Added support for existing subnet group and security group

data.tf

@@ -0,0 +1,33 @@
+locals {
+  subnet_tag_name = "Type"
+}
+
+data "aws_vpc" "selected" {
+  filter {
+    name   = "tag:${var.vpc_tag_name}"
+    values = ["${var.vpc_name}${var.vpc_tag_value}"]
+  }
+}
+
+data "aws_subnet_ids" "private" {
+  vpc_id = "${data.aws_vpc.selected.id}"
+
+  filter {
+    name ="tag:${var.vpc_subnet_tag_name}"
+    values = ["${var.vpc_subnet_tag_value}"]
+  }
+
+}
+
+data "aws_security_group" "default" {
+  // This is to use our existing security group for access from the hopper
+  filter {
+    name   = "${var.sg_filter_name}"
+    values = ["${var.sg_filter_value}"]
+  }
+
+  filter {
+    name   = "vpc-id"
+    values = ["${data.aws_vpc.selected.id}"]
+  }
+}

main.tf

@@ -11,6 +11,13 @@ resource "aws_security_group" "redis" {
   }
 }
 
+resource "aws_elasticache_subnet_group" "default" {
+  count  = "${var.enabled == "true" ? 1 : 0}"
+  name        = "subnet-group-${lower(var.cache_identifier)}"
+  description = "Private subnets for the ElastiCache instances:  ${lower(var.cache_identifier)}"
+  subnet_ids  = ["${data.aws_subnet_ids.private.ids}"]
+}
+
 #
 # ElastiCache resources
 #
@@ -22,8 +29,8 @@ resource "aws_elasticache_replication_group" "redis" {
   node_type                     = "${var.instance_type}"
   engine_version                = "${var.engine_version}"
   parameter_group_name          = "${var.parameter_group}"
-  subnet_group_name             = "${var.subnet_group}"
-  security_group_ids            = ["${aws_security_group.redis.id}"]
+  subnet_group_name             = "${var.subnet_group == "" ? aws_elasticache_subnet_group.default.name : var.subnet_group }"
+  security_group_ids            = ["${aws_security_group.redis.id},${data.aws_security_group.default.id}"]
   maintenance_window            = "${var.maintenance_window}"
   notification_topic_arn        = "${var.notification_topic_arn}"
   port                          = "6379"

variables.tf

@@ -8,15 +8,40 @@ variable "environment" {
 
 variable "vpc_id" {}
 
+variable "vpc_name" {
+  description = "Provide vpc name for your region"
+}
+
+variable "vpc_tag_name" {}
+variable "vpc_tag_value" {}
+variable "vpc_subnet_tag_name" {}
+variable "vpc_subnet_tag_value" {}
+
+variable "sg_filter_name" {
+  default = "description"
+}
+
+variable "sg_filter_value" {
+  default = ""
+}
+
+variable "enabled" {
+  description = "Set to false to prevent the module from creating any resources"
+  default     = "true"
+}
+
 variable "cache_identifier" {}
 
 variable "parameter_group" {
   default = "default.redis3.2"
 }
 
-variable "subnet_group" {}
+variable "subnet_group" {
+  default = "cloud-elast-19f609hoj8an"
+}
 
-variable "maintenance_window" {}
+variable "maintenance_window" {
+}
 
 variable "desired_clusters" {
   default = "1"
@@ -34,7 +59,8 @@ variable "automatic_failover_enabled" {
   default = false
 }
 
-variable "notification_topic_arn" {}
+variable "notification_topic_arn" {
+}
 
 variable "alarm_cpu_threshold" {
   default = "75"
@@ -46,5 +72,5 @@ variable "alarm_memory_threshold" {
 }
 
 variable "alarm_actions" {
-  type = "list"
+  type        = "list"
 }