Data source vs resource difference in Terraform - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a resource that creates an AWS S3 bucket.

Terraform

resource "aws_s3_bucket" "my_bucket" {
  bucket = [1]
}

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

A"my-unique-bucket-name"

Baws_s3_bucket.my_bucket

C"data.aws_s3_bucket.my_bucket"

Dbucket_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using a data source reference instead of a string for the bucket name.

Omitting quotes around the bucket name.

The resource block creates a new AWS S3 bucket with the specified name. The bucket name must be a string.

2fill in blank

medium

Complete the code to declare a data source that reads an existing AWS S3 bucket.

Terraform

data "aws_s3_bucket" "existing_bucket" {
  bucket = [1]
}

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

Abucket_name

Baws_s3_bucket.my_bucket

C"my-existing-bucket"

Dexisting_bucket_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using a resource reference instead of a string for the bucket name.

Forgetting to put quotes around the bucket name.

The data block reads information about an existing AWS S3 bucket. The bucket name must be a string literal.

3fill in blank

hard

Fix the error in referencing the bucket name from a data source in the resource block.

Terraform

resource "aws_s3_bucket_policy" "policy" {
  bucket = [1].bucket
  policy = jsonencode({
    Statement = []
  })
}

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

Adata.aws_s3_bucket_policy.existing_policy

Baws_s3_bucket.my_bucket

Caws_s3_bucket_policy.policy

Ddata.aws_s3_bucket.existing_bucket

Attempts:

3 left

💡 Hint

Common Mistakes

Referencing a resource instead of a data source.

Using the wrong attribute name.

To reference an existing bucket from a data source, use data.aws_s3_bucket.existing_bucket.bucket. This accesses the bucket attribute from the data source.

4fill in blank

hard

Fill both blanks to create a resource that uses a data source to get the VPC ID.

Terraform

data "aws_vpc" "selected" {
  filter {
    name   = [1]
    values = ["default"]
  }
}

resource "aws_subnet" "example" {
  vpc_id     = [2].id
  cidr_block = "10.0.1.0/24"
}

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

A"tag:Name"

Bdata.aws_vpc.selected

C"vpc-id"

Daws_vpc.default

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect filter names.

Referencing resources instead of data sources.

The data source filter uses the tag name to find the default VPC. The resource references the data source's ID attribute.

5fill in blank

hard

Fill all three blanks to create a resource that uses a data source to get an AMI ID and launch an EC2 instance.

Terraform

data "aws_ami" "ubuntu" {
  most_recent = true
  filter {
    name   = [1]
    values = ["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"]
  }
  owners = [[2]]
}

resource "aws_instance" "web" {
  ami           = [3].id
  instance_type = "t2.micro"
}

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

A"name"

B"099720109477"

Cdata.aws_ami.ubuntu

D"owner-id"

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect filter or owner keys.

Referencing the resource instead of the data source.

The data source filters AMIs by the name attribute. The owner ID is a string. The resource references the data source's ID attribute.

Practice

1. What is the main difference between a resource and a data source in Terraform?

easy

A. Resources and data sources both create infrastructure but in different clouds.

B. Resources create or manage infrastructure; data sources only read existing information.

C. Resources only read existing infrastructure; data sources create new infrastructure.

D. Resources are temporary; data sources are permanent.

Solution

1. Step 1: Understand resource role

   Resources in Terraform are used to create or manage cloud infrastructure components.

2. Step 2: Understand data source role

   Data sources are used to read information about existing infrastructure without changing it.

3. Final Answer:

   Resources create or manage infrastructure; data sources only read existing information. -> Option B

4. Quick Check:

   Resource = create/manage, Data source = read [OK]

Hint: Resources build; data sources just look up info [OK]

Common Mistakes:

• Thinking data sources create resources
• Confusing resource and data source roles
• Assuming both modify infrastructure
• Believing data sources are temporary

2. Which of the following is the correct syntax to declare a data source in Terraform?

easy

A. data "aws_ami" "example" {}

B. resource "aws_instance" "example" {}

C. source "aws_vpc" "example" {}

D. resource "data_aws_subnet" "example" {}

Solution

1. Step 1: Identify data source syntax

   Data sources use the keyword data followed by the type and name.

