Description

I’m encountering Unsupported argument errors for cpu_core_count and cpu_threads_per_core when using module version 5.8.0 with AWS Provider 5.100.0. This setup has worked in the past, but now fails during terraform plan.

This appears to be related to older module versions passing CPU arguments unconditionally, even though they're no longer supported in AWS Provider v5.x. I found a similar issue in the repo that was previously closed without a resolution — I'm reopening the problem here, as it's still valid and blocking for users who can't yet upgrade to provider v6.

✋ I have searched the open/closed issues and my issue there is one issue but not resolved.

⚠️ Note

I have already tried the following:

1. Removed .terraform/
2. Re-initialized with terraform init
3. Re-ran terraform plan

Problem persists.

Versions

• Module version: 5.8.0

• Terraform version:

  Terraform v1.5.7
  

• Provider version(s):

  provider registry.terraform.io/hashicorp/aws v5.100.0
  

Reproduction Code [Required]

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = ">= 5.100.0"
    }
  }
}

provider "aws" {
  region = "us-west-2"
}

data "aws_ami" "worker_amazon_linux" {
  most_recent = true
  owners      = ["amazon"]
  filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
  }
}

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "4.0.2"
  # ...
}

resource "aws_iam_instance_profile" "ec2_worker_instance_profile" {
  # ...
}

resource "aws_security_group" "worker_sg" {
  # ...
}

resource "aws_key_pair" "ec2_worker_key" {
  # ...
}

module "ec2-instance_worker" {
  source                      = "terraform-aws-modules/ec2-instance/aws"
  version                     = "5.8.0"
  name                        = "example-worker"
  ami                         = data.aws_ami.worker_amazon_linux.id
  instance_type               = "t3.medium"
  subnet_id                   = module.vpc.private_subnets[0]
  associate_public_ip_address = false
  iam_instance_profile        = aws_iam_instance_profile.ec2_worker_instance_profile.name
  vpc_security_group_ids      = [aws_security_group.worker_sg.id]
  key_name                    = aws_key_pair.ec2_worker_key.key_name
  user_data                   = ""
  user_data_replace_on_change = false

  metadata_options = {
    http_endpoint               = "enabled"
    http_put_response_hop_limit = 1
    http_tokens                 = "required"
  }

  enable_volume_tags = true

  tags = {
    Name = "example-worker"
  }

  ignore_ami_changes = true
}

Run:

terraform init
terraform plan

Expected behavior

Terraform plan should complete successfully, without errors for invalid or deprecated arguments.

Actual behavior

Terraform fails with:

Error: Unsupported argument
on .terraform/modules/ec2-instance_worker/main.tf line 205, in resource "aws_instance" "ignore_ami":
  cpu_threads_per_core = var.cpu_threads_per_core
An argument named "cpu_threads_per_core" is not expected here.

Error: Unsupported argument
on .terraform/modules/ec2-instance_worker/main.tf line 204, in resource "aws_instance" "ignore_ami":
  cpu_core_count       = var.cpu_core_count
An argument named "cpu_core_count" is not expected here.
...

Additional context

• Upgrading to module v6.0.2 or AWS Provider v6.x resolves the issue since the module removed these arguments.
• Unfortunately, I’m not ready to move to AWS Provider v6 yet.
• This is a blocker since module versions before 6.0.0 are not compatible with AWS Provider 5.x without throwing errors due to these now-invalid arguments.

Please consider making a patch release for the 5.x module line that conditionally includes cpu_* arguments only if defined, or clarifying compatibility in the documentation.