fix: make project_id as required input and update apphub_workload_uri output

Author: q2w

autogen/outputs.tf.tmpl

@@ -40,7 +40,7 @@ output "health_check_self_links" {
 output "apphub_workload_uri" {
   value = {
     workload_uri = "//compute.googleapis.com/projects${element(split("/projects", google_compute_region_instance_group_manager.mig.instance_group), 1)}"
-    workload_id  = substr(join("-", [tostring(google_compute_region_instance_group_manager.mig.name), md5(tostring(google_compute_region_instance_group_manager.mig.self_link))]), 0, 63)
+    workload_id  = substr(join("-", [tostring(google_compute_region_instance_group_manager.mig.name), md5(join("-", [var.region, var.project_id]))]), 0, 63)
   }
   description = "Workload URI in CAIS style to be used by Apphub."
 }

autogen/variables.tf.tmpl

@@ -19,7 +19,6 @@
 variable "project_id" {
   type        = string
   description = "The Google Cloud project ID"
-  default     = null
 }
 
 variable "region" {

docs/upgrading_to_mig_v13.0.md

@@ -0,0 +1,23 @@
+# Upgrading to MIG v13.0
+
+The v13.0 release of MIG is a backwards incompatible release. Now the `project_id` is required input variable. Earlier it was set to `null` by default. But the `terraform plan` would fail because `google_compute_zones` data block requires a non-null `project_id`.
+Users might be bypassing this by setting project at provider level and not providing `project_id` for mig module.
+
+## Migration Instructions
+
+### Explicitly provide project_id as input to the MIG module
+
+Users would need to provide project_id explicitly while using v13.0 of MIG.
+
+```diff
+module "mig" {
+  source  = "terraform-google-modules/vm/google//modules/mig"
+  version = "~> 12.0"
+
++ project_id        = var.project_id
+  region            = var.region
+  target_size       = var.target_size
+  hostname          = "mig-simple"
+  instance_template = module.instance_template.self_link
+}
+```

modules/mig/README.md

@@ -38,7 +38,7 @@ The current version is 2.X. The following guides are available to assist with up
 | mig\_timeouts | Times for creation, deleting and updating the MIG resources. Can be helpful when using wait\_for\_instances to allow a longer VM startup time. | <pre>object({<br>    create = string<br>    update = string<br>    delete = string<br>  })</pre> | <pre>{<br>  "create": "5m",<br>  "delete": "15m",<br>  "update": "5m"<br>}</pre> | no |
 | min\_replicas | The minimum number of replicas that the autoscaler can scale down to. This cannot be less than 0. | `number` | `2` | no |
 | named\_ports | Named name and named port. https://cloud.google.com/load-balancing/docs/backend-service#named_ports | <pre>list(object({<br>    name = string<br>    port = number<br>  }))</pre> | `[]` | no |
-| project\_id | The Google Cloud project ID | `string` | `null` | no |
+| project\_id | The Google Cloud project ID | `string` | n/a | yes |
 | region | The Google Cloud region where the managed instance group resides. | `string` | n/a | yes |
 | scaling\_schedules | Autoscaling, scaling schedule block. https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_autoscaler#scaling_schedules | <pre>list(object({<br>    disabled              = bool<br>    duration_sec          = number<br>    min_required_replicas = number<br>    name                  = string<br>    schedule              = string<br>    time_zone             = string<br>  }))</pre> | `[]` | no |
 | stateful\_disks | Disks created on the instances that will be preserved on instance delete. https://cloud.google.com/compute/docs/instance-groups/configuring-stateful-disks-in-migs | <pre>list(object({<br>    device_name = string<br>    delete_rule = string<br>  }))</pre> | `[]` | no |

modules/mig/metadata.yaml

@@ -83,6 +83,7 @@ spec:
       - name: project_id
         description: The Google Cloud project ID
         varType: string
+        required: true
       - name: region
         description: The Google Cloud region where the managed instance group resides.
         varType: string

modules/mig/outputs.tf

@@ -39,7 +39,7 @@ output "health_check_self_links" {
 output "apphub_workload_uri" {
   value = {
     workload_uri = "//compute.googleapis.com/projects${element(split("/projects", google_compute_region_instance_group_manager.mig.instance_group), 1)}"
-    workload_id  = substr(join("-", [tostring(google_compute_region_instance_group_manager.mig.name), md5(tostring(google_compute_region_instance_group_manager.mig.self_link))]), 0, 63)
+    workload_id  = substr(join("-", [tostring(google_compute_region_instance_group_manager.mig.name), md5(join("-", [var.region, var.project_id]))]), 0, 63)
   }
   description = "Workload URI in CAIS style to be used by Apphub."
 }

modules/mig/variables.tf

@@ -19,7 +19,6 @@
 variable "project_id" {
   type        = string
   description = "The Google Cloud project ID"
-  default     = null
 }
 
 variable "region" {