Null values handling in Terraform - Mini Project: Build & Apply

Null values handling

📖 Scenario: You are setting up a Terraform configuration to create cloud resources. Sometimes, certain optional values might not be provided, and you want to handle these null values safely to avoid errors.

🎯 Goal: Build a Terraform configuration that defines a variable which can be null, then use a default value when the variable is null to configure a resource properly.

📋 What You'll Learn

Create a variable called instance_type that can accept null values

Define a local variable final_instance_type that uses instance_type if it is not null, otherwise uses "t2.micro"

Create an AWS EC2 instance resource that uses final_instance_type as its instance type

Ensure the configuration is valid and deployable

💡 Why This Matters

🌍 Real World

Cloud infrastructure often requires optional configuration values. Handling null values safely prevents deployment errors and allows flexible configurations.

💼 Career

Knowing how to handle null values in Terraform is essential for cloud engineers and DevOps professionals to write robust infrastructure as code.

1

Define a variable that can be null

Create a Terraform variable called instance_type of type string that allows null values and has no default value.

Terraform

# Define the variable instance_type that can be null
# Your code here

Need a hint?

Use nullable = true to allow the variable to accept null values.

2

Create a local variable with a default fallback

Add a local variable called final_instance_type that uses the value of var.instance_type if it is not null, otherwise uses the string "t2.micro".

Terraform

variable "instance_type" {
  type = string
  nullable = true
}

# Define local.final_instance_type with fallback
# Your code here

Need a hint?

Use a conditional expression to check if var.instance_type is null.

3

Create an AWS EC2 instance resource using the local variable

Create a resource of type aws_instance named example that uses local.final_instance_type as the value for instance_type. Use ami = "ami-12345678" as a placeholder AMI ID.

Terraform

variable "instance_type" {
  type = string
  nullable = true
}

locals {
  final_instance_type = var.instance_type != null ? var.instance_type : "t2.micro"
}

# Create aws_instance resource using local.final_instance_type
# Your code here

Need a hint?

Use local.final_instance_type for the instance_type attribute.

4

Add provider configuration for AWS

Add a provider block for aws with region set to us-east-1 to complete the configuration.

Terraform

variable "instance_type" {
  type = string
  nullable = true
}

locals {
  final_instance_type = var.instance_type != null ? var.instance_type : "t2.micro"
}

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = local.final_instance_type
}

# Add AWS provider configuration
# Your code here

Need a hint?

The provider block is required to deploy AWS resources.