2. Step 2: Check options

   data "aws_ami" "example" {} uses data "aws_ami" "example" {}, which is correct syntax for a data source.

3. Final Answer:

   data "aws_ami" "example" {} -> Option A

4. Quick Check:

   Data source starts with 'data' keyword [OK]

Hint: Data sources start with 'data' keyword [OK]

Common Mistakes:

• Using 'resource' keyword for data sources
• Mixing 'source' keyword which doesn't exist
• Prefixing resource with 'data_' incorrectly
• Confusing resource and data source syntax

3. Given this Terraform snippet:

data "aws_vpc" "selected" {
  filter {
    name   = "tag:Name"
    values = ["main-vpc"]
  }
}

resource "aws_subnet" "example" {
  vpc_id     = data.aws_vpc.selected.id
  cidr_block = "10.0.1.0/24"
}

What does the data.aws_vpc.selected.id represent?

medium

A. The ID of an existing VPC filtered by tag "Name=main-vpc".

B. The ID of a subnet created inside the VPC.

C. A random VPC ID generated by Terraform.

D. The ID of a new VPC created by Terraform.

Solution

1. Step 1: Analyze data source usage

   The data "aws_vpc" "selected" block reads an existing VPC filtered by the tag "Name=main-vpc".

2. Step 2: Understand reference in resource

   The resource aws_subnet.example uses data.aws_vpc.selected.id to get the ID of that existing VPC to create a subnet inside it.

3. Final Answer:

   The ID of an existing VPC filtered by tag "Name=main-vpc". -> Option A

4. Quick Check:

   Data source reads existing VPC ID [OK]

Hint: Data source reads existing resource info [OK]

Common Mistakes:

• Thinking data source creates new VPC
• Confusing subnet ID with VPC ID
• Assuming random ID generation
• Using resource instead of data source for existing info

4. You wrote this Terraform code but get an error:

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
}

data "aws_vpc" "main" {
  id = aws_vpc.main.id
}

What is the problem?

medium

A. The data source block is missing a filter instead of id.

B. Data sources cannot reference resources in the same configuration.

C. You cannot use the same name for resource and data source.

D. The resource block is missing a provider configuration.

Solution

1. Step 1: Check naming conflict

   The resource and data source both use the name "main" which causes a naming conflict in Terraform.

2. Step 2: Terraform rules

   Terraform does not allow a resource and a data source to share the same type and name within the same module.

3. Final Answer:

   You cannot use the same name for resource and data source. -> Option C

4. Quick Check:

   Resource and data source names must be unique [OK]

Hint: Resource and data source names must differ [OK]

Common Mistakes:

• Thinking same names cause conflicts
• Believing you always need filters over id
• Assuming data sources can depend on resources
• Blaming missing provider config

5. You want to create a subnet in an existing VPC without recreating the VPC. Which Terraform approach is best?

hard

A. Use a resource block for the VPC and a resource block for the subnet.

B. Use a resource block for the subnet and ignore the VPC.

C. Use a data source block for both VPC and subnet.

D. Use a data source block to read the existing VPC and a resource block to create the subnet.

Solution

1. Step 1: Identify existing infrastructure

   The VPC already exists, so it should not be recreated or managed as a resource.

2. Step 2: Use data source for existing VPC

   Use a data source block to safely read the existing VPC's details without changing it.

3. Step 3: Create subnet resource

   Create a resource block for the subnet to add new infrastructure inside the existing VPC.

4. Final Answer:

   Use a data source block to read the existing VPC and a resource block to create the subnet. -> Option D

5. Quick Check:

   Data source reads existing; resource creates new [OK]

Hint: Read existing with data source; create new with resource [OK]

Common Mistakes:

• Trying to recreate existing VPC as resource
• Using data source to create subnet (not possible)
• Ignoring existing VPC and creating subnet without VPC ID
• Using resource for both causing conflicts