Adding an optional engine flag, so module consumers can use Valkey as an engine

Author: chipbell4

locals.tf

@@ -24,8 +24,6 @@ locals {
 
   automatic_failover_enabled = var.automatic_failover_enabled != null ? var.automatic_failover_enabled : var.nodes >= 2
 
-  engine = "redis"
-
   creator = "terraform"
 
   defaulted_tags = merge(

main.tf

@@ -8,7 +8,7 @@ resource "aws_elasticache_replication_group" "replication_group" {
   auto_minor_version_upgrade  = var.auto_minor_version_upgrade
   automatic_failover_enabled  = local.automatic_failover_enabled
   data_tiering_enabled        = var.data_tiering_enabled
-  engine                      = local.engine
+  engine                      = var.engine
   engine_version              = var.engine_version
   final_snapshot_identifier   = var.final_snapshot_identifier
   global_replication_group_id = var.global_replication_group_id

optional.tf

@@ -22,6 +22,16 @@ variable "auto_minor_version_upgrade" {
   type        = bool
 }
 
+variable "engine" {
+  description = "The engine to use ('valkey' or 'redis')"
+  default     = "redis"
+  type        = string
+  validation {
+    condition     = contains(["redis", "valkey"], var.engine)
+    error_message = "Engine must be 'redis' or 'valkey'"
+  }
+}
+
 variable "engine_version" {
   description = "Version number of the cache engine to be used. If not set, defaults to the latest version. See Describe Cache Engine Versions in the AWS Documentation for supported versions. When engine is redis and the version is 6 or higher, the major and minor version can be set, e.g., 6.2, or the minor version can be unspecified which will use the latest version at creation time, e.g., 6.x. Otherwise, specify the full version desired, e.g., 5.0.6."
   default     = null