New function: single-node-asg module supports binding EIP by itself.

Since it is single node, binding an EIP to the instance is possible. And
it eases other things since the public interface is constant.

Add assign_eip variable to single-node-asg. If turns it on, an EIP will
be allocated, and assocated with the instance.

Scope VPC is specified in case the account does not have a default VPC.

modules/single-node-asg/main.tf

@@ -52,6 +52,32 @@ module "service-data" {
   iam_instance_profile_role_name = module.instance_profile.iam_role_name
 }
 
+resource "aws_eip" "eip" {
+  count = var.assign_eip ? 1 : 0
+  vpc   = true
+}
+
+resource "aws_iam_role_policy_attachment" "associate_eip" {
+  role       = module.instance_profile.iam_role_name
+  policy_arn = aws_iam_policy.associate_eip_policy.arn
+}
+
+resource "aws_iam_policy" "associate_eip_policy" {
+  name   = "associate_address"
+  policy = data.aws_iam_policy_document.associate_eip_policy_doc.json
+}
+
+data "aws_iam_policy_document" "associate_eip_policy_doc" {
+  statement {
+    sid    = ""
+    effect = "Allow"
+    actions = [
+      "ec2:AssociateAddress"
+    ]
+    resources = ["*"]
+  }
+}
+
 # Create an ASG with just 1 EC2 instance
 module "server" {
   source = "../asg"
@@ -66,12 +92,11 @@ module "server" {
   max_nodes       = 1
   min_nodes       = 1
   placement_group = var.placement_group
-  public_ip       = var.public_ip
+  public_ip       = var.assign_eip ? false : var.public_ip
   # the prefix and suffix names are combined in
   # the `asg` module to create the full name
-  name_prefix = var.name_prefix
-  name_suffix = "${var.name_suffix}-${local.az}"
-
+  name_prefix        = var.name_prefix
+  name_suffix        = "${var.name_suffix}-${local.az}"
   root_volume_type   = var.root_volume_type
   root_volume_size   = var.root_volume_size
   security_group_ids = var.security_group_ids
@@ -84,7 +109,12 @@ module "server" {
 # exec > /tmp/init.log
 # exec 2> /tmp/init-err.log
 # set -x
+apt update
 ${var.init_prefix}
+${module.init-install-awscli.init_snippet}
+while ! ${var.assign_eip ? "aws ec2 associate-address --instance-id \"$(ec2metadata --instance-id)\" --region \"${var.region}\" --allocation-id \"${element(aws_eip.eip.*.id, 0)}\"" : "true"}; do
+  sleep 1
+done
 ${module.init-attach-ebs.init_snippet}
 ${var.init_suffix}
 END_INIT
@@ -97,3 +127,7 @@ module "init-attach-ebs" {
   region    = var.region
   volume_id = module.service-data.volume_id
 }
+
+module "init-install-awscli" {
+  source = "../init-snippet-install-awscli"
+}

modules/single-node-asg/outputs.tf

@@ -12,3 +12,7 @@ output "data_volume_name_tag" {
   value       = "${local.data_volume_name_prefix}-${local.az}"
   description = "Name tag value for attached data volume"
 }
+
+output "eip_address" {
+  value = var.assign_eip ? aws_eip.eip.*[0].public_ip : ""
+}

modules/single-node-asg/variables.tf

@@ -62,7 +62,7 @@ variable "data_volume_size" {
 variable "data_volume_encrypted" {
   default     = true
   description = "Boolean, whether or not to encrypt the EBS block device"
-  type        = string
+  type        = bool
 }
 
 variable "data_volume_kms_key_id" {
@@ -98,7 +98,7 @@ variable "init_suffix" {
 variable "public_ip" {
   default     = true
   description = "Boolean flag to enable/disable `map_public_ip_on_launch` in the launch configuration"
-  type        = string
+  type        = bool
 }
 
 variable "subnet_id" {
@@ -121,3 +121,9 @@ variable "load_balancers" {
   description = "The list of load balancers names to pass to the ASG module"
   type        = list(string)
 }
+
+variable "assign_eip" {
+  default     = false
+  description = "Whether or not associating an EIP with the node."
+  type        = bool
+}