Added fix for issue when no private subnets are defined (terraform-aws-modules#47)

* Added fix for issue when no private subnets are defined

* Minor readme

Author: antonbabenko

README.md

@@ -91,6 +91,7 @@ Examples
 
 * [Simple VPC](https://github.com/terraform-aws-modules/terraform-aws-vpc/tree/master/examples/simple-vpc)
 * [Complete VPC](https://github.com/terraform-aws-modules/terraform-aws-vpc/tree/master/examples/complete-vpc)
+* Few tests and edge cases examples: [#46](https://github.com/terraform-aws-modules/terraform-aws-vpc/tree/master/examples/issue-46-no-private-subnets), [#44](https://github.com/terraform-aws-modules/terraform-aws-vpc/tree/master/examples/issue-44-asymmetric-private-subnets)
 
 Authors
 -------

examples/complete-vpc/main.tf

@@ -29,28 +29,3 @@ module "vpc" {
     Name        = "complete"
   }
 }
-
-# This example creates resources which are not present in all AZs.
-# This should be seldomly needed from architectural point of view,
-# and it can also lead this module to some edge cases.
-module "not_symmetrical_vpc" {
-  source = "../../"
-
-  name = "not-symmetrical-example"
-
-  cidr = "10.0.0.0/16"
-
-  azs              = ["eu-west-1a", "eu-west-1b", "eu-west-1c"]
-  private_subnets  = ["10.0.1.0/24"]
-  public_subnets   = ["10.0.101.0/24", "10.0.102.0/24"]
-  database_subnets = ["10.0.21.0/24", "10.0.22.0/24", "10.0.23.0/24"]
-
-  create_database_subnet_group = true
-  enable_nat_gateway           = true
-
-  tags = {
-    Terraform   = "true"
-    Environment = "dev"
-    Name        = "not-symmetrical"
-  }
-}

examples/issue-44-asymmetric-private-subnets/README.md

@@ -0,0 +1,19 @@
+Issue 44 - VPC
+==============
+
+Configuration in this directory creates set of VPC resources to cover issues reported on GitHub:
+
+* https://github.com/terraform-aws-modules/terraform-aws-vpc/issues/44
+
+Usage
+=====
+
+To run this example you need to execute:
+
+```bash
+$ terraform init
+$ terraform plan
+$ terraform apply
+```
+
+Note that this example may create resources which can cost money (AWS Elastic IP, for example). Run `terraform destroy` when you don't need these resources.

examples/issue-44-asymmetric-private-subnets/main.tf

@@ -0,0 +1,27 @@
+# List of AZs and private subnets are not of equal length
+#
+# This example creates resources which are not present in all AZs.
+# This should be seldomly needed from architectural point of view,
+# and it can also lead this module to some edge cases.
+#
+# Github issue: https://github.com/terraform-aws-modules/terraform-aws-vpc/issues/44
+module "vpc" {
+  source = "../../"
+
+  name = "asymmetrical"
+
+  cidr = "10.0.0.0/16"
+
+  azs              = ["eu-west-1a", "eu-west-1b", "eu-west-1c"]
+  private_subnets  = ["10.0.1.0/24"]
+  public_subnets   = ["10.0.101.0/24", "10.0.102.0/24"]
+  database_subnets = ["10.0.21.0/24", "10.0.22.0/24", "10.0.23.0/24"]
+
+  create_database_subnet_group = true
+  enable_nat_gateway           = true
+
+  tags = {
+    Issue = "44"
+    Name  = "asymmetrical"
+  }
+}

