GCP compute instances feedback

[gaelL]

General information:

• Operating System: Cycloid SaaS (InfraImport)
• Terracognita version / tag: Cycloid SaaS (InfraImport)
• Did you build Terracognita from sources or did you use the Docker image: Cycloid SaaS (InfraImport)

Describe the bug:

In the shared generated Terraform file I identified 3 issues

1) book disk definition

The actual generated code is working with plan/apply but is not valid from a Terraform point of view to recreate the instance:

  boot_disk {
    auto_delete = true
    device_name = "instance-1"
    initialize_params {
      image = "https://www.googleapis.com/compute/v1/projects/debian-cloud/global/images/debian-10-buster-v20220310"
      size  = 10
      type  = "pd-balanced"
    }
    
    mode   = "READ_WRITE"
    source = "https://www.googleapis.com/compute/v1/projects/cycloid-demo/zones/europe-west1-b/disks/instance-1"
  }

As you can see initialize_params is used in addition to source parameter. Which raise an issue when you try to apply the code to recreate the VM after a destroy eg https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_instance#initialize_params

Parameters for a new disk that will be created alongside the new instance. Either initialize_params or source must be set.

Looking on the generated code, Terracognita imported my google_compute_disk in a dedicated resource :

resource "google_compute_disk" "europe_west1_b_cycloid_demo_demo_front_demo" {
...

So I think the expected generated code would have been using source with interpolated value like this:

source = google_compute_disk.europe_west1_b_cycloid_demo_demo_front_demo.self_link

2) Instance resize usecase issue

A variable have been defined to change the machine_type eg machine_type = var.google_compute_instance_cycloid_demo_europe_west1_b_instance_1_machine_type

Giving a try to change it actually want to replace (destroy/recreate) the compute instance.

machine_type Note: If you want to update this value (resize the VM) after initial creation, you must set allow_stopping_for_update to true.

To avoid this behavior it could be great to add the following Terraform flag by default on instance definition

allow_stopping_for_update = true

allow_stopping_for_update - (Optional) If true, allows Terraform to stop the instance to update its properties. If you try to update a property that requires stopping the instance without setting this field, the update will fail.

3) ephemeral nat_ip issue when destroy/create

The actual generated code for the network part is the following

  network_interface {
    access_config {
      nat_ip       = "34.79.210.126"
      network_tier = "PREMIUM"
    }   

If I destroy/recreate the instance I got this error

Error: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].accessConfigs[0].natIP': '34.79.154.138'. The specified external IP address '34.79.154.138' was not found in region 'europe-west1'., invalid

Looking on terraform doc:

nat_ip - (Optional) The IP address that will be 1:1 mapped to the instance's network ip. If not given, one will be generated.

This is due to the fact nat_api can be static or ephemeral eg

In case of a static IP it's ok to give a fixed value, or import a compute_address resource and use interpolation.

In case of an ephemeral IP address it would be better to not specify this parameter.

Additional context

resource "google_compute_disk" "europe_west1_b_cycloid_demo_demo_front_demo" {
  labels = {
    project = "obs"
  }

  image                     = "https://www.googleapis.com/compute/v1/projects/debian-cloud/global/images/debian-10-buster-v20220310"
  name                      = "cycloid-demo-demo-front-demo"
  physical_block_size_bytes = 4096
  project                   = "cycloid-demo"
  size                      = 10
  type                      = "pd-standard"
  zone                      = "europe-west1-b"
}

resource "google_compute_instance" "cycloid_demo_europe_west1_b_instance_1" {
  labels = {
    project = "obs"
  }

  boot_disk {
    auto_delete = true
    device_name = "instance-1"
    initialize_params {
      image = "https://www.googleapis.com/compute/v1/projects/debian-cloud/global/images/debian-10-buster-v20220310"
      size  = 10
      type  = "pd-balanced"
    }

    mode   = "READ_WRITE"
    source = "https://www.googleapis.com/compute/v1/projects/cycloid-demo/zones/europe-west1-b/disks/instance-1"
  }

  confidential_instance_config {
    enable_confidential_compute = false
  }

  machine_type = var.google_compute_instance_cycloid_demo_europe_west1_b_instance_1_machine_type
  name         = "instance-1"
  network_interface {
    access_config {
      nat_ip       = "34.79.154.138"
      network_tier = "PREMIUM"
    }

    network            = "https://www.googleapis.com/compute/v1/projects/cycloid-demo/global/networks/default"
    network_ip         = "10.132.15.218"
    subnetwork         = "https://www.googleapis.com/compute/v1/projects/cycloid-demo/regions/europe-west1/subnetworks/default"
    subnetwork_project = "cycloid-demo"
  }

  project = "cycloid-demo"
  scheduling {
    automatic_restart   = true
    on_host_maintenance = "MIGRATE"
  }

  service_account {
    email  = "[email protected]"
    scopes = ["https://www.googleapis.com/auth/devstorage.read_only", "https://www.googleapis.com/auth/logging.write", "https://www.googleapis.com/auth/service.management.readonly", "https://www.googleapis.com/auth/servicecontrol", "https://www.googleapis.com/auth/trace.append", "https://www.googleapis.com/auth/monitoring.write"]
  }

  shielded_instance_config {
    enable_integrity_monitoring = true
    enable_vtpm                 = true
  }

  zone = "europe-west1-b"
}