data/aws/vpc: Lay the groundwork for bring-your-own VPC/subnets

data/data/aws/main.tf

@@ -75,9 +75,13 @@ module "dns" {
 module "vpc" {
   source = "./vpc"
 
-  cidr_block = var.machine_cidr
-  cluster_id = var.cluster_id
-  region     = var.aws_region
+  cidr_block      = var.machine_cidr
+  cluster_id      = var.cluster_id
+  region          = var.aws_region
+  vpc             = var.aws_vpc
+  public_subnets  = var.aws_public_subnets
+  private_subnets = var.aws_private_subnets
+
   availability_zones = distinct(
     concat(
       var.aws_master_availability_zones,

data/data/aws/variables-aws.tf

@@ -69,3 +69,20 @@ variable "aws_worker_availability_zones" {
   description = "The availability zones to provision for workers.  Worker instances are created by the machine-API operator, but this variable controls their supporting infrastructure (subnets, routing, etc.)."
 }
 
+variable "aws_vpc" {
+  type = string
+  default = null
+  description = "(optional) An existing network (VPC ID) into which the cluster should be installed."
+}
+
+variable "aws_public_subnets" {
+  type = list(string)
+  default = null
+  description = "(optional) Existing public subnets into which the cluster should be installed."
+}
+
+variable "aws_private_subnets" {
+  type = list(string)
+  default = null
+  description = "(optional) Existing private subnets into which the cluster should be installed."
+}

data/data/aws/vpc/common.tf

@@ -1,16 +1,21 @@
 # Canonical internal state definitions for this module.
 # read only: only locals and data source definitions allowed. No resources or module blocks in this file
 
-// Only reference data sources which are guaranteed to exist at any time (above) in this locals{} block
-locals {
-  private_subnet_ids = aws_subnet.private_subnet.*.id
-  public_subnet_ids  = aws_subnet.public_subnet.*.id
-}
-
 # all data sources should be input variable-agnostic and used as canonical source for querying "state of resources" and building outputs
 # (ie: we don't want "aws.new_vpc" and "data.aws_vpc.cluster_vpc", just "data.aws_vpc.cluster_vpc" used everwhere).
 
 data "aws_vpc" "cluster_vpc" {
-  id = aws_vpc.new_vpc.id
+  id = var.vpc == null ? aws_vpc.new_vpc[0].id : var.vpc
 }
 
+data "aws_subnet" "public" {
+  count = var.public_subnets == null ? length(var.availability_zones) : length(var.public_subnets)
+
+  id = var.public_subnets == null ? aws_subnet.public_subnet[count.index].id : var.public_subnets[count.index]
+}
+
+data "aws_subnet" "private" {
+  count = var.private_subnets == null ? length(var.availability_zones) : length(var.private_subnets)
+
+  id = var.private_subnets == null ? aws_subnet.private_subnet[count.index].id : var.private_subnets[count.index]
+}

data/data/aws/vpc/master-elb.tf

@@ -1,7 +1,7 @@
 resource "aws_lb" "api_internal" {
   name                             = "${var.cluster_id}-int"
   load_balancer_type               = "network"
-  subnets                          = local.private_subnet_ids
+  subnets                          = data.aws_subnet.private.*.id
   internal                         = true
   enable_cross_zone_load_balancing = true
   idle_timeout                     = 3600
@@ -23,7 +23,7 @@ resource "aws_lb" "api_internal" {
 resource "aws_lb" "api_external" {
   name                             = "${var.cluster_id}-ext"
   load_balancer_type               = "network"
-  subnets                          = local.public_subnet_ids
+  subnets                          = data.aws_subnet.public.*.id
   internal                         = false
   enable_cross_zone_load_balancing = true
   idle_timeout                     = 3600

data/data/aws/vpc/outputs.tf

@@ -3,19 +3,19 @@ output "vpc_id" {
 }
 
 output "az_to_private_subnet_id" {
-  value = zipmap(var.availability_zones, local.private_subnet_ids)
+  value = zipmap(data.aws_subnet.private.*.availability_zone, data.aws_subnet.private.*.id)
 }
 
 output "az_to_public_subnet_id" {
-  value = zipmap(var.availability_zones, local.public_subnet_ids)
+  value = zipmap(data.aws_subnet.public.*.availability_zone, data.aws_subnet.public.*.id)
 }
 
 output "public_subnet_ids" {
-  value = local.public_subnet_ids
+  value = data.aws_subnet.public.*.id
 }
 
 output "private_subnet_ids" {
-  value = local.private_subnet_ids
+  value = data.aws_subnet.private.*.id
 }
 
 output "master_sg_id" {

data/data/aws/vpc/variables.tf

@@ -32,3 +32,17 @@ variable "tags" {
   description = "AWS tags to be applied to created resources."
 }
 
+variable "vpc" {
+  type        = string
+  description = "An existing network (VPC ID) into which the cluster should be installed."
+}
+
+variable "public_subnets" {
+  type        = list(string)
+  description = "Existing public subnets into which the cluster should be installed."
+}
+
+variable "private_subnets" {
+  type        = list(string)
+  description = "Existing private subnets into which the cluster should be installed."
+}

data/data/aws/vpc/vpc-private.tf

@@ -1,5 +1,6 @@
 resource "aws_route_table" "private_routes" {
-  count  = length(var.availability_zones)
+  count = var.private_subnets == null ? length(var.availability_zones) : 0
+
   vpc_id = data.aws_vpc.cluster_vpc.id
 
