Day 2: Mastering Terraform Variables - A Comprehensive Guide

Day 2: Mastering Terraform Variables - A Simplified Guide

Welcome back to our Terraform learning journey! Today, we'll unravel the power of Terraform variables. Let's dive right in and make our infrastructure more dynamic and flexible.

Recap of Day 1.1: Terraform and Docker Harmony

In our previous adventure, we witnessed the seamless integration of Docker into Terraform, orchestrating containers with precision. Now, armed with this knowledge, let's move forward to Day 2, where we'll delve into the realm of Terraform variables.

Understanding the Challenge

Imagine you've created a Terraform configuration to generate a local file named devops.txt. The catch? If you want to change the filename, you're tempted to modify the main.tf file directly. However, this goes against coding best practices. The solution? Harness the power of Terraform variables!

Introducing Terraform Variables

Variables in Terraform act as containers for values, allowing us to create dynamic and reusable infrastructure. But before we jump into the code, let's organize our project structure:

• main.tf: The main Terraform configuration file

  resource local_file "devops_var" {
    filename = "/study/terraform/Day2/devops.txt"
    content  = "this is Day2 of terraform"
  }
        

• variables.tf: The file to house all our variables.

Creating Variables

Let's start by creating a variables.tf file:

variables.tf

variable "filename" {

default = "/study/terraform/Day2/devops_variables.txt" 
} 

variable "content" { 
default = "this is autogenerated from Terraform variables" 
}        

In this file, we define two variables: filename and content. The default attribute initializes their values.

Using Variables in main.tf

Now, let's leverage these variables in our main.tf:

main.tf

resource "local_file" "devops_var" {

 filename = var.filename 
 content = var.content

 }        

In the resource block, we use the var. syntax to reference our variables. This separation allows us to modify configurations without directly changing the main.tf file.

Understanding the Difference

Now, let's run terraform init, terraform plan, and terraform apply. Our new local file, devops_variables.txt, will be created with the specified content.

Difference between Resources:

• Without Variables:

resource "local_file" "devops_var" {

 filename = "/study/terraform/Day2/devops.txt"

 content = "this is Day2 of Terraform" 
}        

• With Variables:

resource "local_file" "devops_var" {

 filename = var.filename 

content = var.content

 }        

By utilizing variables, we've made our configuration more adaptable without directly modifying the main.tf file.

Primitive Variable Types

String:

Strings in Terraform are your go-to choice for handling any text-based values. Whether it's a region, a username, or a simple label, strings have you covered. Here's a quick dive into using strings:

variable "aws_region" {

  type    = string

  default = "ap-south-1"

}        

In this example, aws_region is a string variable holding the AWS region "us-west-2". You can customize it with any text-based value fitting your infrastructure needs.

Number:

Numbers, as the name suggests, deal with numeric values, both integers and floating-point numbers. They're handy when specifying quantities or numerical configurations. Let's jump into an illustration:

variable "instance_count" {

  type    = number

  default = 4

}        

Here, instance_count is a number variable set to the default value of 3. It could represent the number of instances you want to deploy. Terraform handles it as a numerical entity, allowing for precise quantity definitions.

Bool:

The Bool type is capable of holding either true or false values. For example, if we define the logging variables as a type of bool with a value defaulting to true, the logging function will be enabled. You can change the default value from true to false to disable it.

variable "logging" { 
type = bool 
default = true
 }        

Exploring Complex Data Types

Terraform supports various complex data types. Let's briefly touch on a few:

Map:

variable "content_map" { 

type = map 

default = {

content1 = "this is cool content1" 

content2 = "this is great content"
 }
 }        

List:

List variables are used to sequentially pass multiple elements to Terraform configuration

variable "file_list" { 

type = list

 default = ["/study/terraform/Day2/file_1.txt", "/study/terraform/Day2/file_2.txt"] }        

Object:

The object variable allows you to create variables that contain structured data and named attributes. This is similar to a map but has fixed names and types for the attributes.

variable "aws_ec2_object" { 

type = object({
 name = string 
instances = number 
keys = list(string)
 ami = string }) 

default = { 
name = "test_ec2_instances"
instances = 2 
keys = ["keys1.pem", "keys2.pem"]
 ami = "ami-11664" 
} }        

• Set, A set in Terraform is like a magical bag where uniqueness reigns, and order doesn't matter. This makes sets perfect for scenarios where you want to ensure uniqueness within a collection of values. Let's dive into an example

variable "security_groups" {
  type    = set(string)
  default = ["sg-12345678", "sg-abcdefgh"]
}
        

Tuple:

Unlike sets, tuples in Terraform maintain order. They are an ordered collection of elements, making them handy when sequence matters. Let's explore a tuple in action:

variable "IP_addresses" {
  type    = tuple([string, string])
  default = ["192.168.20.10", "192.168.10.22"]
}
        

Conclusion

In this immersive exploration of Terraform variables, you've delved into the intricacies of complex data types and harnessed the power of dynamic configurations. By adopting the best practice of segregating variables into a dedicated file, you've laid a robust foundation for your Terraform projects.

Stay tuned for more thrilling Terraform adventures as we continue to unravel its capabilities and make infrastructure as code an exhilarating journey. Happy coding, and may your Terraform endeavors be nothing short of magical! ???? #TerraformMagic #InfrastructureAsCode #Day2 #VariablesUnleashed