✨ #42 Add support for provisioning only a single NAT Gateway (#58)

* 🐛 #47  Fix issue with string vs bool value with enable_nat_gateway input

* ✨ #42 Add support for provisioning only a single NAT Gateway

README.md

@@ -18,6 +18,7 @@ Module Input Variables
 - `enable_dns_hostnames` - should be true if you want to use private DNS within the VPC
 - `enable_dns_support` - should be true if you want to use private DNS within the VPC
 - `enable_nat_gateway` - should be true if you want to provision NAT Gateways
+- `single_nat_gateway` - should be true if you want to provision a single shared NAT Gateway across all of your private networks
 - `enable_s3_endpoint` - should be true if you want to provision an S3 endpoint within the VPC
 - `map_public_ip_on_launch` - should be false if you do not want to auto-assign public IP on launch
 - `private_propagating_vgws` - list of VGWs the private route table should propagate

main.tf

@@ -88,13 +88,13 @@ resource "aws_subnet" "public" {
 
 resource "aws_eip" "nateip" {
   vpc   = true
-  count = "${var.enable_nat_gateway ? length(var.azs) : 0}"
+  count = "${var.enable_nat_gateway ? (var.single_nat_gateway ? 1 : length(var.azs)) : 0}"
 }
 
 resource "aws_nat_gateway" "natgw" {
-  allocation_id = "${element(aws_eip.nateip.*.id, count.index)}"
-  subnet_id     = "${element(aws_subnet.public.*.id, count.index)}"
-  count         = "${var.enable_nat_gateway ? length(var.azs) : 0}"
+  allocation_id = "${element(aws_eip.nateip.*.id, (var.single_nat_gateway ? 0 : count.index))}"
+  subnet_id     = "${element(aws_subnet.public.*.id, (var.single_nat_gateway ? 0 : count.index))}"
+  count         = "${var.enable_nat_gateway ? (var.single_nat_gateway ? 1 : length(var.azs)) : 0}"
 
   depends_on = ["aws_internet_gateway.mod"]
 }

variables.tf

@@ -55,6 +55,11 @@ variable "enable_nat_gateway" {
   default     = false
 }
 
+variable "single_nat_gateway" {
+  description = "should be true if you want to provision a single shared NAT Gateway across all of your private networks"
+  default     = false
+}
+
 variable "enable_s3_endpoint" {
   description = "should be true if you want to provision an S3 endpoint to the VPC"
   default     = false