf

module "corporate-servers" {
  source                        = "../../modules/tf_azurerm_virtual_machine"
  for_each                      = var.corporate-servers
  rg_name                       = var.rg_name
  vm_name                       = each.value["vm_name"]
  license_type                  = var.license_type
  data_subnet_name              = each.value["data_subnet_name"]
  data_vnet                     = var.data_vnet
  data_vnet_rg                  = var.data_vnet_rg
  vm_size                       = each.value["vm_size"]
  vm_password                   = var.vm_admin_password
  vm_availability_zone          = each.value["vm_availability_zone"]
  vm_image_publisher            = var.vm_image_publisher
  vm_image_offer                = var.vm_image_offer
  vm_image_sku                  = var.vm_image_sku
  vm_image_custom_id            = each.value["vm_image_custom_id"]
  enable_accelerated_networking = var.enable_accelerated_networking
  vm_require_data_disk          = each.value["vm_require_data_disk"]
  vm_data_disk_size             = each.value["vm_data_disk_size"]
  vm_ou_path                    = var.vm_ou_path
  vm_add_to_domain_password     = var.vm_domain_password
  tags                          = var.common_tags

  depends_on = [
    azurerm_resource_group.main,
  ]
  
}

This is the terrafrom.tfvars

rg_name = "rg-corp-servers"

corporate-servers = {
  SVR1 = {
    vm_name                          = "SVR1"
    data_subnet_name                 = "subnet-common"
    vm_availability_zone             = "1"
    vm_size                          = "Standard_B2ms"
    vm_require_data_disk             = false
    vm_data_disk_size                = null
    vm_image_custom_id               = "/subscriptions/xxxxsubscriptionidxxxx/resourceGroups/rg-image/providers/Microsoft.Compute/images/live-server-image"
  }
  
  SVR2 = {
      vm_name                          = "SVR2"
      data_subnet_name                 = "subnet-common"
      vm_availability_zone             = "1"
      vm_size                          = "Standard_D4s_v3"
      vm_require_data_disk             = true
      vm_data_disk_size                = "1024"
      vm_image_publisher               = "MicrosoftWindowsServer" 
      vm_image_offer                   = "WindowsServer"
      vm_image_sku                     =  "2019-Datacenter"
      vm_image_custom_id               = null
    } 

}

Thanks again for your help with this!

6

Don’t you have variables.tf for root level in your code?