Outputs as documentation in Terraform - Mini Project: Build & Apply

Outputs as documentation

📖 Scenario: You are setting up a simple cloud infrastructure using Terraform. You want to make sure that after deployment, important information about your resources is easy to find and understand. Outputs in Terraform help you document and share key details about your infrastructure.

🎯 Goal: Create Terraform outputs that clearly document the important attributes of your deployed resources, so anyone can quickly see the essential information after deployment.

📋 What You'll Learn

Create a Terraform variable for the instance name

Define a resource block for an AWS EC2 instance with the given name

Add outputs to show the instance ID and public IP

Use outputs to document the instance name and instance type

💡 Why This Matters

🌍 Real World

Outputs in Terraform help teams quickly find important information about deployed resources without searching through code or cloud consoles.

💼 Career

Knowing how to use outputs for documentation is essential for cloud engineers to communicate infrastructure details clearly and maintain infrastructure as code.

1

Create a Terraform variable for the instance name

Write a Terraform variable block named instance_name with type string and default value "my-instance".

Terraform

# Your code here

Hint

Use the variable block with type and default attributes.

2

Define an AWS EC2 instance resource using the variable

Write a Terraform resource block named aws_instance with resource name example. Set the ami to "ami-12345678", instance_type to "t2.micro", and tags with Name set to the variable instance_name.

Terraform

variable "instance_name" {
  type    = string
  default = "my-instance"
}

# Your code here

Hint

Use resource "aws_instance" "example" and set the attributes exactly as specified.

3

Add outputs for instance ID and public IP

Write two Terraform output blocks named instance_id and instance_public_ip. Set their value to aws_instance.example.id and aws_instance.example.public_ip respectively.

Terraform

variable "instance_name" {
  type    = string
  default = "my-instance"
}

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  tags = {
    Name = var.instance_name
  }
}

# Your code here

Hint

Use output blocks with the exact names and values.

4

Add outputs to document instance name and instance type

Write two Terraform output blocks named instance_name_output and instance_type_output. Set their value to var.instance_name and aws_instance.example.instance_type respectively. Add description attributes explaining these outputs as documentation.

Terraform

variable "instance_name" {
  type    = string
  default = "my-instance"
}

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  tags = {
    Name = var.instance_name
  }
}

output "instance_id" {
  value = aws_instance.example.id
}

output "instance_public_ip" {
  value = aws_instance.example.public_ip
}

# Your code here

Hint

Add description attributes to outputs to explain their purpose.

Practice

1. What is the main purpose of output blocks in Terraform?

easy

A. To write resource creation logic

B. To define variables for input values

C. To display important information after infrastructure is created

D. To configure provider settings

Solution

1. Step 1: Understand output block role

   Output blocks are used to show key information after Terraform finishes applying changes.

2. Step 2: Differentiate from other blocks

   Variables define inputs, providers configure cloud access, and resources create infrastructure, so outputs are for displaying results.

3. Final Answer:

   To display important information after infrastructure is created -> Option C

4. Quick Check:

   Outputs = display info [OK]

Hint: Outputs show info after apply, not inputs or configs [OK]

Common Mistakes:

• Confusing outputs with variables
• Thinking outputs create resources
• Assuming outputs configure providers

2. Which of the following is the correct syntax to define an output with a description in Terraform?

easy

A. output ip_address { value = aws_instance.web.public_ip description = "Public IP address" }

B. output "ip_address" { value = aws_instance.web.public_ip description = "Public IP address" }

C. output "ip_address" { value = aws_instance.web.public_ip } description = "Public IP address"

D. output "ip_address" { value = aws_instance.web.public_ip desc = "Public IP address" }

Solution

1. Step 1: Check output block structure

   An output block requires a name, a value, and optionally a description inside curly braces.

2. Step 2: Verify correct syntax

   The correct syntax places each attribute on its own line or separated properly; output "ip_address" { value = aws_instance.web.public_ip description = "Public IP address" } shows the correct format with value and description.

3. Final Answer:

   output "ip_address" { value = aws_instance.web.public_ip description = "Public IP address" } -> Option B

4. Quick Check:

   Output syntax = name, value, description [OK]

Hint: Output blocks need name, value, description inside braces [OK]

Common Mistakes:

• Missing quotes around output name
• Placing description outside the block
• Using incorrect attribute names

3. Given this Terraform output block:

output "db_password" {
  value       = aws_db_instance.main.password
  sensitive   = true
  description = "The database password"
}

What will happen when you run terraform apply?

medium

A. The password will not be shown in the output because it is marked sensitive

B. Terraform will throw a syntax error due to sensitive attribute

C. The password will be shown in the output after apply

D. The password will be printed in plain text in the logs

Solution

1. Step 1: Understand sensitive attribute effect

   Marking an output as sensitive hides its value from the standard output to protect secrets.

2. Step 2: Predict terraform apply behavior

   Terraform will apply changes but will not display the sensitive value in the output summary.

3. Final Answer:

   The password will not be shown in the output because it is marked sensitive -> Option A

4. Quick Check:

   sensitive output hides value [OK]

Hint: Sensitive outputs hide values after apply [OK]

Common Mistakes:

• Assuming sensitive outputs print values
• Thinking sensitive causes errors
• Confusing sensitive with encryption

4. You wrote this output block:

output "instance_ip" {
value = aws_instance.web.public_ip
}

Terraform shows a warning about missing description. How do you fix it?

medium

A. Rename the output to "instance_ip_address"

B. Remove the output block completely

C. Change value to a string literal

D. Add a description attribute inside the output block

Solution

1. Step 1: Identify missing description

   Terraform recommends adding descriptions to outputs for clarity and documentation.

2. Step 2: Add description attribute

   Include a line like description = "Public IP of the instance" inside the output block to fix the warning.

3. Final Answer:

   Add a description attribute inside the output block -> Option D

4. Quick Check:

   Outputs need descriptions for docs [OK]

Hint: Add description attribute to output blocks [OK]

Common Mistakes:

• Ignoring description warnings
• Changing output name unnecessarily
• Removing output instead of fixing

5. You want to output a list of public IPs from multiple instances created with a for_each in Terraform. Which output block correctly documents and outputs this list?

hard

A. output "instance_ips" {
value = [for inst in aws_instance.web : inst.public_ip]
description = "List of public IPs for all web instances"
}

B. output "instance_ips" {
value = aws_instance.web.public_ip
description = "List of public IPs for all web instances"
}

C. output "instance_ips" {
value = tolist(aws_instance.web.public_ip)
description = "List of public IPs for all web instances"
}

D. output "instance_ips" {
value = aws_instance.web.public_ip[0]
description = "List of public IPs for all web instances"
}

Solution

1. Step 1: Understand for_each resource outputs

   When using for_each, resources are a map, so to get all public IPs, a for expression is needed to collect them.

2. Step 2: Check output value expression

   output "instance_ips" { value = [for inst in aws_instance.web : inst.public_ip] description = "List of public IPs for all web instances" } uses a for expression to iterate over all instances and extract public_ip, which is correct and documented with description.

3. Final Answer:

   output "instance_ips" { value = [for inst in aws_instance.web : inst.public_ip] description = "List of public IPs for all web instances" } -> Option A

4. Quick Check:

   Use for expression to output list from for_each [OK]

Hint: Use for expression to collect values from for_each resources [OK]

Common Mistakes:

• Using direct attribute without iteration
• Accessing only first element
• Using incorrect syntax for list extraction