How do I fully deploy Containerized Azure Function App with Terraform - azure

Question

Attempting to deploy a Function App on a Premium plan that serves the functions from a container. The HOWTO for this works well enough: https://learn.microsoft.com/en-us/azure/azure-functions/functions-create-function-linux-custom-image?tabs=nodejs#create-an-app-from-the-image
However, when I try to deploy it using Terraform, no sale. Everything looks right but the function does not show up in the side menu (it does for the one deployed with the az CLI), nor can I hit it with Postman.
Via Resource Explorer I can see that the Functions are not being populated. Here is the HCL that I am using
resource "azurerm_app_service_plan" "plan" {
name = "${var.app_name}-Premium-ConsumptionPlan"
location = "WestUS"
resource_group_name = "${data.azurerm_resource_group.rg.name}"
kind = "Elastic"
reserved = true
sku {
tier = "ElasticPremium"
size = "EP1"
}
}
data "azurerm_container_registry" "registry" {
name = "${var.app_name}registry"
resource_group_name = "${data.azurerm_resource_group.rg.name}"
}
resource "azurerm_function_app" "funcApp" {
name = "${var.app_name}-userapi-${var.env_name}-funcapp"
location = "WestUS"
resource_group_name = "${data.azurerm_resource_group.rg.name}"
app_service_plan_id = "${azurerm_app_service_plan.plan.id}"
storage_connection_string = "${azurerm_storage_account.storage.primary_connection_string}"
version = "~2"
app_settings = {
FUNCTIONS_EXTENSION_VERSION = "~2"
FUNCTIONS_WORKER_RUNTIME = "dotnet"
DOCKER_REGISTRY_SERVER_URL = "${data.azurerm_container_registry.registry.login_server}"
DOCKER_REGISTRY_SERVER_USERNAME = "${data.azurerm_container_registry.registry.admin_username}"
DOCKER_REGISTRY_SERVER_PASSWORD = "${data.azurerm_container_registry.registry.admin_password}"
WEBSITE_CONTENTAZUREFILECONNECTIONSTRING = "${azurerm_storage_account.storage.primary_connection_string}"
DOCKER_CUSTOM_IMAGE_NAME = "${data.azurerm_container_registry.registry.login_server}/pingtrigger:test"
WEBSITE_CONTENTSHARE = "${azurerm_storage_account.storage.name}"
FUNCTION_APP_EDIT_MODE = "readOnly"
}
site_config {
always_on = true
linux_fx_version = "DOCKER|${data.azurerm_container_registry.registry.login_server}/pingtrigger:test"
}
}
----- Updated based on answer ----
The solution was to instruct Function App to NOT use storage to discover metadata about available functions - this involves setting WEBSITES_ENABLE_APP_SERVICE_STORAGE to false. Here is my updated script
resource "azurerm_app_service_plan" "plan" {
name = "${var.app_name}-premiumPlan"
resource_group_name = "${data.azurerm_resource_group.rg.name}"
location = "${data.azurerm_resource_group.rg.location}"
kind = "Linux"
reserved = true
sku {
tier = "Premium"
size = "P1V2"
}
}
data "azurerm_container_registry" "registry" {
name = "${var.app_name}registry"
resource_group_name = "${data.azurerm_resource_group.rg.name}"
}
resource "azurerm_function_app" "funcApp" {
name = "userapi-${var.app_name}fa-${var.env_name}"
location = "${data.azurerm_resource_group.rg.location}"
resource_group_name = "${data.azurerm_resource_group.rg.name}"
app_service_plan_id = "${azurerm_app_service_plan.plan.id}"
storage_connection_string = "${azurerm_storage_account.storage.primary_connection_string}"
version = "~2"
app_settings = {
FUNCTION_APP_EDIT_MODE = "readOnly"
https_only = true
DOCKER_REGISTRY_SERVER_URL = "${data.azurerm_container_registry.registry.login_server}"
DOCKER_REGISTRY_SERVER_USERNAME = "${data.azurerm_container_registry.registry.admin_username}"
DOCKER_REGISTRY_SERVER_PASSWORD = "${data.azurerm_container_registry.registry.admin_password}"
WEBSITES_ENABLE_APP_SERVICE_STORAGE = false
}
site_config {
always_on = true
linux_fx_version = "DOCKER|${data.azurerm_container_registry.registry.login_server}/testimage:v1.0.1"
}
}

Answer 1

To create the Azure Function with your custom Docker image, I think your problem is that you set the environment variable FUNCTIONS_WORKER_RUNTIME, it means you use the built-in runtime, but you want to use your custom image. With my test, you only need to configure the function app like this:
resource "azurerm_function_app" "funcApp" {
name = "${var.app_name}-userapi-${var.env_name}-funcapp"
location = "${azurerm_resource_group.main.location}"
resource_group_name = "${azurerm_resource_group.main.name}"
app_service_plan_id = "${azurerm_app_service_plan.plan.id}"
storage_connection_string = "${azurerm_storage_account.storage.primary_connection_string}"
version = "~2"
app_settings = {
FUNCTIONS_EXTENSION_VERSION = "~2"
DOCKER_REGISTRY_SERVER_URL = "${data.azurerm_container_registry.registry.login_server}"
DOCKER_REGISTRY_SERVER_USERNAME = "${data.azurerm_container_registry.registry.admin_username}"
DOCKER_REGISTRY_SERVER_PASSWORD = "${data.azurerm_container_registry.registry.admin_password}"
WEBSITE_CONTENTAZUREFILECONNECTIONSTRING = "${azurerm_storage_account.storage.primary_connection_string}"
WEBSITE_CONTENTSHARE = "${azurerm_storage_account.storage.name}"
DOCKER_CUSTOM_IMAGE_NAME = "${data.azurerm_container_registry.registry.login_server}/pingtrigger:test"
}
site_config {
always_on = true
linux_fx_version = "DOCKER|${data.azurerm_container_registry.registry.login_server}/pingtrigger:test"
}
}
Then you only need to wait a while for the creation.