feat: Add support for Valkey engine (#249)

This change allows setting the `engine` variable, to allow using Valkey
as the cache engine.

No breaking changes are expected, as the default value for the `engine`
variable is set to `redis`. Also, the minimum AWS provider version is
not changed as using Redis does not require using a newer provider.

README.md

@@ -241,10 +241,11 @@ Available targets:
 | <a name="input_egress_cidr_blocks"></a> [egress\_cidr\_blocks](#input\_egress\_cidr\_blocks) | DEPRECATED: Use `allow_all_egress` and `additional_security_group_rules` instead.<br/>Historical description: Outbound traffic address.<br/>Historical default: ["0.0.0.0/0"] | `list(any)` | `null` | no |
 | <a name="input_elasticache_subnet_group_name"></a> [elasticache\_subnet\_group\_name](#input\_elasticache\_subnet\_group\_name) | Subnet group name for the ElastiCache instance | `string` | `""` | no |
 | <a name="input_enabled"></a> [enabled](#input\_enabled) | Set to false to prevent the module from creating any resources | `bool` | `null` | no |
-| <a name="input_engine_version"></a> [engine\_version](#input\_engine\_version) | Redis engine version | `string` | `"4.0.10"` | no |
+| <a name="input_engine"></a> [engine](#input\_engine) | Name of the cache engine | `string` | `"redis"` | no |
+| <a name="input_engine_version"></a> [engine\_version](#input\_engine\_version) | Version number of the cache engine | `string` | `"4.0.10"` | no |
 | <a name="input_environment"></a> [environment](#input\_environment) | ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT' | `string` | `null` | no |
 | <a name="input_existing_security_groups"></a> [existing\_security\_groups](#input\_existing\_security\_groups) | DEPRECATED: Use `associated_security_group_ids` instead.<br/>Historical description: List of existing Security Group IDs to place the cluster into.<br/>Set `use_existing_security_groups` to `true` to enable using `existing_security_groups` as Security Groups for the cluster. | `list(string)` | `[]` | no |
-| <a name="input_family"></a> [family](#input\_family) | Redis family | `string` | `"redis4.0"` | no |
+| <a name="input_family"></a> [family](#input\_family) | The family of the ElastiCache parameter group | `string` | `"redis4.0"` | no |
 | <a name="input_final_snapshot_identifier"></a> [final\_snapshot\_identifier](#input\_final\_snapshot\_identifier) | The name of your final node group (shard) snapshot. ElastiCache creates the snapshot from the primary node in the cluster. If omitted, no final snapshot will be made. | `string` | `null` | no |
 | <a name="input_id_length_limit"></a> [id\_length\_limit](#input\_id\_length\_limit) | Limit `id` to this many characters (minimum 6).<br/>Set to `0` for unlimited length.<br/>Set to `null` for keep the existing setting, which defaults to `0`.<br/>Does not affect `id_full`. | `number` | `null` | no |
 | <a name="input_inline_rules_enabled"></a> [inline\_rules\_enabled](#input\_inline\_rules\_enabled) | NOT RECOMMENDED. Create rules "inline" instead of as separate `aws_security_group_rule` resources.<br/>See [#20046](https://github.com/hashicorp/terraform-provider-aws/issues/20046) for one of several issues with inline rules.<br/>See [this post](https://github.com/hashicorp/terraform-provider-aws/pull/9032#issuecomment-639545250) for details on the difference between inline rules and rule resources. | `bool` | `false` | no |
@@ -265,7 +266,7 @@ Available targets:
 | <a name="input_parameter"></a> [parameter](#input\_parameter) | A list of Redis parameters to apply. Note that parameters may differ from one Redis family to another | <pre>list(object({<br/>    name  = string<br/>    value = string<br/>  }))</pre> | `[]` | no |
 | <a name="input_parameter_group_description"></a> [parameter\_group\_description](#input\_parameter\_group\_description) | Managed by Terraform | `string` | `null` | no |
 | <a name="input_parameter_group_name"></a> [parameter\_group\_name](#input\_parameter\_group\_name) | Override the default parameter group name | `string` | `null` | no |
-| <a name="input_port"></a> [port](#input\_port) | Redis port | `number` | `6379` | no |
+| <a name="input_port"></a> [port](#input\_port) | Port number on which the cache nodes will accept connections | `number` | `6379` | no |
 | <a name="input_preserve_security_group_id"></a> [preserve\_security\_group\_id](#input\_preserve\_security\_group\_id) | When `false` and `create_before_destroy` is `true`, changes to security group rules<br/>cause a new security group to be created with the new rules, and the existing security group is then<br/>replaced with the new one, eliminating any service interruption.<br/>When `true` or when changing the value (from `false` to `true` or from `true` to `false`),<br/>existing security group rules will be deleted before new ones are created, resulting in a service interruption,<br/>but preserving the security group itself.<br/>**NOTE:** Setting this to `true` does not guarantee the security group will never be replaced,<br/>it only keeps changes to the security group rules from triggering a replacement.<br/>See the README for further discussion. | `bool` | `false` | no |
 | <a name="input_regex_replace_chars"></a> [regex\_replace\_chars](#input\_regex\_replace\_chars) | Terraform regular expression (regex) string.<br/>Characters matching the regex will be removed from the ID elements.<br/>If not set, `"/[^a-zA-Z0-9-]/"` is used to remove all characters other than hyphens, letters and digits. | `string` | `null` | no |
 | <a name="input_replication_group_id"></a> [replication\_group\_id](#input\_replication\_group\_id) | Replication group ID with the following constraints: <br/>A name must contain from 1 to 20 alphanumeric characters or hyphens. <br/> The first character must be a letter. <br/> A name cannot end with a hyphen or contain two consecutive hyphens. | `string` | `""` | no |

