feat: Add support for multiple route tables to public and intra subnets (#1051)

Co-authored-by: Kevin Snyder <kevinsnyder@Kevins-Raft-MacBook-Pro.local>
Co-authored-by: Bryant Biggs <bryantbiggs@gmail.com>

.pre-commit-config.yaml

 repos:
   - repo: https://github.com/antonbabenko/pre-commit-terraform
-    rev: v1.88.0
+    rev: v1.89.0
     hooks:
       - id: terraform_fmt
       - id: terraform_docs
@@ -24,7 +24,7 @@ repos:
           - '--args=--only=terraform_unused_required_providers'
       - id: terraform_validate
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v4.5.0
+    rev: v4.6.0
     hooks:
       - id: check-merge-conflict
       - id: end-of-file-fixer

README.md

@@ -369,6 +369,8 @@ No modules.
 | <a name="input_create_flow_log_cloudwatch_iam_role"></a> [create\_flow\_log\_cloudwatch\_iam\_role](#input\_create\_flow\_log\_cloudwatch\_iam\_role) | Whether to create IAM role for VPC Flow Logs | `bool` | `false` | no |
 | <a name="input_create_flow_log_cloudwatch_log_group"></a> [create\_flow\_log\_cloudwatch\_log\_group](#input\_create\_flow\_log\_cloudwatch\_log\_group) | Whether to create CloudWatch log group for VPC Flow Logs | `bool` | `false` | no |
 | <a name="input_create_igw"></a> [create\_igw](#input\_create\_igw) | Controls if an Internet Gateway is created for public subnets and the related routes that connect them | `bool` | `true` | no |
+| <a name="input_create_multiple_intra_route_tables"></a> [create\_multiple\_intra\_route\_tables](#input\_create\_multiple\_intra\_route\_tables) | Indicates whether to create a separate route table for each intra subnet. Default: `false` | `bool` | `false` | no |
+| <a name="input_create_multiple_public_route_tables"></a> [create\_multiple\_public\_route\_tables](#input\_create\_multiple\_public\_route\_tables) | Indicates whether to create a separate route table for each public subnet. Default: `false` | `bool` | `false` | no |
 | <a name="input_create_redshift_subnet_group"></a> [create\_redshift\_subnet\_group](#input\_create\_redshift\_subnet\_group) | Controls if redshift subnet group should be created | `bool` | `true` | no |
 | <a name="input_create_redshift_subnet_route_table"></a> [create\_redshift\_subnet\_route\_table](#input\_create\_redshift\_subnet\_route\_table) | Controls if separate route table for redshift should be created | `bool` | `false` | no |
 | <a name="input_create_vpc"></a> [create\_vpc](#input\_create\_vpc) | Controls if VPC should be created (it affects almost all resources) | `bool` | `true` | no |

main.tf

@@ -123,13 +123,22 @@ resource "aws_subnet" "public" {
   )
 }
 
+locals {
+  num_public_route_tables = var.create_multiple_public_route_tables ? local.len_public_subnets : 1
+}
+
 resource "aws_route_table" "public" {
-  count = local.create_public_subnets ? 1 : 0
+  count = local.create_public_subnets ? local.num_public_route_tables : 0
 
   vpc_id = local.vpc_id
 
   tags = merge(
-    { "Name" = "${var.name}-${var.public_subnet_suffix}" },
+    {
+      "Name" = var.create_multiple_public_route_tables ? format(
+        "${var.name}-${var.public_subnet_suffix}-%s",
+        element(var.azs, count.index),
+      ) : "${var.name}-${var.public_subnet_suffix}"
+    },
     var.tags,
     var.public_route_table_tags,
   )
@@ -139,7 +148,7 @@ resource "aws_route_table_association" "public" {
   count = local.create_public_subnets ? local.len_public_subnets : 0
 
   subnet_id      = element(aws_subnet.public[*].id, count.index)
-  route_table_id = aws_route_table.public[0].id
+  route_table_id = element(aws_route_table.public[*].id, var.create_multiple_public_route_tables ? count.index : 0)
 }
 
 resource "aws_route" "public_internet_gateway" {
@@ -816,13 +825,22 @@ resource "aws_subnet" "intra" {
   )
 }
 
+locals {
+  num_intra_route_tables = var.create_multiple_intra_route_tables ? local.len_intra_subnets : 1
+}
+
 resource "aws_route_table" "intra" {
-  count = local.create_intra_subnets ? 1 : 0
+  count = local.create_intra_subnets ? local.num_intra_route_tables : 0
 
   vpc_id = local.vpc_id
 
   tags = merge(
-    { "Name" = "${var.name}-${var.intra_subnet_suffix}" },
+    {
+      "Name" = var.create_multiple_intra_route_tables ? format(
+        "${var.name}-${var.intra_subnet_suffix}-%s",
+        element(var.azs, count.index),
+      ) : "${var.name}-${var.intra_subnet_suffix}"
+    },
     var.tags,
     var.intra_route_table_tags,
   )
@@ -832,7 +850,7 @@ resource "aws_route_table_association" "intra" {
   count = local.create_intra_subnets ? local.len_intra_subnets : 0
 
   subnet_id      = element(aws_subnet.intra[*].id, count.index)
-  route_table_id = element(aws_route_table.intra[*].id, 0)
+  route_table_id = element(aws_route_table.intra[*].id, var.create_multiple_intra_route_tables ? count.index : 0)
 }
 
 ################################################################################

variables.tf

@@ -196,6 +196,12 @@ variable "public_subnet_enable_resource_name_dns_a_record_on_launch" {
   default     = false
 }
 
+variable "create_multiple_public_route_tables" {
+  description = "Indicates whether to create a separate route table for each public subnet. Default: `false`"
+  type        = bool
+  default     = false
+}
+
 variable "public_subnet_ipv6_prefixes" {
   description = "Assigns IPv6 public subnet id based on the Amazon provided /56 prefix base 10 integer (0-256). Must be of equal length to the corresponding IPv4 subnet list"
   type        = list(string)
@@ -914,6 +920,12 @@ variable "intra_subnet_enable_resource_name_dns_a_record_on_launch" {
   default     = false
 }
 
+variable "create_multiple_intra_route_tables" {
+  description = "Indicates whether to create a separate route table for each intra subnet. Default: `false`"
+  type        = bool
+  default     = false
+}
+
 variable "intra_subnet_ipv6_prefixes" {
   description = "Assigns IPv6 intra subnet id based on the Amazon provided /56 prefix base 10 integer (0-256). Must be of equal length to the corresponding IPv4 subnet list"
   type        = list(string)