list to string migration in loadbalancer backend pools

[mbrancato]

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Terraform Version

Terraform v0.11.10
+ provider.azurerm v1.17.0
+ provider.random v1.3.1
+ provider.template v1.0.0

Affected Resource(s)

• azurerm_network_interface
• azurerm_network_interface_backend_address_pool_association

Terraform Configuration Files

I have a module with now deprecated code like this:

resource "azurerm_network_interface" "vm" {
  count                     = "${var.nb_instances}"
  name                      = "${var.vm_hostname}-${count.index}-nic"
  location                  = "${var.location}"
  resource_group_name       = "${var.resource_group_name}"
  network_security_group_id = "${azurerm_network_security_group.vm.id}"

  ip_configuration {
    name                          = "ipconfig${count.index}"
    subnet_id                     = "${var.vnet_subnet_id}"
    private_ip_address_allocation = "Dynamic"
    load_balancer_backend_address_pools_ids = ["${var.lb_backend_pool_ids}"]
  }
}

Expected Behavior

I want to be able to do the following to migrate to the new pool association resource.

resource "azurerm_network_interface_backend_address_pool_association" "vm" {
  count                    = "${var.nb_instances}"
  network_interface_id     = "${element(azurerm_network_interface.vm.*.id,count.index)}"
  ip_configuration_name    = "ipconfig${count.index}"
  backend_address_pool_ids = ["${var.lb_backend_pool_ids}"]
}

Actual Behavior

The azurerm_network_interface_backend_address_pool_association resource however has moved to a string for singular backend pools, and does not allow a list to be provided. This normally in other code would need a nested loop, but we don't have that here. There is probably a way with some creative math (${var.nb_instances * length(var.lb_backend_pool_ids)} etc.) to accomplish this, but that seems overly complex.

Steps to Reproduce

1. terraform apply

References

• New Resources: azurerm_network_interface_(backend_address_pool|nat_rule)_association #2079

[magodo]

@mbrancato Thank you for this issue!
Unfortunately, terraform core doesn't correctly model count = X * Y resources, whilst it should.
I hope you don't mind that I close this issue for now.

[mbrancato]

@magodo To be clear (and I know this code is old), it has nothing to do with the count field or multiplication.

[magodo]

From your config, I assume you want to bind the same list of the backend pool id to multiple nic, in which case it is a X*Y cases, which is not supported by core for now.

[mbrancato]

@magodo no, that was not the intent. The original config is mapping a list of backend pools to a single interface. This list is already built, there is no recursion / looping in core needed here AFAIK.

In the migration from azurerm_network_interface to breaking out azurerm_network_interface_backend_address_pool_association as a separate resource, the field load_balancer_backend_address_pools_ids was a list and supported multiple backend address pools and become backend_address_pool_id as a string representing a single backend pool.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 hashibot-feedback@hashicorp.com. Thanks!