docs/terraform.md

@@ -69,10 +69,11 @@
 | <a name="input_egress_cidr_blocks"></a> [egress\_cidr\_blocks](#input\_egress\_cidr\_blocks) | DEPRECATED: Use `allow_all_egress` and `additional_security_group_rules` instead.<br/>Historical description: Outbound traffic address.<br/>Historical default: ["0.0.0.0/0"] | `list(any)` | `null` | no |
 | <a name="input_elasticache_subnet_group_name"></a> [elasticache\_subnet\_group\_name](#input\_elasticache\_subnet\_group\_name) | Subnet group name for the ElastiCache instance | `string` | `""` | no |
 | <a name="input_enabled"></a> [enabled](#input\_enabled) | Set to false to prevent the module from creating any resources | `bool` | `null` | no |
-| <a name="input_engine_version"></a> [engine\_version](#input\_engine\_version) | Redis engine version | `string` | `"4.0.10"` | no |
+| <a name="input_engine"></a> [engine](#input\_engine) | Name of the cache engine | `string` | `"redis"` | no |
+| <a name="input_engine_version"></a> [engine\_version](#input\_engine\_version) | Version number of the cache engine | `string` | `"4.0.10"` | no |
 | <a name="input_environment"></a> [environment](#input\_environment) | ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT' | `string` | `null` | no |
 | <a name="input_existing_security_groups"></a> [existing\_security\_groups](#input\_existing\_security\_groups) | DEPRECATED: Use `associated_security_group_ids` instead.<br/>Historical description: List of existing Security Group IDs to place the cluster into.<br/>Set `use_existing_security_groups` to `true` to enable using `existing_security_groups` as Security Groups for the cluster. | `list(string)` | `[]` | no |
-| <a name="input_family"></a> [family](#input\_family) | Redis family | `string` | `"redis4.0"` | no |
+| <a name="input_family"></a> [family](#input\_family) | The family of the ElastiCache parameter group | `string` | `"redis4.0"` | no |
 | <a name="input_final_snapshot_identifier"></a> [final\_snapshot\_identifier](#input\_final\_snapshot\_identifier) | The name of your final node group (shard) snapshot. ElastiCache creates the snapshot from the primary node in the cluster. If omitted, no final snapshot will be made. | `string` | `null` | no |
 | <a name="input_id_length_limit"></a> [id\_length\_limit](#input\_id\_length\_limit) | Limit `id` to this many characters (minimum 6).<br/>Set to `0` for unlimited length.<br/>Set to `null` for keep the existing setting, which defaults to `0`.<br/>Does not affect `id_full`. | `number` | `null` | no |
 | <a name="input_inline_rules_enabled"></a> [inline\_rules\_enabled](#input\_inline\_rules\_enabled) | NOT RECOMMENDED. Create rules "inline" instead of as separate `aws_security_group_rule` resources.<br/>See [#20046](https://github.com/hashicorp/terraform-provider-aws/issues/20046) for one of several issues with inline rules.<br/>See [this post](https://github.com/hashicorp/terraform-provider-aws/pull/9032#issuecomment-639545250) for details on the difference between inline rules and rule resources. | `bool` | `false` | no |
@@ -93,7 +94,7 @@
 | <a name="input_parameter"></a> [parameter](#input\_parameter) | A list of Redis parameters to apply. Note that parameters may differ from one Redis family to another | <pre>list(object({<br/>    name  = string<br/>    value = string<br/>  }))</pre> | `[]` | no |
 | <a name="input_parameter_group_description"></a> [parameter\_group\_description](#input\_parameter\_group\_description) | Managed by Terraform | `string` | `null` | no |
 | <a name="input_parameter_group_name"></a> [parameter\_group\_name](#input\_parameter\_group\_name) | Override the default parameter group name | `string` | `null` | no |
-| <a name="input_port"></a> [port](#input\_port) | Redis port | `number` | `6379` | no |
+| <a name="input_port"></a> [port](#input\_port) | Port number on which the cache nodes will accept connections | `number` | `6379` | no |
 | <a name="input_preserve_security_group_id"></a> [preserve\_security\_group\_id](#input\_preserve\_security\_group\_id) | When `false` and `create_before_destroy` is `true`, changes to security group rules<br/>cause a new security group to be created with the new rules, and the existing security group is then<br/>replaced with the new one, eliminating any service interruption.<br/>When `true` or when changing the value (from `false` to `true` or from `true` to `false`),<br/>existing security group rules will be deleted before new ones are created, resulting in a service interruption,<br/>but preserving the security group itself.<br/>**NOTE:** Setting this to `true` does not guarantee the security group will never be replaced,<br/>it only keeps changes to the security group rules from triggering a replacement.<br/>See the README for further discussion. | `bool` | `false` | no |
 | <a name="input_regex_replace_chars"></a> [regex\_replace\_chars](#input\_regex\_replace\_chars) | Terraform regular expression (regex) string.<br/>Characters matching the regex will be removed from the ID elements.<br/>If not set, `"/[^a-zA-Z0-9-]/"` is used to remove all characters other than hyphens, letters and digits. | `string` | `null` | no |
 | <a name="input_replication_group_id"></a> [replication\_group\_id](#input\_replication\_group\_id) | Replication group ID with the following constraints: <br/>A name must contain from 1 to 20 alphanumeric characters or hyphens. <br/> The first character must be a letter. <br/> A name cannot end with a hyphen or contain two consecutive hyphens. | `string` | `""` | no |

