Terragrunt for DRY configurations in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Terragrunt's Purpose

What is the main benefit of using Terragrunt with Terraform?

A It helps avoid repeating the same Terraform code by managing configurations centrally.

B It automatically scales cloud resources based on traffic.

C It replaces Terraform and runs cloud infrastructure without code.

D It provides a graphical interface to design cloud infrastructure visually.

💡 Hint

Think about how Terragrunt helps when you have many similar infrastructure setups.

Terragrunt is a tool that helps keep Terraform configurations DRY (Don't Repeat Yourself) by allowing you to reuse and manage common settings in one place.

❓ Configuration

intermediate

Terragrunt Configuration Inheritance

Given a Terragrunt configuration file terragrunt.hcl that includes a remote_state block, which option correctly shows how to inherit this remote state configuration in a child module?

Terraform

remote_state {
  backend = "s3"
  config = {
    bucket = "my-terraform-state"
    key    = "global/terraform.tfstate"
    region = "us-east-1"
  }
}

A

include {
  path = find_in_parent_folders()
}

remote_state = include.get().remote_state

B

include {
  path = find_in_parent_folders()
}

remote_state {
  backend = "s3"
  config = {
    bucket = "my-terraform-state"
    key    = "global/terraform.tfstate"
    region = "us-east-1"
  }
}

C

include {
  path = find_in_parent_folders()
}

remote_state = local.remote_state

D

remote_state {
  backend = "s3"
  config = {
    bucket = "my-terraform-state"
    key    = "global/terraform.tfstate"
    region = "us-east-1"
  }
}

💡 Hint

Look for the syntax that references the parent's remote_state block after including it.

In Terragrunt, after including a parent configuration with include, you can access its blocks using include.get(). This allows child modules to inherit settings like remote_state without redefining them.

❓ Architecture

advanced

Terragrunt Folder Structure for Multiple Environments

You want to manage Terraform infrastructure for two environments: dev and prod. Using Terragrunt, which folder structure best supports DRY principles and environment isolation?

A

/terraform/
  /dev/
    main.tf
  /prod/
    main.tf
  terragrunt.hcl

B

/modules/
  /dev/
    main.tf
  /prod/
    main.tf

C

/live/
  /dev/
    terragrunt.hcl
  /prod/
    terragrunt.hcl
  terragrunt.hcl

D

/live/
  /dev/
    main.tf
  /prod/
    main.tf

💡 Hint

Think about where Terragrunt files should be placed to share common configs and separate environments.

Terragrunt encourages a folder structure where a root terragrunt.hcl holds shared configs, and environment folders have their own terragrunt.hcl files to override or add environment-specific settings. This keeps code DRY and environments isolated.

❓ security

advanced

Securing Sensitive Variables in Terragrunt

Which approach best protects sensitive variables like passwords when using Terragrunt with Terraform?

A Store sensitive variables directly in <code>terragrunt.hcl</code> files in plain text.

B Use environment variables or encrypted secrets managers and reference them in Terragrunt configs.

C Commit sensitive variables in Terraform <code>.tf</code> files to version control for easy access.

D Hardcode sensitive values in Terraform modules to avoid passing them through Terragrunt.

💡 Hint

Think about how to keep secrets safe and avoid exposing them in code repositories.

Best practice is to avoid storing sensitive data in code files. Instead, use environment variables or secret management tools and reference those securely in Terragrunt configurations.

❓ service_behavior

expert

Terragrunt Behavior with Dependency Blocks

Consider this Terragrunt configuration snippet:

dependency "vpc" {
  config_path = "../vpc"
}

inputs = {
  vpc_id = dependency.vpc.outputs.vpc_id
}

What happens if the ../vpc module has not been applied yet when you run Terragrunt in this module?

A Terragrunt ignores the dependency and applies the current module without the <code>vpc_id</code> input.

B Terragrunt fails with an error because the dependency outputs are missing.

C Terragrunt prompts the user to manually apply the dependency module before continuing.

D Terragrunt automatically applies the <code>../vpc</code> module first, then uses its outputs.

💡 Hint

Think about how Terragrunt manages dependencies between modules automatically.

Terragrunt automatically applies dependency modules first to ensure their outputs are available for the current module. This helps manage complex infrastructure with dependencies smoothly.

Practice

1. What is the main purpose of using Terragrunt with Terraform?

easy

A. To reuse Terraform configurations and avoid repeating code

B. To replace Terraform with a new tool

C. To write Terraform code in a different programming language

D. To deploy applications without infrastructure

Solution

1. Step 1: Understand Terragrunt's role

   Terragrunt is designed to help reuse and share Terraform code, making it easier to manage infrastructure without repeating code.

2. Step 2: Compare options

   Options B, C, and D describe incorrect uses or misunderstandings of Terragrunt's purpose.

