Terraform Error while Passing output variable from one module to another

Question

I am using two modules vpc and lb and passing an output varibale in vcp module to lb module as below in the code. But I am getting following error -

Error: Unsupported attribute

  on main.tf line 35, in module "lb":
  35:   vpc-id = module.vpc.vpc-id

This value does not have any attributes.

Here is code - main.tf

provider "aws" {
  shared_credentials_file = "~/.aws/credentials"
  region =var.region      
}
# Include modules
module "vpc" {
  count = var.create_default_vpc ? 1:0
  source = "./modules/vpc"
  region = var.region
  zones = var.zones
}

module "lb" {
  source  = "./modules/lb"
  image = var.image
  instance_type = var.instance_type
  vpc-id = module.vpc.vpc-id
}

./modules/vpc/vpc.tf

resource "aws_vpc" "xcloud-vpc" {
  cidr_block       = "10.0.0.0/16"
  enable_dns_hostnames = true

  tags = {
    Name = "xcloud-vpc"
  }
}

./modules/vpc/vpc-output.tf

output "vpc-id" {
  value = aws_vpc.xcloud-vpc.id
}

./modules/lb/lb.tf

resource "aws_security_group" "allow_http" {
  name        = "xcloud-sg-allow-http"
  description = "Allow HTTP & ICMP inbound connections"
  vpc_id = var.vpc-id
  # vpc_id = module.vpc.vpc-id
  <some more ingress, egress code>

./modules/lb/lb-vars.tf

variable image {}
variable instance_type {}
variable vpc-id{}

Though I am passing vpc-id = module.vpc.vpc-id while including "lb" module in the main.tf , the above error is given for this line of code. Any pointer will be appreciated.

Marcin Marcin · Accepted Answer · 2020-12-22T10:39:28

Since you are using count in your module, you should refer to individual instances of the module, even if you have only one. So in your case, it would be:

vpc_id = module.vpc[0].vpc-id

Terraform Error while Passing output variable from one module to another

1 Answers