Dynamic blocks vs for_each decision in Terraform - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to iterate over a collection of subnet CIDRs using for_each.

Terraform

resource "aws_subnet" "example" {
  for_each = [1]
  vpc_id     = var.vpc_id
  cidr_block = each.value
}

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Aeach.value

Bvar.vpc_id

Caws_vpc.main

Dvar.subnet_cidrs

Attempts:

3 left

💡 Hint

Common Mistakes

Using a single value instead of a collection for for_each.

Confusing for_each with count.

The for_each argument expects a map or set of strings to iterate over. Here, var.subnet_cidrs is a collection of CIDR blocks for subnets.

2fill in blank

medium

Complete the dynamic block to add multiple ingress rules inside a security group.

Terraform

resource "aws_security_group" "example" {
  name        = "example-sg"
  description = "Example security group"

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

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Avar.vpc_id

Bvar.ingress_rules

Caws_subnet.example

Dvar.subnet_cidrs

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning a non-collection value to for_each in dynamic block.

Using resource references instead of variables for rules.

The for_each inside a dynamic block should be assigned to a collection of ingress rule objects, here var.ingress_rules.

3fill in blank

hard

Fix the error in this dynamic block that tries to create multiple tags but uses incorrect syntax.

Terraform

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

  dynamic "tag" {
    for_each = var.tags
    content {
      [1] = tag.key
      value       = tag.value
    }
  }
}

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Akey

Btag_key

Ctags

Dtag

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'tags' instead of 'key' inside the content block.

Not providing both key and value attributes.

Inside a dynamic block for tags, the key should be key and the value should be value. Here, key = tag.key and value = tag.value is the correct pattern. The blank expects the key name, which is key.

4fill in blank

hard

Fill both blanks to correctly use for_each and dynamic block to create multiple EBS volumes attached to an instance.

Terraform

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

  dynamic "ebs_block_device" {
    for_each = [1]
    content {
      device_name = ebs_block_device.value.device_name
      volume_size = [2]
    }
  }
}

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Avar.ebs_volumes

Bvar.volume_sizes

Cebs_block_device.value.size

Debs_block_device.value.volume_size

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable that is not a collection for for_each.

Incorrect attribute name for volume size.

The for_each should iterate over var.ebs_volumes, which is a collection of volume objects. The volume size is accessed as ebs_block_device.value.volume_size inside the dynamic block.

5fill in blank

hard

Fill all three blanks to create multiple IAM policy statements using dynamic blocks with for_each.

Terraform

resource "aws_iam_role" "example" {
  name = "example-role"

  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Action = "sts:AssumeRole"
      Effect = "Allow"
      Principal = {
        Service = "ec2.amazonaws.com"
      }
    }]
  })
}

data "aws_iam_policy_document" "example" {
  dynamic "statement" {
    for_each = [1]
    content {
      effect    = "Allow"
      actions   = statement.value.[2]
      resources = statement.value.[3]
    }
  }
}

resource "aws_iam_role_policy" "example" {
  name   = "example-policy"
  role   = aws_iam_role.example.id
  policy = data.aws_iam_policy_document.example.json
}

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Avar.policies

Bactions

Cresources

Dpolicy_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect keys for actions or resources.

Not using a map for for_each.

The for_each iterates over var.policies, a map of policy statements. The action and resource keys inside each policy are actions and resources respectively.