The World of Terraform

Terraform is like our personal architect for the cloud. It helps us build and manage our digital kingdom, be it servers, databases, or any other tech marvel. To work its magic, Terraform uses something called "Variable Interpolation," which is like pieces of information it needs to make things happen.

Variable Interpolation

Variable Interpolation is the process of inserting the value of the variable into a terraform configuration. This can be used to make our Terraform more dynamic and flexible.

Defining the variables in the same main.tf

Terraform variables are like labelled containers that hold vital information for our infrastructure. Let's define a few variables in the same configuration file to create a simple AWS instance:

# main.tf

variable "instance_count" {
  description = "The number of AWS instances to create."
  type        = number
  default     = 2
}

variable "instance_type" {
  description = "The type of AWS instance to create."
  type        = string
  default     = "t2.micro"
}

variable "ami_id" {
  description = "The ID of the AWS AMI to use."
  type        = string
  default     = "ami-0c55b159cbfafe1f0"
}

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "my_server" {
  count         = var.instance_count
  instance_type = var.instance_type
  ami           = var.ami_id
}

output "server_public_ip" {
  value = aws_instance.my_server[*].public_ip
}

In this section, we define variables directly within "main.tf" and use them to create an AWS instance, while also specifying a default value for each variable.

Defining the variables by creating variables.tf

To separate our variables into a dedicated file, create a new file named variables.tf. This helps keep our code organized and makes it easier to manage our variables independently.

# variables.tf

variable "instance_count" {
  description = "The number of AWS instances to create."
  type        = number
  default     = 2
}

variable "instance_type" {
  description = "The type of AWS instance to create."
  type        = string
  default     = "t2.micro"
}

variable "ami_id" {
  description = "The ID of the AWS AMI to use."
  type        = string
  default     = "ami-0c55b159cbfafe1f0"
}

After creating the "variables.tf", we can use it in our "main.tf" file.

In our main.tf, we can reference these variables using the var keyword:

# main.tf

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "my_server" {
  count         = var.instance_count
  instance_type = var.instance_type
  ami           = var.ami_id
}

output "server_public_ip" {
  value = aws_instance.my_server[*].public_ip
}

By using var.instance_count, var.instance_type, and var.ami_id, we can tell Terraform to use the values from your variables when creating resources.

Running Terraform Commands

To apply these configurations, save the main.tf and variables.tf files in the same directory. Ensure Terraform is installed, and then run the following commands:

1. terraform init - Initialize your Terraform project.

2. terraform plan - Preview the changes Terraform will make.

3. terraform apply - Apply the configurations to create the AWS instance.

With these steps, we'll have harnessed the magic of Terraform's variable interpolation to conjure our digital infrastructure.

Conclusion

Terraform variable interpolation is the key to building flexible and scalable infrastructure. We can define variables in the same configuration file or separate them into a variable.tf for a more organized structure. This approach allows for easy management and dynamic updates to our infrastructure code as our project evolves