GCP filestore restore procedure to also update terraform config

docs/howto/filesystem-backups/restore-filesystem.md

@@ -17,16 +17,32 @@ Due to the length of the steps listed in that document, we will not repeat them
 ## GCP
 
 ```{note}
-We follow GCP's guidance for [restoring fileshares from a backup](https://cloud.google.com/filestore/docs/backup-restore#restore)
+We follow GCP's guidance for [restoring fileshares from a backup](https://cloud.google.com/filestore/docs/backup-restore#restore).
 ```
 
-To restore a share on a Filestore instance on GCP, we follow the documentation
-linked above. In short, this involves:
+To restore a share on a Filestore instance on GCP, we start by following the
+documentation linked above. In short, this involves:
 
 1. [Go to the Filestore instances page](https://console.cloud.google.com/filestore/instances) in the GCP console
-1. Click the instance ID of the Filestore you want to restore and click the "Backups" tab
-1. Locate the backup you want to restore from (most likely the most recently created), and click (...) "More actions"
-1. Click "Restore backup" and then select "Source instance"
-1. Click "Restore" and complete the dialog box that appears
+2. Click the instance ID of the Filestore you want to restore and click the "Backups" tab
+3. Locate the backup you want to restore from (most likely the most recently created), and click (...) "More actions"
+4. Click "Restore backup" and then select "Source instance"
+5. Click "Restore" and complete the dialog box that appears
 
-This should successfully restore the Filestore instance to its last backed-up state
+This should successfully restore the Filestore instance to its last backed-up state.
+
+Once this is done, you should also set the terraform variable `source_backup` to
+reference this web console change. Practically, you should configure something
+like below in the `terraform/gcp/projects/$CLUSTER_NAME.tfvars` file:
+
+```
+filestores = {
+  "filestore" : {
+    # ...
+    source_backup : "projects/<gcp project name>/locations/<filestore region>/backups/<backup name>",
+  },
+}
+```
+
+You can determine the value of `source_backup` by trying a `terraform plan`
+which should present the value in an associated error.

terraform/gcp/projects/pilot-hubs.tfvars

@@ -21,7 +21,10 @@ core_node_machine_type = "n2-highmem-4"
 enable_network_policy  = true
 
 filestores = {
-  "filestore" : { capacity_gb : 5120 }
+  "filestore" : {
+    capacity_gb : 5120,
+    source_backup : "projects/two-eye-two-see/locations/us-central1/backups/test",
+  },
 }
 enable_filestore_backups = true
 

terraform/gcp/storage.tf

@@ -13,8 +13,9 @@ resource "google_filestore_instance" "homedirs" {
   }
 
   file_shares {
-    capacity_gb = each.value.capacity_gb
-    name        = "homes"
+    capacity_gb   = each.value.capacity_gb
+    name          = "homes"
+    source_backup = each.value.source_backup
   }
 
   networks {

terraform/gcp/variables.tf

@@ -322,6 +322,7 @@ variable "filestores" {
     name_suffix : optional(string, null),
     capacity_gb : optional(number, 1024),
     tier : optional(string, "BASIC_HDD"),
+    source_backup : optional(string, null),
   }))
   default = {
     "filestore" : {}
@@ -341,6 +342,10 @@ variable "filestores" {
   - tier: Google FileStore service tier to use. Most likely BASIC_HDD
       (for slower home directories, min $204 / month) or BASIC_SSD (for
       faster home directories, min $768 / month). Default: BASIC_HDD.
+  - source_backup: To restore from a backup, this can be set. If a
+      backup has been done from the web console, this must be updated
+      to match retroactively as terraform apply will otherwise lead to
+      a blocked re-creation attempt.
   EOT
 }