Create instance and update DNS before destroying old instance

Terraform Providers Google
1

Note: Some resource attributes intentionally omitted for brevity.

Problem:

I have a google_compute_instance that triggers a re-creation if the boot_disk.image or metadata_startup_script change. I manage this via random_id.keepers like so:

resource "random_id" "suffix" {
  byte_length = 2

  keepers = {
    image = data.google_compute_image.image.self_link
    startup_script = data.template_file.startup_script.rendered
  }
}

resource "google_compute_instance" "instance" {
  metadata_startup_script = random_id.suffix.keepers.startup_script

  boot_disk {
    initialize_params {
      image = random_id.suffix.keepers.image
    }
  }

  lifecycle {
    create_before_destroy = true
  }
}

I use create_before_destroy so that the service this instance runs is highly available. The issue I’m having is that clients of this service connect via DNS.

resource "google_dns_record_set" "dns" {
  type         = "A"
  ttl          = 15
  rrdatas      = [google_compute_instance.instance.network_interface.0.network_ip]
}

Running the terraform apply results in the following order of operations:

random_id.suffix: Creating...
random_id.suffix: Creation complete after 0s
google_compute_instance.instance: Creating...
google_compute_instance.instance: Still creating...
google_compute_instance.instance: Creation complete after 13s
google_compute_instance.instance: Destroying...
google_compute_instance.instance: Still destroying...
google_dns_record_set.dns: Modifying...
google_dns_record_set.dns: Modifications complete after 2s
google_compute_instance.instance: Still destroying...

Once the replacement instance finishes creating it starts the destroy and the DNS modification at the same time.

I’m looking for a way to update the DNS and wait for the TTL to expire before destroying the old instance. Is this possible?