Change NAT gateway route for the database route table to use the data…

…base route tables instead of the private route tables

examples/database_route_table/README.md

@@ -0,0 +1,3 @@
+# Example: Database Subnet Route Table
+
+Example script for provisioning dedicated database subnets, route table and NAT gateways alongside public and private subnets. It was originally created to resolve an issue where the database route table failed to provision a route for the NAT gateway.

examples/database_route_table/env/Dev.tfvars

@@ -0,0 +1,9 @@
+region = "us-east-1"
+
+# applicaion config
+environment = "Dev"
+vpc_cidr_prefix = "10.120"
+application_name = "DBRouteTableTest"
+
+region_prefix = "VA"
+

examples/database_route_table/main.tf

@@ -0,0 +1,64 @@
+provider "aws" {
+  version = "~> 2.0"
+  region  = var.region
+}
+
+locals {
+  availability_zones = ["${var.region}a", "${var.region}b", "${var.region}c"]
+  private_subnets = ["${var.vpc_cidr_prefix}.0.0/20", "${var.vpc_cidr_prefix}.16.0/20", "${var.vpc_cidr_prefix}.32.0/20"]
+  database_subnets = ["${var.vpc_cidr_prefix}.48.0/24", "${var.vpc_cidr_prefix}.50.0/24"]
+  public_subnets = ["${var.vpc_cidr_prefix}.128.0/20", "${var.vpc_cidr_prefix}.144.0/20", "${var.vpc_cidr_prefix}.160.0/20"]
+}
+
+module "vpc" {
+  #  source  = "terraform-aws-modules/vpc/aws"
+  # version = "2.0"
+  source  = "../.."
+
+  name = "${var.region_prefix}-${var.environment}-${var.application_name}-VPC"
+  cidr = "${var.vpc_cidr_prefix}.0.0/16"
+
+  azs             = local.availability_zones
+  private_subnets = local.private_subnets
+  private_subnet_tags = {
+    Name = "${var.region_prefix}-${var.environment}-${var.application_name}-VPC-PrivateSubnet"
+    Application_Role = "Private Subnet"
+  }
+  public_subnets  = local.public_subnets
+  public_subnet_tags = {
+    Name = "${var.region_prefix}-${var.environment}-${var.application_name}-VPC-PublicSubnet"
+    Application_Role = "Public Subnet"
+  }
+
+  database_subnet_suffix = "Database"
+  database_subnets = local.database_subnets
+  database_subnet_tags = {
+    Name = "${var.region_prefix}-${var.environment}-${var.application_name}-VPC-DatabaseSubnet"
+    Application_Role = "Database Subnet"
+  }
+  create_database_subnet_route_table = true
+  create_database_subnet_group = false
+  create_database_nat_gateway_route = true
+  database_route_table_tags = {
+    Name = "${var.region_prefix}-${var.environment}-${var.application_name}-RT-Database"
+    Application_Role = "Database Route Table"
+  }
+
+  enable_nat_gateway = true
+  # this means we use 1 NAT gateway which is cheaper but not HA if an AZ goes down
+  # we need to determine if multiple NAT gateways are needed (especially in a dev environment)
+  single_nat_gateway = true
+
+  enable_dns_hostnames = true
+  enable_dns_support = true
+  enable_dhcp_options = true
+
+  enable_s3_endpoint = false
+  enable_dynamodb_endpoint = false
+
+  tags = {
+    Name = "${var.region_prefix}-${var.environment}-${var.application_name}-VPC"
+    Application_Role = "Network"
+    Terraform = "true"
+  }
+}

examples/database_route_table/variables.tf

@@ -0,0 +1,19 @@
+variable "region" {
+  description = "The AWS region to create the VPC"
+}
+
+variable "environment" {
+  description = "The name of the environment (ex. Dev)"
+}
+
+variable "vpc_cidr_prefix" {
+  description = "The first two parts of the ipv4 cidr block (ex. 10.120)"
+}
+
+variable "region_prefix" {
+  description = "The abbreviation of the region. i.e. VA, OH, etc."
+}
+
+variable "application_name" {
+  description = "The name of the application to be used for naming resources"
+}

main.tf

@@ -255,7 +255,7 @@ resource "aws_route" "database_internet_gateway" {
 resource "aws_route" "database_nat_gateway" {
   count = var.create_vpc && var.create_database_subnet_route_table && length(var.database_subnets) > 0 && false == var.create_database_internet_gateway_route && var.create_database_nat_gateway_route && var.enable_nat_gateway ? local.nat_gateway_count : 0
 
-  route_table_id         = element(aws_route_table.private.*.id, count.index)
+  route_table_id         = element(aws_route_table.database.*.id, count.index)
   destination_cidr_block = "0.0.0.0/0"
   nat_gateway_id         = element(aws_nat_gateway.this.*.id, count.index)