Variable validation rules in Terraform - Mini Project: Build & Apply

Terraform Variable Validation Rules

📖 Scenario: You are setting up a Terraform configuration to deploy cloud resources. To avoid mistakes, you want to add rules that check if the input variables meet certain conditions before applying the configuration.

🎯 Goal: Create a Terraform variable with validation rules that ensure the input is a string with a length between 3 and 10 characters.

📋 What You'll Learn

Define a variable named environment of type string

Add a validation block that checks the length of environment is at least 3 characters

Add a validation block that checks the length of environment is at most 10 characters

Provide a custom error message if the validation fails

💡 Why This Matters

🌍 Real World

Terraform variable validation helps prevent mistakes by checking user inputs before deploying cloud infrastructure, saving time and avoiding errors.

💼 Career

Cloud engineers and DevOps professionals use variable validation to create reliable and user-friendly Terraform modules and configurations.

1

Create the environment variable

Create a Terraform variable named environment of type string.

Terraform

# Your code here

Need a hint?

Use the variable block with the name environment and set type = string.

2

Add minimum length validation

Add a validation block inside the environment variable that checks if the length of var.environment is at least 3 characters using length(var.environment) >= 3.

Terraform

variable "environment" {
  type = string
  # Your code here
}

Need a hint?

Use a validation block with condition and error_message inside the variable.

3

Add maximum length validation

Add another validation block inside the environment variable that checks if the length of var.environment is at most 10 characters using length(var.environment) <= 10. Keep the previous validation block as well.

Terraform

variable "environment" {
  type = string
  validation {
    condition     = length(var.environment) >= 3
    error_message = "The environment name must be at least 3 characters long."
  }
  # Your code here
}

Need a hint?

Add a second validation block with the maximum length condition and error message.

4

Complete the variable with both validations

Ensure the environment variable block includes both validation blocks for minimum and maximum length with their respective error messages.

Terraform

variable "environment" {
  type = string
  validation {
    condition     = length(var.environment) >= 3
    error_message = "The environment name must be at least 3 characters long."
  }
  validation {
    condition     = length(var.environment) <= 10
    error_message = "The environment name must be at most 10 characters long."
  }
  # Your code here
}

Need a hint?

Review the entire variable block to confirm both validations are present.