Module outputs in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Understanding Terraform module output usage

Given a Terraform root module that calls a child module which defines an output named instance_ip, what will be the value of module.webserver.instance_ip after applying the configuration?

Terraform

module "webserver" {
  source = "./modules/aws_instance"
  instance_count = 1
}

output "webserver_ip" {
  value = module.webserver.instance_ip
}

A The public IP address of the AWS instance created by the child module.

B The private IP address of the AWS instance created by the child module.

C An error because <code>instance_ip</code> is not defined in the root module.

D Null because outputs cannot be accessed from modules.

💡 Hint

Remember that outputs defined in child modules can be accessed via module.. in the root module.

The child module defines an output named instance_ip. The root module accesses it using module.webserver.instance_ip, which returns the public IP address of the instance created by the child module.

❓ Configuration

intermediate

Correctly referencing outputs from a nested module

You have a Terraform module db that outputs db_endpoint. How do you correctly expose this output in the root module so it can be used elsewhere?

Terraform

module "db" {
  source = "./modules/database"
}

output "database_endpoint" {
  value = ???
}

A db.db_endpoint

B module.database.db_endpoint

C output.db_endpoint

D module.db.db_endpoint

💡 Hint

Outputs from modules are accessed using module...

The correct syntax to access an output from a module is module... Here, module.db.db_endpoint correctly references the output.

❓ Architecture

advanced

Impact of missing outputs in Terraform modules

If a Terraform child module creates resources but does not define any outputs, what is the impact on the root module's ability to use information from those resources?

A Terraform will throw an error during plan because outputs are missing.

B The root module can still access all resource attributes automatically.

C The root module cannot access any information about the child module's resources directly.

D The root module can access outputs only if the child module has variables defined.

💡 Hint

Think about how Terraform shares data between modules.

Outputs are the only way for a child module to expose information to the root module. Without outputs, the root module cannot access resource details from the child module.

❓ security

advanced

Security considerations when exposing sensitive outputs from Terraform modules

A Terraform module outputs a sensitive value like a database password using sensitive = true. What happens if the root module references this output without marking it sensitive?

A Terraform will mask the value in CLI output and state files automatically.

B The root module must explicitly mark the output as sensitive to keep it hidden.

C Terraform will refuse to apply the configuration due to sensitivity mismatch.

D The sensitive value will be shown in CLI output and logs, risking exposure.

💡 Hint

Consider how Terraform handles sensitive outputs across module boundaries.

When a child module marks an output as sensitive, the root module must also mark its output referencing it as sensitive to prevent accidental exposure.

✅ Best Practice

expert

Best practice for outputting multiple values from a Terraform module

You want to output multiple related values from a Terraform module, such as instance ID, public IP, and private IP. Which approach is best to keep outputs clean and manageable?

A Combine all values into a single map output with keys for each value.

B Define separate outputs for each value: <code>instance_id</code>, <code>public_ip</code>, <code>private_ip</code>.

C Output a list containing all values in order without keys.

D Do not output these values; instead, access resources directly from the root module.

💡 Hint

Think about how to group related data for easier consumption.

Using a single map output groups related values logically, making it easier to access and maintain outputs from the root module.