Unable to display Public DNS when using aws ec2_instance module

Question

My EC2 instance module configuration for us-east-1 looks as below:

module "ec2_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "~> 5.2.0"
    
  for_each = toset(["one", "two", "three"])
    
  name = "instance-${each.key}"
  ami = "ami-0f34c5ae932e6f0e4"
  
  instance_type          = "t2.micro"
  key_name               = "ec2keypair"
  monitoring             = true
  vpc_security_group_ids = ["sg-0d1e7372e359bfa42"]
  subnet_id              = "subnet-0ff5469ab7c53e44b"
  user_data = file("apache-install.sh")
  
  tags = {
    "Name" = "Modules-Demo"
     Terraform   = "true"
     Environment = "dev"
  }
}

My output looks as below:

output "ec2_publicip" {
  description = "Public IP of an EC2 Instance"
  value = module.ec2_instance.*.public_ip
}

This is throwing below error:

Error: Unsupported attribute on c5-outputs.tf line 8, in output "ec2_publicip": 8: value = module.ec2_instance.*.public_ip This object does not have an attribute named "public_ip".

I have gone through the documentation and public_ip is showing as valid attribute.

Answer 1

You need to tell the module you want it to assign a public IP address to the instance:

module "ec2_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "~> 5.2.0"

  for_each = toset(["one", "two", "three"])

  name                        = "instance-${each.key}"
  ami                         = "ami-0f34c5ae932e6f0e4"
  instance_type               = "t2.micro"
  key_name                    = "ec2keypair"
  monitoring                  = true
  vpc_security_group_ids      = ["sg-0d1e7372e359bfa42"]
  subnet_id                   = "subnet-0ff5469ab7c53e44b"
  associate_public_ip_address = true # <---- add this line
  user_data = file("apache-install.sh")
  tags = {
    "Name" = "Modules-Demo"
    Terraform   = "true"
    Environment = "dev"
  }
}

Additionally, since the module is created using for_each, to get all of the outputs, you need to use the values built-in function:

output "ec2_publicip" {
  description = "Public IP of an EC2 Instance"
  value       = values(module.ec2_instance)[*].public_ip
}