Terraform: How to prevent ASG ec2 instance coming up before NAT Gateway is created

Thanks to jbardin https://github.com/hashicorp/terraform/issues/14056

In order to fix this you need to use an output from your VPC module. You can use the aws_nat_gateway attribute public_ip but since I had a route created after the aws_nat_gateway I used that instead. I then made a dummy variable and dummy resource in my Jenkins module.

resource "null_resource" "dummy" {
  provisioner "local-exec" {
    command = "echo ${var.dummy}"
  }
}

Make sure you assign that dummy variable to the output you have chosen. Also it needs to be a string. dummy = "${join(",", module.vpc.private_nat_gw_routes)}"

After that I used depends_on = ["null_resource.dummy"] on my ASG resource. This made that resource wait until after the NAT Gateway + routes were created but doesn't have the nasty side effect of recreating the resource every time.

No changes. Infrastructure is up-to-date.

This means that Terraform did not detect any differences between your
configuration and real physical resources that exist. As a result, no
actions need to be performed