Review Project

Let’s explore the generated app folder.

App Modules

Let’s check out the app/modules/example folder.

main.tf

resource "random_pet" "this" {
  length = var.length
}

variables.tf

variable "length" {
  type        = number
  description = "number of words"
  default     = 2
}

You can see that the starter example module creates a random_pet resource.

Next let’s look at the generated app/stacks/demo that was created:

app/stacks/demo/main.tf

module "pet" {
  source     = "../../modules/example"
  length     = var.length
}

You can see that it’s just another terraform module, that will use the app/modules/example module to create the random_pet.

Both modules and stacks are terraform modules. The difference is organizational and how they are can be used.

Modules are reusable pieces of code. Generally, it contains non-business specific logic.
Stacks can be used to group together modules. Generally, this is where more business-specific logic can go.

For example, the app1 stack could be designed to use a server module. Another, app2 stack could use a server and a database modules.

There are no hard rules. Stacks can be reusable and you provide the tfvars config. It’s up to you. Here are some more Tfvars Location Thoughts.

Next, we’ll deploy the infrastructure.