How to define global variables in terraform?

Question

I have a terraform project I am working on. In it, I want a file to contain many variables. I want these variables to be accessible from any module of the project. I have looked in the docs and on a Udemy course but still don't see how to do this. How does one do this in terraform?

Answer 1

I don't think this is possible. There are several discussions about this at Github, but this is not something the Hashicorp team wants.

In general we're against the particular solution of Global Variables, since it makes the input -> resources -> output flow of Modules less explicit, and explicitness is a core design goal.

I know, we have to repeat a lot of variables between different modules

Answer 2

For pathing constants between lots of modules we can use the following simple way.

/modules/global_constants/outputs.tf:

Describe module with global constants as outputs:

output "parameter_1" {
  value     = "value_1"
  sensitive = true
}

output "parameter_2" {
  value     = "value_2"
  sensitive = true
}

/example_1.tf

After we can use in any *.tf

module "global_settings" {
   source = "./modules/global_constants"
}

data "azurerm_key_vault" "keyvault" {
   name                = module.global_settings.parameter_1
   resource_group_name = module.global_settings.parameter_2
}

/modules/module2/main.tf

Or in other any modules:

module "global_settings" {
   source = "../global_constants"
}

data "azurerm_key_vault" "keyvault" {
   name                = module.global_settings.parameter_1
   resource_group_name = module.global_settings.parameter_2
}