Create Function App using Terraform with functions extension version 4 - azure

Question

I have little problem that I am trying to solve.
I am trying to create function apps using terraform as IaC and my only problem is with functions extension version in version 4.
When I insert the variable like this:
functions_extension_version = "~4"
I get this version as custom (I am trying to create Dotnet version 6 so it must be version 4)
But when I use version 3 like this:
functions_extension_version = "~3"
it works fine
I know my app service plan is support functions extension version 4 becuase when I try to create manually it is working as expected.
Thanks
edit:
full TF code:
resource "azurerm_windows_function_app" "function_windows" {
# condition
count = var.to_create ? 1 : 0
# basic info configuration
name = var.name
resource_group_name = var.resource_group_name
location = var.location
storage_account_name = data.azurerm_storage_account.storage_account.name
storage_account_access_key = data.azurerm_storage_account.storage_account.primary_access_key
service_plan_id = var.app_service_plan_id
# function configuration
https_only = true
functions_extension_version = "~4"
site_config {
application_stack {
dotnet_version = var.runtime == "dotnet" ? var.runtime_version : null
java_version = var.runtime == "java" ? var.runtime_version : null
node_version = var.runtime == "node" ? var.runtime_version : null
}
scm_use_main_ip_restriction = true
elastic_instance_minimum = local.elastic_instance_minimum
}
identity {
type = "SystemAssigned"
}
tags = var.tags
}

Answer 1

Your app is pinned to an unsupported runtime version for ‘dotnet’. For better performance, we recommend using one of our supported versions instead: ~3.
There are no issues with your terraform code, but the issue I found is with the version running in the backend.
According to #Sandro Pereira's blog,
If you encounter this kind of error or a similar alert, it signifies that the runtime version you defined uses an unsupported version of .NET Framework. In some instances, although your
function runtime version = ~4 works with .NET framework v6.0, but it actually runs using v4.0 in the backend.
Runtime version ~3 normally runs on top of .NET Framework v4.0. However, runtime version ~4 requires .NET Framework v6.0.
By referring terraform registry, I created the replica of a function app with terraform and deployed successfully.
Code snippet:
resource "azurerm_function_app" "newfunc" {
name = "test-azure-functions"
location = azurerm_resource_group.newfunc.location
resource_group_name = azurerm_resource_group.newfunc.name
app_service_plan_id = azurerm_app_service_plan.newfunc.id
storage_account_name = "mystorage"
}
After successful deployment in Azure portal:
You can validate which version of .NET is running for your function app by checking:
Resource Explorer (azure.com)
Validate the netFrameworkVersion:
Note: Refer the above blog for path to validation