examples/issue-44-asymmetric-private-subnets/outputs.tf

@@ -0,0 +1,32 @@
+# VPC
+output "vpc_id" {
+  description = "The ID of the VPC"
+  value       = "${module.vpc.vpc_id}"
+}
+
+# Subnets
+output "private_subnets" {
+  description = "List of IDs of private subnets"
+  value       = ["${module.vpc.private_subnets}"]
+}
+
+output "public_subnets" {
+  description = "List of IDs of public subnets"
+  value       = ["${module.vpc.public_subnets}"]
+}
+
+output "database_subnets" {
+  description = "List of IDs of database subnets"
+  value       = ["${module.vpc.database_subnets}"]
+}
+
+output "elasticache_subnets" {
+  description = "List of IDs of elasticache subnets"
+  value       = ["${module.vpc.elasticache_subnets}"]
+}
+
+# NAT gateways
+output "nat_public_ips" {
+  description = "List of public Elastic IPs created for AWS NAT Gateway"
+  value       = ["${module.vpc.nat_public_ips}"]
+}

examples/issue-46-no-private-subnets/README.md

@@ -0,0 +1,19 @@
+Issue 46 - VPC
+==============
+
+Configuration in this directory creates set of VPC resources to cover issues reported on GitHub:
+
+* https://github.com/terraform-aws-modules/terraform-aws-vpc/issues/46
+
+Usage
+=====
+
+To run this example you need to execute:
+
+```bash
+$ terraform init
+$ terraform plan
+$ terraform apply
+```
+
+Note that this example may create resources which can cost money (AWS Elastic IP, for example). Run `terraform destroy` when you don't need these resources.

examples/issue-46-no-private-subnets/main.tf

@@ -0,0 +1,25 @@
+# There are no private subnets in this VPC setup.
+#
+# Github issue: https://github.com/terraform-aws-modules/terraform-aws-vpc/issues/46
+module "vpc" {
+  source = "../../"
+
+  name = "no-private-subnets"
+
+  cidr = "10.0.0.0/16"
+
+  azs                 = ["eu-west-1a", "eu-west-1b", "eu-west-1c"]
+  public_subnets      = ["10.0.0.0/22", "10.0.4.0/22", "10.0.8.0/22"]
+  private_subnets     = []
+  database_subnets    = ["10.0.128.0/24", "10.0.129.0/24"]
+  elasticache_subnets = ["10.0.131.0/24", "10.0.132.0/24", "10.0.133.0/24"]
+
+  enable_dns_support   = true
+  enable_dns_hostnames = true
+  enable_nat_gateway   = false
+
+  tags = {
+    Issue = "46"
+    Name  = "no-private-subnets"
+  }
+}

examples/issue-46-no-private-subnets/outputs.tf

@@ -0,0 +1,32 @@
+# VPC
+output "vpc_id" {
+  description = "The ID of the VPC"
+  value       = "${module.vpc.vpc_id}"
+}
+
+# Subnets
+output "private_subnets" {
+  description = "List of IDs of private subnets"
+  value       = ["${module.vpc.private_subnets}"]
+}
+
+output "public_subnets" {
+  description = "List of IDs of public subnets"
+  value       = ["${module.vpc.public_subnets}"]
+}
+
+output "database_subnets" {
+  description = "List of IDs of database subnets"
+  value       = ["${module.vpc.database_subnets}"]
+}
+
+output "elasticache_subnets" {
+  description = "List of IDs of elasticache subnets"
+  value       = ["${module.vpc.elasticache_subnets}"]
+}
+
+# NAT gateways
+output "nat_public_ips" {
+  description = "List of public Elastic IPs created for AWS NAT Gateway"
+  value       = ["${module.vpc.nat_public_ips}"]
+}

main.tf

@@ -72,9 +72,10 @@ resource "aws_route" "public_internet_gateway" {
 
 #################
 # Private routes
+# There are so many route-tables as the largest amount of subnets of each type (really?)
 #################
 resource "aws_route_table" "private" {
-  count = "${length(var.private_subnets)}"
+  count = "${max(length(var.private_subnets), length(var.elasticache_subnets), length(var.database_subnets))}"
 
   vpc_id           = "${aws_vpc.this.id}"
   propagating_vgws = ["${var.private_propagating_vgws}"]