Creates a single private route table when single_nat_gateway is true (#83)

Fixes #82

main.tf

@@ -4,6 +4,7 @@ terraform {
 
 locals {
   max_subnet_length = "${max(length(var.private_subnets), length(var.elasticache_subnets), length(var.database_subnets), length(var.redshift_subnets))}"
+  nat_gateway_count = "${var.single_nat_gateway ? 1 : local.max_subnet_length}"
 }
 
 ######
@@ -80,11 +81,11 @@ resource "aws_route" "public_internet_gateway" {
 # There are so many routing tables as the largest amount of subnets of each type (really?)
 #################
 resource "aws_route_table" "private" {
-  count = "${var.create_vpc && local.max_subnet_length > 0 ? local.max_subnet_length : 0}"
+  count = "${var.create_vpc && local.max_subnet_length > 0 ? local.nat_gateway_count : 0}"
 
   vpc_id = "${aws_vpc.this.id}"
 
-  tags = "${merge(var.tags, var.private_route_table_tags, map("Name", format("%s-private-%s", var.name, element(var.azs, count.index))))}"
+  tags = "${merge(var.tags, var.private_route_table_tags, map("Name", (var.single_nat_gateway ? "${var.name}-private" : format("%s-private-%s", var.name, element(var.azs, count.index)))))}"
 
   lifecycle {
     # When attaching VPN gateways it is common to define aws_vpn_gateway_route_propagation
@@ -203,7 +204,7 @@ locals {
 }
 
 resource "aws_eip" "nat" {
-  count = "${var.create_vpc && (var.enable_nat_gateway && !var.reuse_nat_ips) ? (var.single_nat_gateway ? 1 : length(var.azs)) : 0}"
+  count = "${var.create_vpc && (var.enable_nat_gateway && !var.reuse_nat_ips) ? local.nat_gateway_count : 0}"
 
   vpc = true
 
@@ -211,7 +212,7 @@ resource "aws_eip" "nat" {
 }
 
 resource "aws_nat_gateway" "this" {
-  count = "${var.create_vpc && var.enable_nat_gateway ? (var.single_nat_gateway ? 1 : length(var.azs)) : 0}"
+  count = "${var.create_vpc && var.enable_nat_gateway ? local.nat_gateway_count : 0}"
 
   allocation_id = "${element(local.nat_gateway_ips, (var.single_nat_gateway ? 0 : count.index))}"
   subnet_id     = "${element(aws_subnet.public.*.id, (var.single_nat_gateway ? 0 : count.index))}"
@@ -222,7 +223,7 @@ resource "aws_nat_gateway" "this" {
 }
 
 resource "aws_route" "private_nat_gateway" {
-  count = "${var.create_vpc && var.enable_nat_gateway ? length(var.private_subnets) : 0}"
+  count = "${var.create_vpc && var.enable_nat_gateway ? local.nat_gateway_count : 0}"
 
   route_table_id         = "${element(aws_route_table.private.*.id, count.index)}"
   destination_cidr_block = "0.0.0.0/0"
@@ -246,7 +247,7 @@ resource "aws_vpc_endpoint" "s3" {
 }
 
 resource "aws_vpc_endpoint_route_table_association" "private_s3" {
-  count = "${var.create_vpc && var.enable_s3_endpoint ? length(var.private_subnets) : 0}"
+  count = "${var.create_vpc && var.enable_s3_endpoint ? local.nat_gateway_count : 0}"
 
   vpc_endpoint_id = "${aws_vpc_endpoint.s3.id}"
   route_table_id  = "${element(aws_route_table.private.*.id, count.index)}"
@@ -276,7 +277,7 @@ resource "aws_vpc_endpoint" "dynamodb" {
 }
 
 resource "aws_vpc_endpoint_route_table_association" "private_dynamodb" {
-  count = "${var.create_vpc && var.enable_dynamodb_endpoint ? length(var.private_subnets) : 0}"
+  count = "${var.create_vpc && var.enable_dynamodb_endpoint ? local.nat_gateway_count : 0}"
 
   vpc_endpoint_id = "${aws_vpc_endpoint.dynamodb.id}"
   route_table_id  = "${element(aws_route_table.private.*.id, count.index)}"
@@ -296,28 +297,28 @@ resource "aws_route_table_association" "private" {
   count = "${var.create_vpc && length(var.private_subnets) > 0 ? length(var.private_subnets) : 0}"
 
   subnet_id      = "${element(aws_subnet.private.*.id, count.index)}"
-  route_table_id = "${element(aws_route_table.private.*.id, count.index)}"
+  route_table_id = "${element(aws_route_table.private.*.id, (var.single_nat_gateway ? 0 : count.index))}"
 }
 
 resource "aws_route_table_association" "database" {
   count = "${var.create_vpc && length(var.database_subnets) > 0 ? length(var.database_subnets) : 0}"
 
   subnet_id      = "${element(aws_subnet.database.*.id, count.index)}"
-  route_table_id = "${element(aws_route_table.private.*.id, count.index)}"
+  route_table_id = "${element(aws_route_table.private.*.id, (var.single_nat_gateway ? 0 : count.index))}"
 }
 
 resource "aws_route_table_association" "redshift" {
   count = "${var.create_vpc && length(var.redshift_subnets) > 0 ? length(var.redshift_subnets) : 0}"
 
   subnet_id      = "${element(aws_subnet.redshift.*.id, count.index)}"
-  route_table_id = "${element(aws_route_table.private.*.id, count.index)}"
+  route_table_id = "${element(aws_route_table.private.*.id, (var.single_nat_gateway ? 0 : count.index))}"
 }
 
 resource "aws_route_table_association" "elasticache" {
   count = "${var.create_vpc && length(var.elasticache_subnets) > 0 ? length(var.elasticache_subnets) : 0}"
 
   subnet_id      = "${element(aws_subnet.elasticache.*.id, count.index)}"
-  route_table_id = "${element(aws_route_table.private.*.id, count.index)}"
+  route_table_id = "${element(aws_route_table.private.*.id, (var.single_nat_gateway ? 0 : count.index))}"
 }
 
 resource "aws_route_table_association" "public" {