Changed google_compute_instance_group_manager target_size default to 0.

google/resource_compute_instance_group_manager.go

@@ -132,10 +132,9 @@ func resourceComputeInstanceGroupManagerCreate(d *schema.ResourceData, meta inte
 		return err
 	}
 
-	// Get group size, default to 1 if not given
-	var target_size int64 = 1
+	var targetSize int64 = 0
 	if v, ok := d.GetOk("target_size"); ok {
-		target_size = int64(v.(int))
+		targetSize = int64(v.(int))
 	}
 
 	// Build the parameter
@@ -143,7 +142,8 @@ func resourceComputeInstanceGroupManagerCreate(d *schema.ResourceData, meta inte
 		Name:             d.Get("name").(string),
 		BaseInstanceName: d.Get("base_instance_name").(string),
 		InstanceTemplate: d.Get("instance_template").(string),
-		TargetSize:       target_size,
+		TargetSize:       targetSize,
+		ForceSendFields:  []string{"TargetSize"},
 	}
 
 	// Set optional fields
@@ -256,7 +256,6 @@ func resourceComputeInstanceGroupManagerRead(d *schema.ResourceData, meta interf
 	d.Set("named_port", flattenNamedPorts(manager.NamedPorts))
 	d.Set("fingerprint", manager.Fingerprint)
 	d.Set("instance_group", manager.InstanceGroup)
-	d.Set("target_size", manager.TargetSize)
 	d.Set("self_link", manager.SelfLink)
 	update_strategy, ok := d.GetOk("update_strategy")
 	if !ok {
@@ -382,23 +381,19 @@ func resourceComputeInstanceGroupManagerUpdate(d *schema.ResourceData, meta inte
 		d.SetPartial("named_port")
 	}
 
-	// If size changes trigger a resize
+	// We won't ever see changes if target_size is unset
 	if d.HasChange("target_size") {
-		if v, ok := d.GetOk("target_size"); ok {
-			// Only do anything if the new size is set
-			target_size := int64(v.(int))
+		target_size := int64(d.Get("target_size").(int))
+		op, err := config.clientCompute.InstanceGroupManagers.Resize(
+			project, d.Get("zone").(string), d.Id(), target_size).Do()
+		if err != nil {
+			return fmt.Errorf("Error updating InstanceGroupManager: %s", err)
+		}
 
-			op, err := config.clientCompute.InstanceGroupManagers.Resize(
-				project, d.Get("zone").(string), d.Id(), target_size).Do()
-			if err != nil {
-				return fmt.Errorf("Error updating InstanceGroupManager: %s", err)
-			}
-
-			// Wait for the operation to complete
-			err = computeOperationWaitZone(config, op, project, d.Get("zone").(string), "Updating InstanceGroupManager")
-			if err != nil {
-				return err
-			}
+		// Wait for the operation to complete
+		err = computeOperationWaitZone(config, op, project, d.Get("zone").(string), "Updating InstanceGroupManager")
+		if err != nil {
+			return err
 		}
 
 		d.SetPartial("target_size")

google/resource_compute_instance_group_manager_test.go

@@ -39,6 +39,32 @@ func TestAccInstanceGroupManager_basic(t *testing.T) {
 	})
 }
 
+func TestAccInstanceGroupManager_targetSizeZero(t *testing.T) {
+	var manager compute.InstanceGroupManager
+
+	template := fmt.Sprintf("igm-test-%s", acctest.RandString(10))
+	igm := fmt.Sprintf("igm-test-%s", acctest.RandString(10))
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckInstanceGroupManagerDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: testAccInstanceGroupManager_targetSizeZero(template, igm),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckInstanceGroupManagerExists(
+						"google_compute_instance_group_manager.igm-basic", &manager),
+				),
+			},
+		},
+	})
+
+	if manager.TargetSize != 0 {
+		t.Errorf("Expected target_size to be 0, got %d", manager.TargetSize)
+	}
+}
+
 func TestAccInstanceGroupManager_update(t *testing.T) {
 	var manager compute.InstanceGroupManager
 
@@ -388,6 +414,43 @@ func testAccInstanceGroupManager_basic(template, target, igm1, igm2 string) stri
 	`, template, target, igm1, igm2)
 }
 
+func testAccInstanceGroupManager_targetSizeZero(template, igm string) string {
+	return fmt.Sprintf(`
+	resource "google_compute_instance_template" "igm-basic" {
+		name = "%s"
+		machine_type = "n1-standard-1"
+		can_ip_forward = false
+		tags = ["foo", "bar"]
+
+		disk {
+			source_image = "debian-cloud/debian-8-jessie-v20160803"
+			auto_delete = true
+			boot = true
+		}
+
+		network_interface {
+			network = "default"
+		}
+
+		metadata {
+			foo = "bar"
+		}
+
+		service_account {
+			scopes = ["userinfo-email", "compute-ro", "storage-ro"]
+		}
+	}
+
+	resource "google_compute_instance_group_manager" "igm-basic" {
+		description = "Terraform test instance group manager"
+		name = "%s"
+		instance_template = "${google_compute_instance_template.igm-basic.self_link}"
+		base_instance_name = "igm-basic"
+		zone = "us-central1-c"
+	}
+	`, template, igm)
+}
+
 func testAccInstanceGroupManager_update(template, target, igm string) string {
 	return fmt.Sprintf(`
 	resource "google_compute_instance_template" "igm-update" {

website/docs/r/compute_instance_group_manager.html.markdown

@@ -74,9 +74,9 @@ The following arguments are supported:
     restart all of the instances at once. In the future, as the GCE API matures
     we will support `"ROLLING_UPDATE"` as well.
 
-* `target_size` - (Optional) If not given at creation time, this defaults to 1.
-    Do not specify this if you are managing the group with an autoscaler, as
-    this will cause fighting.
+* `target_size` - (Optional, Default `0`) The target number of running instances for this managed
+    instance group. This value should always be explicitly set unless this resource is attached to
+     an autoscaler, in which case it should never be set.
 
 * `target_pools` - (Optional) The full URL of all target pools to which new
     instances in the group are added. Updating the target pools attribute does