error creating Application AutoScaling Target: ValidationException: Unsupported service namespace, resource type or scalable dimension - module

Question

I'm trying to enable ECS autoscaling for some Fargate services and run into the error in the title:
error creating Application AutoScaling Target: ValidationException: Unsupported service namespace, resource type or scalable dimension
The error happens on line 4 here:
resource "aws_appautoscaling_target" "autoscaling" {
max_capacity = var.max_capacity
min_capacity = 1
resource_id = var.resource_id
// <snip... a bunch of other vars not relevant to question>
I call the custom autoscaling module like so:
module "myservice_autoscaling" {
source = "../autoscaling"
resource_id = aws_ecs_service.myservice_worker.id
// <snip... a bunch of other vars not relevant to question>
My service is a normal ECS service block starting with:
resource "aws_ecs_service" "myservice_worker" {
After poking around online, I thought maybe I should construct the "service/clusterName/serviceName" sort of "manually", like so:
resource_id = "service/${var.cluster_name}/${aws_ecs_service.myservice_worker.name}"
But that leads to a different error:
The argument "cluster_name" is required, but no definition was found.
I created cluster_name in my calling module (i.e. myservice ECS stuff that calls my new autoscaling module) variables.tf. And I have cluster_name in the outputs.tf of our cluster module where we're setting up the ECS cluster. I must be missing some linking still.
Any ideas? Thanks!
Edit: here's the solution that got it working for me
Yes, you do need to construct the resource_id in the form of "service/yourClusterName/yourServiceName". Mine ended up looking like: "service/${var.cluster_name}/${aws_ecs_service.myservice_worker.name}"
You need to make sure you have access to the cluster name and service name variables. In my case, though I had the variable defined in my ECS service's variables.tf, and I added it my cluster module's outputs.tf, I was failing to pass down from the root module to the service module. This fixed that:
module "myservice" {
source = "./modules/myservice"
cluster_name = module.cluster.cluster_name // the line I added
(the preceding snippet goes in the main.tf of your root module (a level above your service module)

Answer 1

You are on the right track constructing the "service/${var.cluster_name}/${aws_ecs_service.myservice_worker.name}" string. It looks like you simply aren't referencing the cluster name correctly.
And I have cluster_name in the outputs.tf of our cluster module
So you need to reference that module output, instead of referencing a not-existent variable:
"service/${module.my_cluster_module.cluster_name}/${aws_ecs_service.myservice_worker.name}"
Change "my_cluster_module" to whatever name you gave the module that is creating your ECS cluster.