   tags = merge(
@@ -11,7 +12,8 @@ resource "aws_route_table" "private_routes" {
 }
 
 resource "aws_route" "to_nat_gw" {
-  count                  = length(var.availability_zones)
+  count = var.private_subnets == null ? length(var.availability_zones) : 0
+
   route_table_id         = aws_route_table.private_routes[count.index].id
   destination_cidr_block = "0.0.0.0/0"
   nat_gateway_id         = element(aws_nat_gateway.nat_gw.*.id, count.index)
@@ -23,7 +25,7 @@ resource "aws_route" "to_nat_gw" {
 }
 
 resource "aws_subnet" "private_subnet" {
-  count = length(var.availability_zones)
+  count = var.private_subnets == null ? length(var.availability_zones) : 0
 
   vpc_id = data.aws_vpc.cluster_vpc.id
 
@@ -41,8 +43,8 @@ resource "aws_subnet" "private_subnet" {
 }
 
 resource "aws_route_table_association" "private_routing" {
-  count          = length(var.availability_zones)
+  count = var.private_subnets == null ? length(var.availability_zones) : 0
+
   route_table_id = aws_route_table.private_routes[count.index].id
   subnet_id      = aws_subnet.private_subnet[count.index].id
 }
-

data/data/aws/vpc/vpc-public.tf

@@ -1,4 +1,6 @@
 resource "aws_internet_gateway" "igw" {
+  count = var.vpc == null ? 1 : 0
+
   vpc_id = data.aws_vpc.cluster_vpc.id
 
   tags = merge(
@@ -10,6 +12,8 @@ resource "aws_internet_gateway" "igw" {
 }
 
 resource "aws_route_table" "default" {
+  count = var.vpc == null ? 1 : 0
+
   vpc_id = data.aws_vpc.cluster_vpc.id
 
   tags = merge(
@@ -21,26 +25,29 @@ resource "aws_route_table" "default" {
 }
 
 resource "aws_main_route_table_association" "main_vpc_routes" {
+  count = var.vpc == null ? 1 : 0
+
   vpc_id         = data.aws_vpc.cluster_vpc.id
-  route_table_id = aws_route_table.default.id
+  route_table_id = aws_route_table.default[0].id
 }
 
 resource "aws_route" "igw_route" {
+  count = var.vpc == null ? 1 : 0
+
   destination_cidr_block = "0.0.0.0/0"
-  route_table_id         = aws_route_table.default.id
-  gateway_id             = aws_internet_gateway.igw.id
+  route_table_id         = aws_route_table.default[0].id
+  gateway_id             = aws_internet_gateway.igw[0].id
 
   timeouts {
     create = "20m"
   }
 }
 
 resource "aws_subnet" "public_subnet" {
-  count  = length(var.availability_zones)
-  vpc_id = data.aws_vpc.cluster_vpc.id
-
-  cidr_block = cidrsubnet(local.new_public_cidr_range, 3, count.index)
+  count = var.public_subnets == null ? length(var.availability_zones) : 0
 
+  vpc_id            = data.aws_vpc.cluster_vpc.id
+  cidr_block        = cidrsubnet(local.new_public_cidr_range, 3, count.index)
   availability_zone = var.availability_zones[count.index]
 
   tags = merge(
@@ -52,13 +59,14 @@ resource "aws_subnet" "public_subnet" {
 }
 
 resource "aws_route_table_association" "route_net" {
-  count          = length(var.availability_zones)
-  route_table_id = aws_route_table.default.id
+  count = var.public_subnets == null ? length(var.availability_zones) : 0
+
+  route_table_id = aws_route_table.default[0].id
   subnet_id      = aws_subnet.public_subnet[count.index].id
 }
 
 resource "aws_eip" "nat_eip" {
-  count = length(var.availability_zones)
+  count = var.public_subnets == null ? length(var.availability_zones) : 0
   vpc   = true
 
   tags = merge(
@@ -75,7 +83,8 @@ resource "aws_eip" "nat_eip" {
 }
 
 resource "aws_nat_gateway" "nat_gw" {
-  count         = length(var.availability_zones)
+  count = var.public_subnets == null ? length(var.availability_zones) : 0
+
   allocation_id = aws_eip.nat_eip[count.index].id
   subnet_id     = aws_subnet.public_subnet[count.index].id
 
@@ -86,4 +95,3 @@ resource "aws_nat_gateway" "nat_gw" {
     var.tags,
   )
 }
-

data/data/aws/vpc/vpc.tf

@@ -4,6 +4,8 @@ locals {
 }
 
 resource "aws_vpc" "new_vpc" {
+  count = var.vpc == null ? 1 : 0
+
   cidr_block           = var.cidr_block
   enable_dns_hostnames = true
   enable_dns_support   = true
@@ -17,7 +19,9 @@ resource "aws_vpc" "new_vpc" {
 }
 
 resource "aws_vpc_endpoint" "s3" {
-  vpc_id       = aws_vpc.new_vpc.id
+  count = var.vpc == null ? 1 : 0
+
+  vpc_id       = data.aws_vpc.cluster_vpc.id
   service_name = "com.amazonaws.${var.region}.s3"
   route_table_ids = concat(
     aws_route_table.private_routes.*.id,
@@ -26,14 +30,17 @@ resource "aws_vpc_endpoint" "s3" {
 }
 
 resource "aws_vpc_dhcp_options" "main" {
+  count = var.vpc == null ? 1 : 0
+
   domain_name         = var.region == "us-east-1" ? "ec2.internal" : format("%s.compute.internal", var.region)
   domain_name_servers = ["AmazonProvidedDNS"]
 
   tags = var.tags
 }
 
 resource "aws_vpc_dhcp_options_association" "main" {
-  vpc_id          = aws_vpc.new_vpc.id
-  dhcp_options_id = aws_vpc_dhcp_options.main.id
-}
+  count = var.vpc == null ? 1 : 0
 
+  vpc_id          = data.aws_vpc.cluster_vpc.id
+  dhcp_options_id = aws_vpc_dhcp_options.main[0].id
+}