Terraform using output from module - amazon-web-services

Question

I just started with Terraform infrastructure. Trying to create a vpc module that will contain code for vpc, subnets, internet gateway, rout table. Also creating a separate tf file for rds , which will refer to the vpc module and utilize the private subnets declared in vpc module.
Created a vpc module that has vpc.tf with following
provider "aws" {
region = var.region
}
terraform {
backend "s3" {}
}
resource "aws_vpc" "production-vpc" {
cidr_block = var.vpc_cidr
enable_dns_hostnames = true
tags = {
Name = "Dev-VPC"
}
}
// Private Subnets
resource "aws_subnet" "private-subnet-1" {
cidr_block = var.private_subnet_1_cidr
vpc_id = aws_vpc.production-vpc.id
availability_zone = "us-east-1a"
tags = {
Name = "Private-Subnet-1"
}
}
resource "aws_subnet" "private-subnet-2" {
cidr_block = var.private_subnet_2_cidr
vpc_id = aws_vpc.production-vpc.id
availability_zone = "us-east-1b"
tags = {
Name = "Private-Subnet-2"
}
}
The output.tf has following
output "private-subnet1-id" {
description = "Private Subnet1 Id"
value = aws_subnet.private-subnet-1.*.id
}
output "private-subnet2-id" {
description = "Private Subnet2 Id"
value = aws_subnet.private-subnet-2.*.id
}
The file is saved in folder \module\vpc folder
Created rds.tf as follows in folder \rds
provider "aws" {
region = var.region
}
terraform {
backend "s3" {}
}
module "vpc" {
source = "../module/vpc"
}
resource "aws_db_subnet_group" "subnetgrp" {
name = "dbsubnetgrp"
subnet_ids = [module.vpc.private-subnet1-id.id, module.vpc.private-subnet2-id.id]
}
When I run terraform plan , I get following error
Error: Unsupported attribute
on rds.tf line 16, in resource "aws_db_subnet_group" "subnetgrp":
16: subnet_ids = [module.vpc.private-subnet1-id.id, module.vpc.private-subnet2-id.id]
|----------------
| module.vpc.private-subnet1-id is tuple with 1 element
This value does not have any attributes.
Error: Unsupported attribute
on rds.tf line 16, in resource "aws_db_subnet_group" "subnetgrp":
16: subnet_ids = [module.vpc.private-subnet1-id.id, module.vpc.private-subnet2-id.id]
|----------------
| module.vpc.private-subnet2-id is tuple with 1 element
This value does not have any attributes.

Answer 1

You don't need the splat expression in the output.tf. Try the following,
output "private-subnet1-id" {
description = "Private Subnet1 Id"
value = aws_subnet.private-subnet-1.id
}
output "private-subnet2-id" {
description = "Private Subnet2 Id"
value = aws_subnet.private-subnet-2.id
}