make subnet cidr block assignment reproducible

Author: dfry

main.tf

@@ -1,6 +1,6 @@
 locals {
-  all_pub_subnets  = merge({"management" = data.aws_availability_zones.available.names[0]}, {for pair in setproduct(var.environments, data.aws_availability_zones.available.names) : "${pair[0]}-${pair[1]}" => pair[1]})
-  all_priv_subnets = {for pair in setproduct(var.environments, data.aws_availability_zones.available.names) : "${pair[0]}-${pair[1]}" => pair[1]}
+  all_pub_subnets  = merge({"management" = {env = "management", az = data.aws_availability_zones.available.names[0], cidr_block_index = 0}}, {for pair in setproduct(var.environments, data.aws_availability_zones.available.names) : "${pair[0]}-${pair[1]}" => {env = pair[0], az  = pair[1], cidr_block_index = 1 + index(data.aws_availability_zones.available.names, pair[1]) + (var.cidr_block_index[pair[0]]) * length(data.aws_availability_zones.available.names)}})
+  all_priv_subnets = {for pair in setproduct(var.environments, data.aws_availability_zones.available.names) : "${pair[0]}-${pair[1]}" => {env = pair[0], az  = pair[1], cidr_block_index = index(data.aws_availability_zones.available.names, pair[1]) + (var.cidr_block_index[pair[0]]) * length(data.aws_availability_zones.available.names)}}
 }
 
 module "ubuntu-bionic-ami" {

modules/named-subnets/private.tf

@@ -15,8 +15,8 @@ module "private_label" {
 resource "aws_subnet" "private" {
   for_each          = local.private_subnet_az_map
   vpc_id            = var.vpc_id
-  availability_zone = each.value
-  cidr_block        = cidrsubnet(var.cidr_block, ceil(log(var.max_subnets, 2)), index(keys(local.private_subnet_az_map), each.key))
+  availability_zone = each.value.az
+  cidr_block        = cidrsubnet(var.cidr_block, ceil(log(var.max_subnets, 2)), each.value.cidr_block_index)
 
   tags = {
     "Name"      = "${module.private_label.id}${var.delimiter}${each.key}"

modules/named-subnets/public.tf

@@ -17,8 +17,8 @@ module "public_label" {
 resource "aws_subnet" "public" {
   for_each          = local.public_subnet_az_map
   vpc_id            = var.vpc_id
-  availability_zone = each.value
-  cidr_block        = cidrsubnet(var.cidr_block, ceil(log(var.max_subnets, 2)), index(keys(local.public_subnet_az_map), each.key))
+  availability_zone = each.value.az
+  cidr_block        = cidrsubnet(var.cidr_block, ceil(log(var.max_subnets, 2)), each.value.cidr_block_index)
 
   tags = {
     "Name"      = "${module.public_label.id}${var.delimiter}${each.key}"

variables.tf

@@ -70,6 +70,14 @@ variable "environments" {
   default     = ["dev"]
 }
 
+variable "cidr_block_index" {
+  description = "map of environments for the tenatn. Each environment will contain an instance of Mojaloop and associated services."
+  type        = map(number)
+  default     = {
+      "dev" = 0
+  }
+}
+
 variable "public_subnets" {
   default     = ["gateway", "management", "simulators"]
   type        = list(string)