feat: Add support for identifier_prefix (#416)

Author: magreenbaum

README.md

@@ -275,6 +275,7 @@ Users have the ability to:
 | <a name="input_iam_database_authentication_enabled"></a> [iam\_database\_authentication\_enabled](#input\_iam\_database\_authentication\_enabled) | Specifies whether or not the mappings of AWS Identity and Access Management (IAM) accounts to database accounts are enabled | `bool` | `false` | no |
 | <a name="input_identifier"></a> [identifier](#input\_identifier) | The name of the RDS instance | `string` | n/a | yes |
 | <a name="input_instance_class"></a> [instance\_class](#input\_instance\_class) | The instance type of the RDS instance | `string` | `null` | no |
+| <a name="input_instance_use_identifier_prefix"></a> [instance\_use\_identifier\_prefix](#input\_instance\_use\_identifier\_prefix) | Determines whether to use `identifier` as is or create a unique identifier beginning with `identifier` as the specified prefix | `bool` | `false` | no |
 | <a name="input_iops"></a> [iops](#input\_iops) | The amount of provisioned IOPS. Setting this implies a storage\_type of 'io1' | `number` | `0` | no |
 | <a name="input_kms_key_id"></a> [kms\_key\_id](#input\_kms\_key\_id) | The ARN for the KMS encryption key. If creating an encrypted replica, set this to the destination KMS ARN. If storage\_encrypted is set to true and kms\_key\_id is not specified the default KMS key created in your account will be used | `string` | `null` | no |
 | <a name="input_license_model"></a> [license\_model](#input\_license\_model) | License model information for this DB instance. Optional, but required for some DB engines, i.e. Oracle SE1 | `string` | `null` | no |

examples/complete-postgres/main.tf

@@ -124,7 +124,8 @@ module "db" {
 module "db_default" {
   source = "../../"
 
-  identifier = "${local.name}-default"
+  identifier                     = "${local.name}-default"
+  instance_use_identifier_prefix = true
 
   create_db_option_group    = false
   create_db_parameter_group = false

main.tf

@@ -69,8 +69,9 @@ module "db_option_group" {
 module "db_instance" {
   source = "./modules/db_instance"
 
-  create     = local.create_db_instance
-  identifier = var.identifier
+  create                = local.create_db_instance
+  identifier            = var.identifier
+  use_identifier_prefix = var.instance_use_identifier_prefix
 
   engine            = var.engine
   engine_version    = var.engine_version

modules/db_instance/README.md

@@ -93,6 +93,7 @@ No modules.
 | <a name="input_tags"></a> [tags](#input\_tags) | A mapping of tags to assign to all resources | `map(string)` | `{}` | no |
 | <a name="input_timeouts"></a> [timeouts](#input\_timeouts) | Updated Terraform resource management timeouts. Applies to `aws_db_instance` in particular to permit resource management times | `map(string)` | `{}` | no |
 | <a name="input_timezone"></a> [timezone](#input\_timezone) | Time zone of the DB instance. timezone is currently only supported by Microsoft SQL Server. The timezone can only be set on creation. See MSSQL User Guide for more information. | `string` | `null` | no |
+| <a name="input_use_identifier_prefix"></a> [use\_identifier\_prefix](#input\_use\_identifier\_prefix) | Determines whether to use `identifier` as is or create a unique identifier beginning with `identifier` as the specified prefix | `bool` | `false` | no |
 | <a name="input_username"></a> [username](#input\_username) | Username for the master DB user | `string` | `null` | no |
 | <a name="input_vpc_security_group_ids"></a> [vpc\_security\_group\_ids](#input\_vpc\_security\_group\_ids) | List of VPC security groups to associate | `list(string)` | `[]` | no |
 

modules/db_instance/main.tf

@@ -3,6 +3,9 @@ locals {
 
   final_snapshot_identifier = var.skip_final_snapshot ? null : "${var.final_snapshot_identifier_prefix}-${var.identifier}-${try(random_id.snapshot_identifier[0].hex, "")}"
 
+  identifier        = var.use_identifier_prefix ? null : var.identifier
+  identifier_prefix = var.use_identifier_prefix ? "${var.identifier}-" : null
+
   # Replicas will use source metadata
   username       = var.replicate_source_db != null ? null : var.username
   password       = var.replicate_source_db != null ? null : var.password
@@ -26,7 +29,8 @@ resource "random_id" "snapshot_identifier" {
 resource "aws_db_instance" "this" {
   count = var.create ? 1 : 0
 
-  identifier = var.identifier
+  identifier        = local.identifier
+  identifier_prefix = local.identifier_prefix
 
   engine            = local.engine
   engine_version    = local.engine_version

modules/db_instance/variables.tf

@@ -9,6 +9,12 @@ variable "identifier" {
   type        = string
 }
 
+variable "use_identifier_prefix" {
+  description = "Determines whether to use `identifier` as is or create a unique identifier beginning with `identifier` as the specified prefix"
+  type        = bool
+  default     = false
+}
+
 variable "allocated_storage" {
   description = "The allocated storage in gigabytes"
   type        = string

variables.tf

@@ -3,6 +3,12 @@ variable "identifier" {
   type        = string
 }
 
+variable "instance_use_identifier_prefix" {
+  description = "Determines whether to use `identifier` as is or create a unique identifier beginning with `identifier` as the specified prefix"
+  type        = bool
+  default     = false
+}
+
 variable "allocated_storage" {
   description = "The allocated storage in gigabytes"
   type        = string