I am creating a virtual machine on an OpenStack-based cloud using Terraform and I need to associate a floating IP with it.

The problem is that Terraform requires a port_id to associate the floating IP, but I cannot retrieve this value automatically from the created instance.

What I am trying to achieve

• Create a new VM

• Create or assign a floating IP

• Associate this floating IP with the VM in a single Terraform run, without manual steps

Current behavior

With my current approach, I must:

1. Run Terraform once to create the instance

2. Manually retrieve the port ID using:

openstack port list -f json | grep -B8 "10.20.30.202" | grep ID

1. Copy this port_id into Terraform

2. Run Terraform again

This is not acceptable for automation.

Terraform code

resource "openstack_compute_instance_v2" "instance" {
  name        = "test-vm"
  image_name  = "Debian 12 - Docker"
  flavor_name = "d2-2"
  key_pair    = "my-key"

  security_groups = [
    openstack_networking_secgroup_v2.secgroup.name
  ]

  network {
    name = "my-network"
  }
}

resource "openstack_networking_floatingip_associate_v2" "fip" {
  floating_ip = "172.10.0.6"
  port_id     = "d8c48c8b-a5cf-4dcf-9d90-544bb6a3f51e" # must be set manually
}

Question

How can I retrieve the correct port_id of the newly created instance directly in Terraform, so that the floating IP can be associated automatically in one apply?