Why modules enable reusability in Terraform - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a module block in Terraform.

Terraform

module "example" {
  source = [1]
}

Drag options to blanks, or click blank then click option'

A"variable"

B"aws_instance"

C"./modules/example"

D"terraform"

Attempts:

3 left

💡 Hint

Common Mistakes

Using resource type names instead of a path for source.

Leaving source empty or with invalid strings.

The source attribute specifies the path to the module folder, enabling reuse of that module.

2fill in blank

medium

Complete the code to pass a variable to a module.

Terraform

module "example" {
  source = "./modules/example"
  instance_type = [1]
}

Drag options to blanks, or click blank then click option'

A"variable"

B"t2.micro"

Ct2.micro

Dinstance_type

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting quotes around string values.

Using variable names without quotes as values.

Module input variables are assigned values using key = value pairs. The value must be a string if the variable expects a string.

3fill in blank

hard

Fix the error in the module output block.

Terraform

output "instance_id" {
  value = module.example.[1]
}

Drag options to blanks, or click blank then click option'

Ainstance_id

Binstance

Cid

Doutput_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using resource attribute names instead of output names.

Using incorrect or partial output names.

The output value references the module's output variable name, which is instance_id in this case.

4fill in blank

hard

Fill both blanks to define a reusable module with variables and outputs.

Terraform

variable "[1]" {
  type = string
}

output "[2]" {
  value = var.[1]
}

Drag options to blanks, or click blank then click option'

Ainstance_type

Binstance_id

Dinstance_name

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing variable and output names.

Using the same name for both variable and output.

The variable name is instance_type, and the output returns a value named instance_id which could be set elsewhere in the module.

5fill in blank

hard

Fill all three blanks to call a module with variables and use its output.

Terraform

module "web" {
  source = [1]
  instance_type = [2]
}

output "web_id" {
  value = module.web.[3]
}

Drag options to blanks, or click blank then click option'

A"./modules/webserver"

B"t3.small"

Cinstance_id

D"aws_instance"

Attempts:

3 left

💡 Hint

Common Mistakes

Using resource types instead of paths for source.

Omitting quotes around string values.

Referencing wrong output names.

The module source is a local path, the instance type is a string, and the output references the module's output variable instance_id.

Practice

1. What is the main benefit of using modules in Terraform?

easy

A. They let you reuse code to save time and reduce errors

B. They increase the cost of cloud resources

C. They make Terraform run slower

D. They prevent you from customizing infrastructure

Solution

1. Step 1: Understand what modules do

   Modules are reusable pieces of Terraform code that you can use multiple times.

2. Step 2: Identify the main benefit

   Using modules saves time and reduces errors by avoiding repeated code.

3. Final Answer:

   They let you reuse code to save time and reduce errors -> Option A

4. Quick Check:

   Modules = Reusability and error reduction [OK]

Hint: Modules = reusable code blocks to save time [OK]

Common Mistakes:

• Thinking modules increase costs
• Believing modules slow down Terraform
• Assuming modules prevent customization

2. Which syntax correctly calls a module named network in Terraform?

easy

A. resource "module" "network" { source = "./network" }

B. module "network" { source = "./network" }

C. module network { source = ./network }

D. resource "network" { source = "./network" }

Solution

1. Step 1: Recall module block syntax

   Modules are called using the module "name" { ... } block syntax.

2. Step 2: Check the correct usage

   module "network" { source = "./network" } uses the correct syntax with quotes around the module name and source path.

3. Final Answer:

   module "network" { source = "./network" } -> Option B

4. Quick Check:

   Module call syntax = module "name" [OK]

Hint: Module calls use module "name" { source = ... } [OK]

Common Mistakes:

• Using resource instead of module
• Omitting quotes around source path
• Mixing resource and module keywords

3. Given this module call:

module "web" {
  source = "./webserver"
  instance_count = 3
}

What happens when you change instance_count in the module input?

medium

A. Terraform deletes the module entirely

B. Terraform ignores the change and keeps the old count

C. Terraform creates or destroys instances to match the new count

D. Terraform throws a syntax error

Solution

1. Step 1: Understand module inputs

   Module inputs customize resources inside the module, like instance count.

2. Step 2: Effect of changing input

   Changing instance_count causes Terraform to update resources to match the new number.

3. Final Answer:

   Terraform creates or destroys instances to match the new count -> Option C

4. Quick Check:

   Module inputs control resource changes [OK]

Hint: Changing inputs updates resources accordingly [OK]

Common Mistakes:

• Thinking Terraform ignores input changes
• Assuming module is deleted on input change
• Expecting syntax errors from input changes

4. You wrote this module call:

module "db" {
  source = "./database"
  size = 10
  size = 20
}

What error will Terraform show?

medium

A. Duplicate argument 'size' declared

B. Missing required argument 'size'

C. Invalid source path error

D. No error, uses last 'size' value

Solution

1. Step 1: Check for duplicate arguments

   The module call has two size arguments, which is not allowed.

2. Step 2: Terraform error on duplicates

   Terraform throws an error about duplicate argument names in the same block.

3. Final Answer:

   Duplicate argument 'size' declared -> Option A

4. Quick Check:

   Duplicate args cause errors [OK]

Hint: No duplicate keys allowed in module blocks [OK]

Common Mistakes:

• Assuming last value overrides silently
• Ignoring duplicate argument errors
• Confusing missing argument with duplicates

5. You want to reuse a module for different environments (dev, prod) with different settings. What is the best way to achieve this?

hard

A. Copy the module code into separate folders for each environment

B. Create a new Terraform project for each environment without modules

C. Use one module call and manually edit the code each time

D. Call the module multiple times with different input variables for each environment

Solution

1. Step 1: Understand module reusability

   Modules are designed to be called multiple times with different inputs to customize behavior.

2. Step 2: Best practice for environments

   Calling the same module with different variables for dev and prod avoids code duplication and errors.

3. Final Answer:

   Call the module multiple times with different input variables for each environment -> Option D

4. Quick Check:

   Reuse modules with inputs for different environments [OK]

Hint: Use inputs to customize module calls per environment [OK]

Common Mistakes:

• Copying module code instead of reusing
• Editing module code manually each time
• Avoiding modules for environment separation