Specify node_group user data via flat variables

Prior to this change, the user data templating variables were nested
under a top level `user_data` module variable, so that when specifying
one piece of it, the default behaviour (specifically the default MIME
type) changed.  There was no precedent in the module for this kind of
behaviour.

This change flattens the user data module variables, making them
independent of each other.  This requires a slightly odd behaviour
around the MIME type, which we have to specify as explicitly `""` (or
alternatively provide a slightly verbose additional module flag) in
order to prevent wrapping the user data in a CloudInit packet.

examples/managed_bottlerocket_node_group/main.tf

@@ -42,14 +42,15 @@ module "eks" {
       public_ip = true
 
       # This section overrides default userdata template to pass bottlerocket
-      # specific user data and pass additional arguments for userdata template rendering
-      user_data = {
-        template_file = "${path.module}/userdata.toml"
-        template_extra_args = {
-          enable_admin_container   = false
-          enable_control_container = true
-          aws_region               = data.aws_region.current.name
-        }
+      # specific user data and pass additional arguments for userdata template rendering.
+      # It also instructs the module to not wrap the user data as cloudinit config, by
+      # indicating that the data has no MIME type.
+      user_data_mime_type     = ""
+      user_data_template_file = "${path.module}/userdata.toml"
+      user_data_template_extra_args = {
+        enable_admin_container   = false
+        enable_control_container = true
+        aws_region               = data.aws_region.current.name
       }
       # example of k8s/kubelet configuration via additional_userdata
       pre_userdata = <<EOT

modules/node_groups/README.md

@@ -55,10 +55,9 @@ The role ARN specified in `var.default_iam_role_arn` will be used by default. In
 | taints | Kubernetes node taints | list(map) | empty |
 | timeouts | A map of timeouts for create/update/delete operations. | `map(string)` | Provider default behavior |
 | update_default_version | Whether or not to set the new launch template version the Default | bool | `true` |
-| user\_data | Alternative `user_data` templating information.  If `user_data` is specified, `user_data.template_file` is required. | `map` (details below) | (see below) |
-| user\_data.mime\_type | Alternative MIME type for the user data. | `string` | `"text/x-shellscript"` |
-| user\_data.template\_extra\_args | Additional variables to make available to the user data template. | `map(string)` | `{}` |
-| user\_data.template\_file | (Required) Alternative template file from which to generate the user data. | `string` | `"${path.module}/templates/userdata.sh.tpl"` |
+| user\_data\_mime\_type | Alternative MIME type for the user data when specifying a cloudinit user data. Explicitly set to the empty string `""` to set the user data as a plain base64 encoded file (such as for use with the Bottlerocket AMI). | `string` | `"text/x-shellscript"` |
+| user\_data\_template\_extra\_args | Additional variables to make available to the user data template. | `map(string)` | `{}` |
+| user\_data\_template\_file | (Required) Alternative template file from which to generate the user data. | `string` | `"${path.module}/templates/userdata.sh.tpl"` |
 | metadata_http_endpoint | The state of the instance metadata service. Requires `create_launch_template` to be `true` | string | `var.workers_group_defaults[metadata_http_endpoint]` |
 | metadata_http_tokens | If session tokens are required. Requires `create_launch_template` to be `true` | string | `var.workers_group_defaults[metadata_http_tokens]` |
 | metadata_http_put_response_hop_limit | The desired HTTP PUT response hop limit for instance metadata requests. Requires `create_launch_template` to be `true` | number | `var.workers_group_defaults[metadata_http_put_response_hop_limit]` |

modules/node_groups/launch_template.tf

@@ -1,15 +1,15 @@
 data "cloudinit_config" "workers_userdata" {
   for_each = {
     for k, v in local.node_groups_expanded : k => v
-    if v["create_launch_template"] && contains(keys(v["user_data"]), "mime_type")
+    if v["create_launch_template"] && len(v["user_data_mime_type"]) > 0
   }
 
   gzip          = false
   base64_encode = true
   boundary      = "//"
 
   part {
-    content_type = each.value["user_data"]["mime_type"]
+    content_type = each.value["user_data_mime_type"]
     content      = local.node_groups_userdata[each.key]
   }
 }

modules/node_groups/locals.tf

@@ -34,10 +34,9 @@ locals {
       metadata_http_tokens                 = var.workers_group_defaults["metadata_http_tokens"]
       metadata_http_put_response_hop_limit = var.workers_group_defaults["metadata_http_put_response_hop_limit"]
       ami_is_eks_optimized                 = true
-      user_data = {
-        mime_type           = "text/x-shellscript"
-        template_extra_args = lookup(var.workers_group_defaults, "userdata_template_file", {})
-        template_file       = lookup(var.workers_group_defaults, "userdata_template_file", "${path.module}/templates/userdata.sh.tpl")
+      user_data_mime_type                  = "text/x-shellscript"
+      user_data_template_extra_args        = lookup(var.workers_group_defaults, "userdata_template_file", {})
+      user_data_template_file              = lookup(var.workers_group_defaults, "userdata_template_file", "${path.module}/templates/userdata.sh.tpl")
       }
     },
     var.node_groups_defaults,
@@ -55,7 +54,7 @@ locals {
   ) }
 
   node_groups_userdata = { for k, v in local.node_groups_expanded : k => templatefile(
-      v["user_data"]["template_file"],
+      v["user_data_template_file"],
       merge(
         {
           cluster_name         = var.cluster_name
@@ -69,7 +68,7 @@ locals {
           capacity_type        = lookup(v, "capacity_type", "ON_DEMAND")
           append_labels        = length(lookup(v, "k8s_labels", {})) > 0 ? ",${join(",", [for key, value in lookup(v, "k8s_labels", {}) : "${key}=${value}"])}" : ""
         },
-        lookup(v["user_data"], "template_extra_args", {})
+        v["user_data_template_extra_args"]
       )
     ) if v["create_launch_template"]
   }