Inappropriate value for attribute "network_interface_id": string required - azure

Question

Error: Incorrect attribute value type
on resources.tf line 387, in resource "azurerm_network_interface_backend_address_pool_association" "main":*
387: network_interface_id = module.linuxservers.vm_ids
|----------------
| module.linuxservers.vm_ids is tuple with 3 elements
Inappropriate value for attribute "network_interface_id": string required
hi, i am trying to associate my 3 Azure VM to the LoadBalancer backend pool but getting below above error can you please guide me on this, my code is below.
Resource.tf
module "linuxservers" {
source = "Azure/compute/azurerm"
resource_group_name = azurerm_resource_group.main.name
vm_hostname = "Elastic"
nb_instances = 3
nb_public_ip = 0
remote_port = "22"
admin_username = var.admin_username
vm_os_publisher = "OpenLogic"
vm_os_offer = "CentOS"
vm_os_sku = "7.5"
vm_size = "Standard_D2as_v4"
ssh_key = "./putty_key.pub"
vnet_subnet_id = data.azurerm_subnet.elasticsearch.id
tags = var.tags
}
resource "azurerm_lb" "main"{
name = "Elastic_LB"
location = azurerm_resource_group.main.location
resource_group_name = azurerm_resource_group.main.name
frontend_ip_configuration{
name = "FrontEndIP"
subnet_id = data.azurerm_subnet.elasticsearch.id
}
}
resource "azurerm_lb_backend_address_pool" "main" {
resource_group_name = azurerm_resource_group.main.name
loadbalancer_id = azurerm_lb.main.id
name = "BackEndAddressPool"
}
resource "azurerm_network_interface_backend_address_pool_association" "main" {
ip_configuration_name = "Configuration-VMs"
network_interface_id = module.linuxservers.vm_ids
backend_address_pool_id = azurerm_lb_backend_address_pool.main.id
}
Module/main.tf
resource "azurerm_virtual_machine" "vm-linux" {
count = ! contains(list(var.vm_os_simple, var.vm_os_offer), "WindowsServer") && ! var.is_windows_image ? var.nb_instances : 0
name = "${var.vm_hostname}-${count.index}"
resource_group_name = data.azurerm_resource_group.vm.name
location = coalesce(var.location, data.azurerm_resource_group.vm.location)
availability_set_id = azurerm_availability_set.vm.id
vm_size = var.vm_size
network_interface_ids = [element(azurerm_network_interface.vm.*.id, count.index)]
delete_os_disk_on_termination = var.delete_os_disk_on_termination
dynamic identity {
for_each = length(var.identity_ids) == 0 && var.identity_type == "SystemAssigned" ? [var.identity_type] : []
content {
type = var.identity_type
}
}
dynamic identity {
for_each = length(var.identity_ids) > 0 || var.identity_type == "UserAssigned" ? [var.identity_type] : []
content {
type = var.identity_type
identity_ids = length(var.identity_ids) > 0 ? var.identity_ids : []
}
}
storage_image_reference {
id = var.vm_os_id
publisher = var.vm_os_id == "" ? coalesce(var.vm_os_publisher, module.os.calculated_value_os_publisher) : ""
offer = var.vm_os_id == "" ? coalesce(var.vm_os_offer, module.os.calculated_value_os_offer) : ""
sku = var.vm_os_id == "" ? coalesce(var.vm_os_sku, module.os.calculated_value_os_sku) : ""
version = var.vm_os_id == "" ? var.vm_os_version : ""
}
storage_os_disk {
name = "osdisk-${var.vm_hostname}-${count.index}"
create_option = "FromImage"
caching = "ReadWrite"
managed_disk_type = var.storage_account_type
}
dynamic storage_data_disk {
for_each = range(var.nb_data_disk)
content {
name = "${var.vm_hostname}-datadisk-${count.index}-${storage_data_disk.value}"
create_option = "Empty"
lun = storage_data_disk.value
disk_size_gb = var.data_disk_size_gb
managed_disk_type = var.data_sa_type
}
}
os_profile {
computer_name = "${var.vm_hostname}-${count.index}"
admin_username = var.admin_username
admin_password = var.admin_password
custom_data = var.custom_data
}
}
}
tags = var.tags
boot_diagnostics {
enabled = var.boot_diagnostics
storage_uri = var.boot_diagnostics ? join(",", azurerm_storage_account.vm-sa.*.primary_blob_endpoint) : ""
}
}
module/output.tf
output "vm_ids" {
description = "Virtual machine ids created."
value = concat(azurerm_virtual_machine.vm-windows.*.id, azurerm_virtual_machine.vm-linux.*.id)
}
output "network_security_group_id" {
description = "id of the security group provisioned"
value = azurerm_network_security_group.vm.id
}
output "network_security_group_name" {
description = "name of the security group provisioned"
value = azurerm_network_security_group.vm.name
}
output "network_interface_ids" {
description = "ids of the vm nics provisoned."
value = azurerm_network_interface.vm.*.id
}
output "network_interface_private_ip" {
description = "private ip addresses of the vm nics"
value = azurerm_network_interface.vm.*.private_ip_address
}

Answer 1

You need to configure it for each element from 'ids` so it should be like:
resource "azurerm_network_interface_backend_address_pool_association" "main" {
count = var.node_count
ip_configuration_name = "Configuration-VMs-${count.index}"
network_interface_id = element(module.linuxservers.vm_ids, count.index)
backend_address_pool_id = azurerm_lb_backend_address_pool.main.id
}
I'm not sure about syntax here element(module.linuxservers.vm_ids, count.index), because I don't see where this output is defined (maybe I'm blind). But this is pretty much what you need.