Terraform referenced module has no attributes error - google-cloud-platform

Question

I am trying to use a Palo Alto Networks module to deploy a panorama VM instance to GCP with Terraform. In the example module, I see they create a VPC together with a subnetwork, however, I have an existing VPC I am adding to. So I data source the VPC and create the subnetwork with a module. Upon referencing this subnetwork in my VM instance module, it complains it has no attributes:
Error: Incorrect attribute value type
on ../../../../modules/panorama/main.tf line 67, in resource "google_compute_instance" "panorama":
67: subnetwork = var.subnet
|----------------
| var.subnet is object with no attributes
Here is the subnet code:
data "google_compute_network" "panorama" {
project = var.project_id
name = "fed-il4-p-net-panorama"
}
module "panorama_subnet" {
source = "../../../../modules/subnetwork-module"
subnet_name = "panorama-${var.region_short_name[var.region]}"
subnet_ip = var.panorama_subnet
subnet_region = var.region
project_id = var.project_id
network = data.google_compute_network.panorama.self_link
}
Here is the panorama VM instance code:
module "panorama" {
source = "../../../../modules/panorama"
name = "${var.project_id}-panorama-${var.region_short_name[var.region]}"
project = var.project_id
region = var.region
zone = data.google_compute_zones.zones.names[0]
*# panorama_version = var.panorama_version
ssh_keys = (file(var.ssh_keys))
network = data.google_compute_network.panorama.self_link
subnet = module.panorama <====== I cannot do module.panorama.id or .name here
private_static_ip = var.private_static_ip
custom_image = var.custom_image_pano
#attach_public_ip = var.attach_public_ip
}
Can anyone tell me what I may be doing wrong. Any help would be appreciated. Thanks!
Edit:
parent module for vm instance
resource "google_compute_instance" "panorama" {
name = var.name
zone = var.zone
machine_type = var.machine_type
min_cpu_platform = var.min_cpu_platform
labels = var.labels
tags = var.tags
project = var.project
can_ip_forward = false
allow_stopping_for_update = true
metadata = merge({
serial-port-enable = true
ssh-keys = var.ssh_keys
}, var.metadata)
network_interface {
/*
dynamic "access_config" {
for_each = var.attach_public_ip ? [""] : []
content {
nat_ip = google_compute_address.public[0].address
}
}
*/
network_ip = google_compute_address.private.address
network = var.network
subnetwork = var.subnet
}

Answer 1

I've come across this issue var.xxx is object with [n] attributes multiple times, and 9/10 times it has got to do with wrong referencing of a variable. In your case, in the panorama VM module , you're assigning value of subnet as:
subnet = module.panorama
Now, its not possible to assign a module to an attribute within the module. From your problem statement, i see you're trying to get name attribute assigned to subnet. Try this:
subnet = this.id OR
subnet = this.name
Also, regarding what values can be called, the resources defined in a module are encapsulated, so the calling module cannot access their attributes directly. However, the child module can declare output values to selectively export certain values to be accessed by the calling module.
For example, if the ./panorama module referenced in the example below exported an output value named subnet
module "panorama" {
source = "../../../../modules/panorama"
output "subnet_name" {
value = var.subnet
}
OR WITHOUT SETTING subnet VALUE
output "subnet_name" {
value = var.name
}
then the calling module can reference that result using the expression module.panorama.outputs.subnet_name. Hope this helps