Why dynamic blocks reduce repetition in Terraform - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a dynamic block in Terraform.

Terraform

dynamic "[1]" {
  for_each = var.items
  content {
    cidr_blocks = [each.value]
  }
}

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

Aresource

Bitem

Cblock

Dingress

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'resource' instead of the block name.

Using 'block' which is not a valid block name.

Using 'item' which is a variable name, not a block.

The dynamic block name should match the block you want to repeat, such as ingress for security group rules.

2fill in blank

medium

Complete the code to access each item in the dynamic block.

Terraform

content {
  cidr_blocks = [each.value.[1]]
}

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

Acidr_block

Bcidr

Ccidr_blocks

Dcidrblock

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'cidr' which is incomplete.

Using 'cidr_blocks' which is the list, not the property.

Using 'cidrblock' which is misspelled.

Each item in the list should have a property named cidr_block to access the CIDR range.

3fill in blank

hard

Fix the error in the dynamic block to correctly iterate over a list.

Terraform

dynamic "ingress" {
  for_each = [1]
  content {
    from_port   = each.value.from_port
    to_port     = each.value.to_port
    protocol    = each.value.protocol
  }
}

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

Avar.ingress_rules

Bvar.ingress_rule

Cvar.ingress

Dvar.rules

Attempts:

3 left

💡 Hint

Common Mistakes

Using singular 'ingress_rule' which is not a list.

Using a generic 'rules' which may not exist.

Using 'ingress' which may be a block name, not a variable.

The variable should be the list of ingress rules, typically named ingress_rules.

4fill in blank

hard

Fill both blanks to add the Name tag to the resource.

Terraform

resource "aws_instance" "example" {
  ami           = var.ami
  instance_type = var.instance_type

  tags = {
    [1] = [2]
  }
}

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

AName

Bvar.name

CEnvironment

Dvar.environment

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names as keys instead of strings.

Mixing up keys and values.

Using incorrect variable names.

The tag key is 'Name' and its value comes from var.name.

5fill in blank

hard

Fill all three blanks to define a dynamic block for multiple security group egress rules.

Terraform

dynamic "egress" {
  for_each = [1]
  content {
    from_port   = each.value.[2]
    to_port     = each.value.[3]
    protocol    = each.value.protocol
  }
}

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

Avar.egress_rules

Bfrom_port

Cto_port

Dvar.rules

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable that is not a list.

Swapping 'from_port' and 'to_port' names.

Using generic variable names like 'rules' without context.

The dynamic block iterates over var.egress_rules, accessing from_port and to_port properties for each rule.

Practice

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

easy

A. They replace the need for variables in Terraform configurations.

B. They improve the speed of Terraform plan and apply operations.

C. They reduce repetition by generating multiple nested blocks automatically.

D. They allow Terraform to run without a backend configuration.

Solution

1. Step 1: Understand the purpose of dynamic blocks

   Dynamic blocks let you create repeated nested blocks from a list or map without manually copying code.

2. Step 2: Compare benefits

   This reduces repetition and keeps code clean and scalable, unlike options about speed, variables, or backend.

3. Final Answer:

   They reduce repetition by generating multiple nested blocks automatically. -> Option C

4. Quick Check:

   Dynamic blocks reduce repetition = C [OK]

Hint: Dynamic blocks create repeated blocks from lists automatically [OK]

Common Mistakes:

• Thinking dynamic blocks speed up Terraform execution
• Confusing dynamic blocks with variables
• Believing dynamic blocks remove backend needs

2. Which of the following is the correct syntax to start a dynamic block in Terraform?

easy

A. dynamic "block_name" { for_each = var.list }

B. dynamic block_name { for_each = var.list }

C. dynamic block_name = var.list { }

D. dynamic "block_name" = var.list { }

Solution

1. Step 1: Recall dynamic block syntax

   Dynamic blocks use the keyword dynamic followed by the block name in quotes, then a block with for_each.

2. Step 2: Match syntax to options

   Only dynamic "block_name" { for_each = var.list } matches the correct syntax: dynamic "block_name" { for_each = var.list }.

3. Final Answer:

   dynamic "block_name" { for_each = var.list } -> Option A

4. Quick Check:

   Correct dynamic block syntax = D [OK]

Hint: Dynamic block name must be in quotes after keyword dynamic [OK]

Common Mistakes:

• Omitting quotes around block name
• Using equals sign instead of braces
• Placing for_each outside the block

3. Given this Terraform snippet:

variable "ports" { default = [80, 443] }

resource "aws_security_group" "example" {
  name = "example"

  dynamic "ingress" {
    for_each = var.ports
    content {
      from_port   = ingress.value
      to_port     = ingress.value
      protocol    = "tcp"
      cidr_blocks = ["0.0.0.0/0"]
    }
  }
}

How many ingress blocks will be created in the security group?

medium

A. Depends on AWS region

B. 1

C. 0

D. 2

Solution

1. Step 1: Analyze the for_each list

   The variable ports contains two values: 80 and 443.

2. Step 2: Count dynamic block iterations

   The dynamic block creates one ingress block per item in var.ports, so 2 blocks total.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   List length = number of blocks = 2 [OK]

Hint: Dynamic blocks create one nested block per list item [OK]

Common Mistakes:

• Assuming only one block is created
• Thinking AWS region affects block count
• Confusing dynamic block with static block

4. Identify the error in this Terraform dynamic block snippet:

dynamic "egress" {
  for_each = var.rules
  content = {
    from_port   = egress.value.from
    to_port     = egress.value.to
    protocol    = "tcp"
  }
}

medium

A. Incorrect use of equals sign for content block

B. Missing quotes around block name "egress"

C. for_each must be outside the dynamic block

D. Variable var.rules cannot be used in dynamic blocks

Solution

1. Step 1: Check dynamic block content syntax

   The content must be a block, not assigned with equals sign.

2. Step 2: Identify correct syntax

   Correct syntax uses content { ... } without equals sign. The snippet incorrectly uses content = { ... }.

3. Final Answer:

   Incorrect use of equals sign for content block -> Option A

4. Quick Check:

   content block uses braces, no equals sign = B [OK]

Hint: Use content { } block, not content = { } [OK]

Common Mistakes:

• Using equals sign with content
• Placing for_each outside dynamic block
• Misquoting block name

5. You want to create multiple lifecycle_rule blocks in an aws_s3_bucket resource using a dynamic block. Your variable is a map with keys as rule names and values as rule details. Which approach correctly uses dynamic blocks to reduce repetition and handle the map structure?

hard

A. Use for_each = var.rules and access each rule with lifecycle_rule.key only inside content block.

B. Use for_each = var.rules and access each rule with lifecycle_rule.value inside content block.

C. Use count = length(var.rules) and index into var.rules inside content block.

D. Manually write each lifecycle_rule block without dynamic blocks.

Solution

1. Step 1: Understand dynamic block with map variable

   When using a map, for_each iterates over key-value pairs. The value is accessed with lifecycle_rule.value.

2. Step 2: Identify correct usage

   Use for_each = var.rules and access each rule with lifecycle_rule.value inside content block. correctly uses for_each = var.rules and accesses lifecycle_rule.value inside the content block to get rule details.

3. Final Answer:

   Use for_each = var.rules and access each rule with lifecycle_rule.value inside content block. -> Option B

4. Quick Check:

   Map iteration uses .value for content = A [OK]

Hint: Use .value to access map values inside dynamic block content [OK]

Common Mistakes:

• Using only .key without .value for map data
• Using count instead of for_each for maps
• Writing blocks manually instead of dynamic