Azure Frontdoor Dynamic Block not working in Terraform - azure

Question

Im having some issues with coding a dynamic block for frontdoor in Terraform. I have found a good working example of one here: https://github.com/spy86/terraform-azure-front-door/blob/main/front_door.tf
Yet my frontdoor setup is not as complex as this persons and I do not need everything he has done on his.
What I am trying to achieve is to put two backend_pools on my front door to enable multiple regions. The only way to do this is to bring in dynamic blocks. Yet when I do this I am getting an error: │ Error: Unsupported attribute │ │ on frontdoor.tf line 96, in resource "azurerm_frontdoor" "jctestingfrontdoor": │ 96: for_each = var.backend_pool_settings.value.backend[*] │ ├──────────────── │ │ var.backend_pool_settings is a list of object, known only after apply │ │ Can't access attributes on a list of objects. Did you mean to access an attribute for a specific element of the list, or across all elements of the list?
Here is my Frontdoor code:
Main.tf
resource "azurerm_frontdoor" "jctestingfrontdoor" {
depends_on = [
azurerm_key_vault.jctestingenv_keyvault,
]
name = "testingfrontdoor"
resource_group_name = azurerm_resource_group.Terraform.name
routing_rule {
name = "projroutingrule"
accepted_protocols = ["Http", "Https"]
patterns_to_match = ["/*"]
frontend_endpoints = ["projfrontendendpoint", "${local.frontendendpoint2}"]
forwarding_configuration {
forwarding_protocol = "MatchRequest"
backend_pool_name = "projbackendpool"
}
}
backend_pool_load_balancing {
name = "projloadbalancesettings"
sample_size = 255
successful_samples_required = 1
}
backend_pool_health_probe {
name = "projhealthprobesettings"
path = "/health/probe"
protocol = "Https"
interval_in_seconds = 240
}
dynamic "backend_pool" {
for_each = var.backend_pool_settings[*]
content {
name = var.backend_pool_settings.name
load_balancing_name = var.backend_pool_settings.load_balancing_name
health_probe_name = var.backend_pool_settings.health_probe_name
dynamic "backend" {
for_each = var.backend_pool_settings.backend
content {
address = var.backend_pool_settings.address
host_header = var.backend_pool_settings.host_header
http_port = var.backend_pool_settings.http_port
https_port = var.backend_pool_settings.https_port
priority = var.backend_pool_settings.priority
weight = var.backend_pool_settings.weight
enabled = var.backend_pool_settings.enabled
}
}
}
}
frontend_endpoint {
name = "projfrontendendpoint"
host_name = format("testingfrontdoor.azurefd.net")
}
frontend_endpoint {
name = local.frontendendpoint2
host_name = format("portal-staging.terraform.example")
}
}
resource "azurerm_frontdoor_custom_https_configuration" "portal_staging_https_config" {
depends_on = [
azurerm_frontdoor.jctestingfrontdoor
]
frontend_endpoint_id = "${azurerm_frontdoor.jctestingfrontdoor.id}/frontendEndpoints/${local.frontendendpoint2}"
custom_https_provisioning_enabled = true
custom_https_configuration {
certificate_source = "AzureKeyVault"
azure_key_vault_certificate_secret_name = "imported-cert"
azure_key_vault_certificate_vault_id = azurerm_key_vault.jctestingenv_keyvault.id
}
}
variables.tf
variable "backend_pool_settings" {
description = "backend pool stettings for frontdoor"
type = object({
name = string
backend = list(object({
address = string
host_header = string
http_port = number
https_port = number
weight = number
priority = number
enabled = bool
}))
load_balancing_name = string
health_probe_name = string
})
}
locals.tf
locals {
frontendendpoint2 = "projfrondoordnsname"
backendpool1 = "uksouth"
backendpool2 = "westeurope"
}
inputvariables.tfvars
backend_pool_settings = (
{
name = "uksouth"
backend = {
address = "portal-staging-testing1.terraform.example"
host_header = "portal-staging-testing1.terraform.example"
http_port = 80
https_port = 443
priority = 1
weight = 50
enabled = true
}
load_balancing_name = "projloadbalancesettings"
health_probe_name = "projloadbalancesettings"
},
{
name = "westeurope"
backend = {
address = "portal-staging-testing2.terraform.example"
host_header = "portal-staging-testing2.terraform.example"
http_port = 80
https_port = 443
priority = 1
weight = 50
enabled = true
}
load_balancing_name = "projloadbalancesettings"
health_probe_name = "projloadbalancesettings"
})
I have coded the variables as object lists but I'm not sure if that's the right thing to do and I'm not sure if I should be splitting the backend_pool as two dynamic blocks like in the example.
UPDATE:
After working through my code I have simplified it a bit more,
resource "azurerm_frontdoor" "jctestingfrontdoor" {
depends_on = [
azurerm_key_vault.jctestingenv_keyvault,
]
name = "testingfrontdoor"
resource_group_name = azurerm_resource_group.Terraform.name
routing_rule {
name = "projroutingrule"
accepted_protocols = ["Http", "Https"]
patterns_to_match = ["/*"]
frontend_endpoints = ["projfrontendendpoint", "${local.frontendendpoint2}"]
forwarding_configuration {
forwarding_protocol = "MatchRequest"
backend_pool_name = "projbackendpool"
}
}
backend_pool_load_balancing {
name = "projloadbalancesettings"
sample_size = 255
successful_samples_required = 1
}
backend_pool_health_probe {
name = "projhealthprobesettings"
path = "/health/probe"
protocol = "Https"
interval_in_seconds = 240
}
backend_pool {
name = "projbackendpool"
dynamic "backend" {
for_each = var.backend_pool_settings.value.backend[*]
content {
address = backend.address
host_header = backend.host_header
http_port = backend.http_port
https_port = backend.https_port
priority = backend.priority
weight = backend.weight
enabled = backend.enabled
}
}
load_balancing_name = "projloadbalancesettings"
health_probe_name = "projhealthprobesettings"
}
frontend_endpoint {
name = "projfrontendendpoint"
host_name = format("testingfrontdoor.azurefd.net")
}
frontend_endpoint {
name = local.frontendendpoint2
host_name = format("portal-staging.terraform.example")
}
}
Now the error im getting is: │ Error: Unsupported attribute │ │ on frontdoor.tf line 96, in resource "azurerm_frontdoor" "jctestingfrontdoor": │ 96: for_each = var.backend_pool_settings.value.backend[*] │ ├──────────────── │ │ var.backend_pool_settings is a list of object, known only after apply │ │ Can't access attributes on a list of objects. Did you mean to access an attribute for a specific element of the list, or across all elements of the list?

