Conditional flow within the different blocks in resource blocks of terraform - google-cloud-platform

Question

I'm trying to create a terraform script which takes user input and executes accordingly. I basically want to ask if the user wants static IP in Google cloud platform, if yes, then stitch the resource "google_compute_instance" accordingly, otherwise, let it go.
Sharing the code I have written:
variable "create_eip" {
description = "Enter 1 for true, 0 for false"
}
resource "google_compute_address" "external" {
count = "${var.create_eip}"
name = "external-ip",
address_type = "EXTERNAL",
}
resource "google_compute_instance" "compute-engine" {
name = "random",
machine_type = "f1-micro",
boot_disk {
initialize_params {
size = "10",
type = "pd-ssd",
image = "${data.google_compute_image.image.self_link}"
}
}
network_interface {
subnetwork = "default",
access_config {
nat_ip = "${google_compute_address.external.address}"
}
}
}
The error I'm getting here is when the user puts 0 as input the code control still goes to "nat_ip = "${google_compute_address.external.address}""
because of which I get this error:
google_compute_instance.compute-engine: Resource 'google_compute_address.external' not found for variable
'google_compute_address.external.address'.
I also tried it this way by replacing
nat_ip = "${var.create_eip == "1" ? "${google_compute_address.external.address}" : ""}"
(if create_ip = 1, execute "google_compute_address.external.address", else do nothing).
But it is not working as expected.

Answer 1

That's an issue with terraform...
You can't really do an if for something other than the count.
You could try something like that as you can't put condition inside a resource for now:
variable "create_eip" {
description = "Enter 1 for true, 0 for false"
}
resource "google_compute_address" "external" {
count = "${var.create_eip}"
name = "external-ip",
address_type = "EXTERNAL",
}
resource "google_compute_instance" "compute-engine-ip" {
count = "${var.create_eip == 1 ? 1 : 0}"
name = "random",
machine_type = "f1-micro",
boot_disk {
initialize_params {
size = "10",
type = "pd-ssd",
image = "${data.google_compute_image.image.self_link}"
}
}
network_interface {
subnetwork = "default",
access_config {
nat_ip = "${google_compute_address.external.address}"
}
}
}
resource "google_compute_instance" "compute-engine" {
count = "${var.create_eip == 1 ? 0 : 1}"
name = "random",
machine_type = "f1-micro",
boot_disk {
initialize_params {
size = "10",
type = "pd-ssd",
image = "${data.google_compute_image.image.self_link}"
}
}
network_interface {
subnetwork = "default",
access_config {
}
}
}
This code will create a compute instance using the created ip if the variable value is at one, in the other case it will create an ip, you could also add a lifecycle if you want to keep the same ip on the compute_address resource:
lifecycle = {
ignore_changes = ["node_pool"]
}