vpc_id argument is not expected here - amazon-web-services

Question

I’m new to using modules in Terraform and I’m getting an error from my main.tf in my root module, saying “an argument vpc_id is not expected here” and this error is occurring for my “sg” module block at the bottom.
Here is my main.tf in my root module
access_key = var.my_access_key
secret_key = var.my_secret_key
region = var.region
}
provider "random" {
}
resource "random_id" "prefix" {
byte_length = 8
}
module "ec2" {
source = "./modules/ec2"
infra_env = var.infra_env
public_ssh_key = var.public_ssh_key
allow_rdp = module.sg.allow_rdp.id
allow_winrm = module.sg.allow_winrm.id
}
module "iam" {
source = "./modules/iam"
infra_env = var.infra_env
}
module "s3" {
source = "./modules/s3"
infra_env = var.infra_env
}
module "sg" {
source = "./modules/sg"
infra_env = var.infra_env
vpc_id = module.vpc.vpc_1.id
}
module "vpc" {
source = "./modules/vpc"
infra_env = var.infra_env
}
Here is the Main.tf of my “SG” module- I thought I only had to put “module.vpc.vpc_1.id” to get the input from that module
terraform {
required_version = ">= 1.1.5"
}
module "vpc" {
source = "../vpc"
infra_env = var.infra_env
}
# Allow WinRM to set adminstrator password
resource "aws_security_group" "allow_winrm" {
name = "allow_winrm"
description = "Allow access the instances via WinRM over HTTP and HTTPS"
vpc_id = module.vpc.vpc_1.id
ingress {
description = "Access the instances via WinRM over HTTP and HTTPS"
from_port = 5985
to_port = 5986
protocol = "tcp"
cidr_blocks = ["0.0.0.0/0"]
}
egress {
from_port = 0
to_port = 0
protocol = "-1"
cidr_blocks = ["0.0.0.0/0"]
}
tags = {
Name = "${var.infra_env}-allow-winrm"
}
}
# Allow RDP connectvity to EC2 instances
resource "aws_security_group" "allow_rdp" {
name = "allow_rdp"
description = "Allow access the instances via RDP"
vpc_id = module.vpc.vpc_1.id
ingress {
description = "Allow access the instances via RDP"
from_port = 3389
to_port = 3389
protocol = "tcp"
cidr_blocks = ["0.0.0.0/0"]
}
tags = {
Name = "${var.infra_env}-allow-rdp"
}
}
Here are the outputs for my VPC module, located in my VPC module:
output "subnet_1" {
value = aws_subnet.subnet_1
}
output "vpc_1" {
value = aws_vpc.vpc_1.id
}
output "gw_1" {
value = aws_internet_gateway.gw_1
}

Answer 1

There are a couple of problems with your code. In the outputs, you have written this:
output "vpc_1" {
value = aws_vpc.vpc_1.id
}
This means that the output value will already provide the VPC ID you want. It is enough to reference it only by name: module.vpc.vpc_1. More information about referencing module outputs is available in [1].
Second issue here is that you are trying to reference an output of a child module (VPC) in another child module (SG):
vpc_id = module.vpc.vpc_1.id
However, it would be enough to specify a variable in the child module (i.e., SG). For example, you could define a variable like this:
variable "vpc_id" {
description = "VPC ID."
type = string
}
Then, you would just write the above as:
vpc_id = var.vpc_id
When calling the SG module, you would use the following:
module "sg" {
source = "./modules/sg"
infra_env = var.infra_env
vpc_id = module.vpc.vpc_1
}
Note that the same change with var.vpc_id should be done everywhere in the SG module where module.vpc.vpc_1.id was referenced.
[1] https://www.terraform.io/language/values/outputs#accessing-child-module-outputs