in google_compute_instance_group_manager if target_size is set to 0 value get ignored

[dgolja]

Hi there,

In google_compute_instance_group_manager if you set target_size to 0 the value get ignored and the default value of 1 get applied at the first apply. Similar issue when you try to change the value from a non zero value to zero. Terraform will detect the change however when applying the plan the value will not got changed to 0.

Terraform Version

• terraform v0.96
• terraform v0.97
• terraform v0.98

Affected Resource(s)

Please list the resources as a list, for example:

• google_compute_instance_group_manager

Terraform Configuration Files

resource "google_compute_instance_template" "template" {
  name_prefix = "template-server"

  region = "${var.region}"

  lifecycle {
    create_before_destroy = true
  }

  network_interface {
    network = "default"
  }

  machine_type         = "f1-micro"
  can_ip_forward       = false

  scheduling {
    automatic_restart   = true
    on_host_maintenance = "TERMINATE"
  }

  // Create a new boot disk from an image
  disk {
    source_image = "projects/ubuntu-os-cloud/global/images/ubuntu-1604-xenial-v20170516"
    disk_type    = "pd-ssd"
    auto_delete  = true
    boot         = true
  }


  service_account {
    scopes = [ ]
  }

}

resource "google_compute_instance_group_manager" "group_manager" {
  name        = "instance-group-tf-bug"

  base_instance_name = "servers"
  instance_template  = "${google_compute_instance_template.template.self_link}"
  update_strategy    = "NONE"

  zone        = "us-central1-a"
  target_size = 0
}

Debug Output

google_compute_instance_group_manager.group_manager: Creating...
  base_instance_name: "" => "servers"
  fingerprint:        "" => "<computed>"
  instance_group:     "" => "<computed>"
  instance_template:  "" => "https://www.googleapis.com/compute/v1/projects/cloud-staging-168820/global/instanceTemplates/template-server0028f8764b2b18e1b29f3ea74a"
  name:               "" => "instance-group-tf-bug"
  project:            "" => "<computed>"
  self_link:          "" => "<computed>"
  target_size:        "" => "0"
  update_strategy:    "" => "NONE"
  zone:               "" => "us-central1-a"

Expected Behavior

Inttance group number of instances should be 0 and no instances should be created.

Actual Behavior

Instance group number of instances is 1

Steps to Reproduce

1. terraform apply

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