5. Advanced on Terraform Basics on AWS Training

5.1. Modules

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Create a new directory for this exercise:

mkdir -p $LAB_ROOT/advanced/modules
cd $LAB_ROOT/advanced/modules

Optional: Create empty file:

touch main.tf

Step 5.1.1: Define the module

A local module resides in its own directory, lets create one be running:

mkdir random_file

Create a new file named random_file/variables.tf and add the following content:

variable "extension" {}
variable "size" {}

Create a new file named random_file/main.tf and add the following content:

resource "random_pet" "filename" { }

resource "random_password" "content" {
 length = var.size
}

resource "local_file" "this" {
 filename = "${random_pet.filename.id}.${var.extension}"
 content = random_password.content.result
}

Create a new file named random_file/outputs.tf and add the following content:

5.2. Meta-Arguments

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Create a new directory for this exercise:

mkdir -p $LAB_ROOT/advanced/meta_arguments
cd $LAB_ROOT/advanced/meta_arguments

Optional: Create empty files:

touch main.tf

Step 5.2.1: Missing dependency

Sometimes Terraform can not imply the dependency between resources explicitly. For such cases, a dependency is added to one or multiple resources or data sources. Consider the following snippets.

Create a new file named main.tf and add the following content:

resource "local_file" "foobar_txt" {
 content = "4thelulz"
 filename = "foobar.txt"
}

data "local_file" "reference" {
 filename = "foobar.txt"
}

Now run:

5.3. Various

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Create a new directory for this exercise:

mkdir $LAB_ROOT/advanced/various
cd $LAB_ROOT/advanced/various

Optional: Create empty files:

touch {main,variables,outputs}.tf

Step 5.3.1: Variable structure

Terraform variables support nested complex types like nested maps and sets. The type keyword of the variable block allows the definition of type constraints to enforce the correctness of the input (or default) value. See https://developer.hashicorp.com/terraform/language/expressions/type-constraints for the specification.

Create a new file named variables.tf and add the following content:

variable "clouds" {
 default = {
 aws = {
 company = "Amazon"
 founder = "Jeff Bezos"
 cloud_rank = 1
 }
 azure = {
 company = "Microsoft"
 founder = "Bill Gates"
 cloud_rank = 2
 }
 gcp = {
 company = "Google"
 founder = "Larry Page and Sergey Brin"
 cloud_rank = 3
 }
 }
 type = map(object({
 company = string
 founder = string
 cloud_rank = number
 }))
}

The code snippet above defines a map for the top three cloud platforms with three attributes:

5.4. Templates

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Create a new directory for this exercise:

mkdir $LAB_ROOT/advanced/templates
cd $LAB_ROOT/advanced/templates

Optional: Create empty files:

touch {main,variables,outputs}.tf

Step 5.4.1: Multiline strings

Sometimes you’d like to construct multiline strings while avoiding \n escape sequences for readability.
Terraform offers so called “heredoc” style string literals to achieve that. The full documentation can be found at https://www.terraform.io/docs/language/expressions/strings.html

Create a new file named variables.tf and add the following content:

variable "action" {
 default = "fun"
}

Create a new file named outputs.tf and add the following content: