Adding "intra subnets" as a class

main.tf

@@ -192,6 +192,19 @@ resource "aws_elasticache_subnet_group" "elasticache" {
   subnet_ids  = ["${aws_subnet.elasticache.*.id}"]
 }
 
+#####################################################
+# infra subnets - private subnet with no NAT gateway
+#####################################################
+resource "aws_subnet" "infra" {
+  count = "${var.create_vpc && length(var.infra_subnets) > 0 ? length(var.infra_subnets) : 0}"
+
+  vpc_id            = "${aws_vpc.this.id}"
+  cidr_block        = "${var.infra_subnets[count.index]}"
+  availability_zone = "${element(var.azs, count.index)}"
+
+  tags = "${merge(var.tags, var.infra_subnet_tags, map("Name", format("%s-infra-%s", var.name, element(var.azs, count.index))))}"
+}
+
 ##############
 # NAT Gateway
 ##############
@@ -329,6 +342,13 @@ resource "aws_route_table_association" "elasticache" {
   route_table_id = "${element(aws_route_table.private.*.id, (var.single_nat_gateway ? 0 : count.index))}"
 }
 
+resource "aws_route_table_association" "infra" {
+  count = "${var.create_vpc && length(var.infra_subnets) > 0 ? length(var.infra_subnets) : 0}"
+
+  subnet_id      = "${element(aws_subnet.infra.*.id, count.index)}"
+  route_table_id = "${element(aws_route_table.private.*.id, (var.single_nat_gateway ? 0 : count.index))}"
+}
+
 resource "aws_route_table_association" "public" {
   count = "${var.create_vpc && length(var.public_subnets) > 0 ? length(var.public_subnets) : 0}"
 

outputs.tf

@@ -120,6 +120,16 @@ output "elasticache_subnets_cidr_blocks" {
   value       = ["${aws_subnet.elasticache.*.cidr_block}"]
 }
 
+output "infra_subnets" {
+  description = "List of IDs of infra subnets"
+  value       = ["${aws_subnet.infra.*.id}"]
+}
+
+output "infra_subnets_cidr_blocks" {
+  description = "List of cidr_blocks of infra subnets"
+  value       = ["${aws_subnet.infra.*.cidr_block}"]
+}
+
 output "elasticache_subnet_group" {
   description = "ID of elasticache subnet group"
   value       = "${element(concat(aws_elasticache_subnet_group.elasticache.*.id, list("")), 0)}"

variables.tf

@@ -46,6 +46,12 @@ variable "elasticache_subnets" {
   default     = []
 }
 
+variable "infra_subnets" {
+  type        = "list"
+  description = "A list of infra subnets"
+  default     = []
+}
+
 variable "create_database_subnet_group" {
   description = "Controls if database subnet group should be created"
   default     = true
@@ -177,6 +183,11 @@ variable "elasticache_subnet_tags" {
   default     = {}
 }
 
+variable "infra_subnet_tags" {
+  description = "Additional tags for the infra subnets"
+  default     = {}
+}
+
 variable "dhcp_options_tags" {
   description = "Additional tags for the DHCP option set"
   default     = {}