main.tf

@@ -176,6 +176,7 @@ resource "aws_elasticache_replication_group" "default" {
   security_group_ids         = local.create_security_group ? concat(local.associated_security_group_ids, [module.aws_security_group.id]) : local.associated_security_group_ids
   maintenance_window         = var.maintenance_window
   notification_topic_arn     = var.notification_topic_arn
+  engine                     = var.engine
   engine_version             = var.engine_version
   at_rest_encryption_enabled = var.at_rest_encryption_enabled
   transit_encryption_enabled = var.transit_encryption_enabled
@@ -221,12 +222,12 @@ resource "aws_elasticache_replication_group" "default" {
   ]
 }
 
-# Create a Serverless Redis instance
+# Create a Serverless Redis/Valkey instance
 resource "aws_elasticache_serverless_cache" "default" {
   count = local.create_serverless_instance ? 1 : 0
 
   name   = var.replication_group_id == "" ? module.this.id : var.replication_group_id
-  engine = "redis"
+  engine = var.engine
 
   kms_key_id         = var.at_rest_encryption_enabled ? var.kms_key_id : null
   subnet_ids         = var.subnets

variables.tf

@@ -36,7 +36,7 @@ variable "cluster_size" {
 variable "port" {
   type        = number
   default     = 6379
-  description = "Redis port"
+  description = "Port number on which the cache nodes will accept connections"
 }
 
 variable "instance_type" {
@@ -48,7 +48,7 @@ variable "instance_type" {
 variable "family" {
   type        = string
   default     = "redis4.0"
-  description = "Redis family"
+  description = "The family of the ElastiCache parameter group"
 }
 
 variable "parameter" {
@@ -60,10 +60,16 @@ variable "parameter" {
   description = "A list of Redis parameters to apply. Note that parameters may differ from one Redis family to another"
 }
 
+variable "engine" {
+  type        = string
+  default     = "redis"
+  description = "Name of the cache engine"
+}
+
 variable "engine_version" {
   type        = string
   default     = "4.0.10"
-  description = "Redis engine version"
+  description = "Version number of the cache engine"
 }
 
 variable "at_rest_encryption_enabled" {