feat: Add single_nat_gateway_subnet_index to choose NAT Gateway public subnet

README.md

@@ -579,6 +579,7 @@ No modules.
 | <a name="input_reuse_nat_ips"></a> [reuse\_nat\_ips](#input\_reuse\_nat\_ips) | Should be true if you don't want EIPs to be created for your NAT Gateways and will instead pass them in via the 'external\_nat\_ip\_ids' variable | `bool` | `false` | no |
 | <a name="input_secondary_cidr_blocks"></a> [secondary\_cidr\_blocks](#input\_secondary\_cidr\_blocks) | List of secondary CIDR blocks to associate with the VPC to extend the IP Address pool | `list(string)` | `[]` | no |
 | <a name="input_single_nat_gateway"></a> [single\_nat\_gateway](#input\_single\_nat\_gateway) | Should be true if you want to provision a single shared NAT Gateway across all of your private networks | `bool` | `false` | no |
+| <a name="input_single_nat_gateway_subnet_index"></a> [single\_nat\_gateway\_subnet\_index](#input\_single\_nat\_gateway\_subnet\_index) | The index of the public subnet used for the NAT Gateway. Only used when `single_nat_gateway` is true | `number` | `0` | no |
 | <a name="input_tags"></a> [tags](#input\_tags) | A map of tags to add to all resources | `map(string)` | `{}` | no |
 | <a name="input_use_ipam_pool"></a> [use\_ipam\_pool](#input\_use\_ipam\_pool) | Determines whether IPAM pool is used for CIDR allocation | `bool` | `false` | no |
 | <a name="input_vpc_flow_log_iam_policy_name"></a> [vpc\_flow\_log\_iam\_policy\_name](#input\_vpc\_flow\_log\_iam\_policy\_name) | Name of the IAM policy | `string` | `"vpc-flow-log-to-cloudwatch"` | no |

examples/complete/main.tf

@@ -54,6 +54,8 @@ module "vpc" {
   enable_nat_gateway = true
   single_nat_gateway = true
 
+  single_nat_gateway_subnet_index = 1
+
   customer_gateways = {
     IP1 = {
       bgp_asn     = 65112

main.tf

@@ -1084,14 +1084,14 @@ resource "aws_nat_gateway" "this" {
   )
   subnet_id = element(
     aws_subnet.public[*].id,
-    var.single_nat_gateway ? 0 : count.index,
+    var.single_nat_gateway ? var.single_nat_gateway_subnet_index : count.index,
   )
 
   tags = merge(
     {
-      "Name" = format(
+      "Name" = var.single_nat_gateway ? var.name : format(
         "${var.name}-%s",
-        element(var.azs, var.single_nat_gateway ? 0 : count.index),
+        element(var.azs, count.index),
       )
     },
     var.tags,

variables.tf

@@ -1210,6 +1210,12 @@ variable "single_nat_gateway" {
   default     = false
 }
 
+variable "single_nat_gateway_subnet_index" {
+  description = "The index of the public subnet used for the NAT Gateway. Only used when `single_nat_gateway` is true"
+  type        = number
+  default     = 0
+}
+
 variable "one_nat_gateway_per_az" {
   description = "Should be true if you want only one NAT Gateway per availability zone. Requires `var.azs` to be set, and the number of `public_subnets` created to be greater than or equal to the number of availability zones specified in `var.azs`"
   type        = bool