3. Final Answer:

   To reuse Terraform configurations and avoid repeating code -> Option A

4. Quick Check:

   Terragrunt = DRY Terraform code reuse [OK]

Hint: Terragrunt helps avoid repeating Terraform code [OK]

Common Mistakes:

• Thinking Terragrunt replaces Terraform
• Believing Terragrunt changes Terraform language
• Confusing Terragrunt with application deployment tools

2. Which of the following is the correct way to include a Terraform module using Terragrunt?

easy

A. module "app" { source = "./app" }

B. include { path = find_in_parent_folders() }

C. terraform { backend = "s3" }

D. resource "aws_instance" "web" {}

Solution

1. Step 1: Identify Terragrunt syntax for including configs

   Terragrunt uses the include block with path = find_in_parent_folders() to reuse parent configs.

2. Step 2: Differentiate from Terraform syntax

   Options A, C, and D are Terraform syntax: A is a module block, C is backend config, D is a resource block, not Terragrunt includes.

3. Final Answer:

   include { path = find_in_parent_folders() } -> Option B

4. Quick Check:

   Terragrunt include uses find_in_parent_folders() [OK]

Hint: Terragrunt includes parent config with include + find_in_parent_folders() [OK]

Common Mistakes:

• Using Terraform module syntax instead of Terragrunt include
• Confusing backend config with include
• Writing resource blocks inside Terragrunt files

3. Given this Terragrunt configuration snippet:

include {
  path = find_in_parent_folders()
}

inputs = {
  region = "us-east-1"
  env    = "prod"
}

What will happen when you run terragrunt apply in this folder?

medium

A. Terragrunt will apply Terraform code without any variables

B. Terragrunt will fail because inputs cannot be used with include

C. Terragrunt will ignore the inputs block and only use parent config

D. Terragrunt will apply Terraform code using the parent config and inputs region=us-east-1, env=prod

Solution

1. Step 1: Understand include and inputs usage

   The include block imports parent config. The inputs block adds or overrides variables for this folder.

2. Step 2: Predict Terragrunt behavior on apply

   Terragrunt merges parent config with local inputs, so region and env variables are set as given.

3. Final Answer:

   Terragrunt will apply Terraform code using the parent config and inputs region=us-east-1, env=prod -> Option D

4. Quick Check:

   Include + inputs = merged config applied [OK]

Hint: Inputs override or add variables when using include [OK]

Common Mistakes:

• Thinking inputs are ignored with include
• Assuming inputs cause errors
• Believing variables are not passed to Terraform

4. You wrote this Terragrunt config:

include {
  path = find_in_parent_folders()
}

inputs = {
  region = "us-west-2"
  env = "dev"
}

terraform {
  source = "../modules/app"
}

When running terragrunt apply, you get an error: "Error: Unsupported block type". What is the likely cause?

medium

A. The terraform block cannot be nested inside the inputs block

B. The inputs block must come before include

C. The source path is incorrect

D. The region variable is invalid

Solution

1. Step 1: Check Terragrunt config block usage

   Terragrunt requires the terraform { source = ... } block at the root level. It cannot be nested inside other blocks like inputs.

2. Step 2: Identify error cause

   The error "Unsupported block type" usually means the block is misplaced or invalid in Terragrunt config.

3. Final Answer:

   The terraform block cannot be nested inside the inputs block -> Option A

4. Quick Check:

   Misplaced terraform block causes error [OK]

Hint: Terraform block must be correctly placed in Terragrunt config [OK]

Common Mistakes:

• Placing terraform block inside inputs or include
• Wrong order of blocks causing syntax errors
• Incorrect source path causing unrelated errors

5. You manage multiple environments (dev, staging, prod) with Terragrunt. You want to avoid repeating the backend configuration for each environment. Which approach best follows DRY principles?

hard

A. Define backend only in Terraform modules, not in Terragrunt

B. Copy the backend block into each environment's Terragrunt config

C. Create a root Terragrunt config with backend settings and use include in each environment folder

D. Use different backend types for each environment

Solution

1. Step 1: Understand DRY with Terragrunt

   Terragrunt allows sharing common config via a root config and include blocks in child folders.

2. Step 2: Evaluate options for backend reuse

   Create a root Terragrunt config with backend settings and use include in each environment folder uses root config for backend, avoiding repetition. Copy the backend block into each environment's Terragrunt config repeats code, violating DRY. Define backend only in Terraform modules, not in Terragrunt is incorrect because backend is configured in Terragrunt for remote state. Use different backend types for each environment adds complexity without reuse.

3. Final Answer:

   Create a root Terragrunt config with backend settings and use include in each environment folder -> Option C

4. Quick Check:

   Root config + include = DRY backend config [OK]

Hint: Put shared backend in root config, include it in environments [OK]

Common Mistakes:

• Copying backend config to each environment
• Configuring backend only in Terraform modules
• Using different backends unnecessarily