Answer 1

I have managed to fix this by playing about with the map variable. Basically, front door does not require the object of the backend to be specified as it already knows its building a backend. Also I played around with a few bits of other code and got this working see my code for example:
mainj.tf
resource "azurerm_frontdoor" "jctestingfrontdoor" {
depends_on = [
azurerm_key_vault.jctestingenv_keyvault,
]
name = "testingfrontdoor"
resource_group_name = azurerm_resource_group.terraform.name
routing_rule {
name = "projroutingrule"
accepted_protocols = ["Http", "Https"]
patterns_to_match = ["/*"]
frontend_endpoints = ["projfrontendendpoint", "${local.frontendendpoint2}"]
forwarding_configuration {
forwarding_protocol = "MatchRequest"
backend_pool_name = "projbackendpool"
}
}
backend_pool_load_balancing {
name = "projloadbalancesettings"
sample_size = 255
successful_samples_required = 1
}
backend_pool_health_probe {
name = "projhealthprobesettings"
path = "/health/probe"
protocol = "Https"
interval_in_seconds = 240
}
backend_pool {
name = "projbackendpool"
dynamic "backend" {
for_each = var.backend_pool_settings
content {
address = backend.value.address
host_header = backend.value.host_header
http_port = backend.value.http_port
https_port = backend.value.https_port
priority = backend.value.priority
weight = backend.value.weight
enabled = backend.value.enabled
}
}
load_balancing_name = "projloadbalancesettings"
health_probe_name = "projhealthprobesettings"
}
frontend_endpoint {
name = "projfrontendendpoint"
host_name = format("testingfrontdoor.azurefd.net")
}
frontend_endpoint {
name = local.frontendendpoint2
host_name = format("portal-staging.terraform.example")
}
}
resource "azurerm_frontdoor_custom_https_configuration" "portal_staging_https_config" {
depends_on = [
azurerm_frontdoor.jctestingfrontdoor
]
frontend_endpoint_id = "${azurerm_frontdoor.jctestingfrontdoor.id}/frontendEndpoints/${local.frontendendpoint2}"
custom_https_provisioning_enabled = true
custom_https_configuration {
certificate_source = "AzureKeyVault"
azure_key_vault_certificate_secret_name = "imported-cert"
azure_key_vault_certificate_vault_id = azurerm_key_vault.jctestingenv_keyvault.id
}
}
variables.tf
variable "backend_pool_settings" {
description = "backend pool stettings for frontdoor"
type = map(object({
address = string
host_header = string
http_port = number
https_port = number
weight = number
priority = number
enabled = bool
}))
}
inputvariables.tfvars
backend_pool_settings = {
backendone = {
address = "portal-staging-testing1.terraform.example"
host_header = "portal-staging-testing1.terraform.example"
http_port = 80
https_port = 443
priority = 1
weight = 50
enabled = true
},
backendtwo = {
address = "portal-staging-testing2.terraform.example"
host_header = "portal-staging-testing2.terraform.example"
http_port = 80
https_port = 443
priority = 1
weight = 50
enabled = true
}
}
This post also helped me to figure out messing about with map objects with Terraform: https://serverfault.com/questions/1063395/terraform-values-from-tfvars-are-not-loading-when-using-multi-level-maps