terraform: ec2 machine change does not trigged dns change

Question

I've got simple code for many EC2 machines setup. It does not update DNS record after machine is changed. I need to run it second time - only then DNS will be changed. What am I doing wrong?

resource "aws_instance" "ec2" {
  for_each          = var.instances

  ami               = each.value.ami
  instance_type     = each.value.type
  ebs_optimized     = true
}

resource "cloudflare_record" "web" {
  for_each = var.instances

  zone_id  = var.cf_zone_id
  name     = "${each.key}.${var.env}.aws.${var.domain}."
  value    = aws_instance.ec2[each.key].public_ip
  type     = "A"
  ttl      = 1

  depends_on = [
    aws_instance.ec2
  ]
}

Answer 1

So, one thing about Terraform is that it provisions your infrastructure, but whatever happens with your infrastructure between your latest apply and now won't be reflected by the Terraform state file. If there is indeed a change in your infrastructure, then you would see it in the next Terraform plan. There is nothing wrong with what you're doing, only that you might have understood Terraform wrongly. There is a neat concept called "Immutable Infrastructure". Read it up in Hashicorp's blog: https://www.hashicorp.com/resources/what-is-mutable-vs-immutable-infrastructure