Add autoscaling policy and create ami_data module

modules/ami_data/main.tf

@@ -0,0 +1,20 @@
+data "aws_ami" "amazon_linux" {
+  most_recent = true
+
+  filter {
+    name   = "name"
+    values = ["amzn2-ami-*-gp2"]
+  }
+
+  filter {
+    name   = "architecture"
+    values = ["x86_64"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  owners = ["amazon"]
+}

modules/ami_data/outputs.tf

@@ -0,0 +1,3 @@
+output "amazon_linux" {
+  value = data.aws_ami.amazon_linux
+}

modules/app/main.tf

@@ -50,7 +50,7 @@ data "template_file" "bootstrap" {
 resource "aws_launch_configuration" "this" {
   name = "demo-app-launch-configuration"
 
-  image_id      = var.EC2_IMAGE_ID
+  image_id      = var.EC2_AMI
   instance_type = var.EC2_TYPE
 
   key_name        = var.EC2_KEY_NAME
@@ -80,10 +80,62 @@ resource "aws_autoscaling_group" "this" {
   }
 }
 
-resource "aws_autoscaling_policy" "this" {
-  name                   = "demo-app-autoscaling-policy"
-  scaling_adjustment     = 1
-  adjustment_type        = "ChangeInCapacity"
-  cooldown               = 300
+# asg scale up policy
+resource "aws_autoscaling_policy" "cpu-policy" {
+  name = "demo-app-cpu-policy"
+
   autoscaling_group_name = aws_autoscaling_group.this.name
+  adjustment_type        = "ChangeInCapacity"
+  scaling_adjustment     = "1"
+  cooldown               = "300"
+  policy_type            = "SimpleScaling"
+}
+
+resource "aws_cloudwatch_metric_alarm" "cpu-alarm" {
+  alarm_name          = "cpu-alarm"
+  alarm_description   = "cpu-alarm"
+  comparison_operator = "GreaterThanOrEqualToThreshold"
+  evaluation_periods  = "2"
+  metric_name         = "CPUUtilization"
+  namespace           = "AWS/EC2"
+  period              = "120"
+  statistic           = "Average"
+  threshold           = "30"
+
+  dimensions = {
+    "AutoScalingGroupName" = "${aws_autoscaling_group.this.name}"
+  }
+
+  actions_enabled = true
+  alarm_actions   = ["${aws_autoscaling_policy.cpu-policy.arn}"]
+}
+
+# asg scale down policy
+resource "aws_autoscaling_policy" "cpu-policy-scaledown" {
+  name = "demo-app-cpu-policy-scaledown"
+
+  autoscaling_group_name = aws_autoscaling_group.this.name
+  adjustment_type        = "ChangeInCapacity"
+  scaling_adjustment     = "-1"
+  cooldown               = "300"
+  policy_type            = "SimpleScaling"
+}
+
+resource "aws_cloudwatch_metric_alarm" "cpu-alarm-scaledown" {
+  alarm_name          = "cpu-alarm-scaledown"
+  alarm_description   = "cpu-alarm-scaledown"
+  comparison_operator = "LessThanOrEqualToThreshold"
+  evaluation_periods  = "2"
+  metric_name         = "CPUUtilization"
+  namespace           = "AWS/EC2"
+  period              = "120"
+  statistic           = "Average"
+  threshold           = "5"
+
+  dimensions = {
+    "AutoScalingGroupName" = "${aws_autoscaling_group.this.name}"
+  }
+
+  actions_enabled = true
+  alarm_actions   = ["${aws_autoscaling_policy.cpu-policy-scaledown.arn}"]
 }

modules/app/variables.tf

@@ -8,7 +8,7 @@ variable "VPC_SUBNETS_IDS" {
 }
 
 # EC2
-variable "EC2_IMAGE_ID" {
+variable "EC2_AMI" {
   type = string
 }
 

modules/bastion_host/main.tf

@@ -1,24 +1,3 @@
-data "aws_ami" "amazon-linux" {
-  most_recent = true
-
-  filter {
-    name   = "name"
-    values = ["amzn2-ami-*-gp2"]
-  }
-
-  filter {
-    name   = "architecture"
-    values = ["x86_64"]
-  }
-
-  filter {
-    name   = "virtualization-type"
-    values = ["hvm"]
-  }
-
-  owners = ["amazon"]
-}
-
 resource "aws_security_group" "this" {
   name = "bastion-host-sg"
 
@@ -50,9 +29,9 @@ resource "aws_network_interface" "this" {
 }
 
 resource "aws_instance" "this" {
-  ami           = data.aws_ami.amazon-linux.id
-  instance_type = var.INSTANCE_TYPE
-  key_name = var.KEY_NAME
+  ami           = var.EC2_AMI
+  instance_type = var.EC2_TYPE
+  key_name = var.EC2_KEY_NAME
 
   network_interface {
     network_interface_id = aws_network_interface.this.id
@@ -60,6 +39,6 @@ resource "aws_instance" "this" {
   }
 
   tags = {
-    Name = var.INSTANCE_NAME
+    Name = var.EC2_INSTANCE_NAME
   }
 }

modules/bastion_host/variables.tf

@@ -6,15 +6,19 @@ variable "SUBNET_ID" {
   type = string
 }
 
-variable "INSTANCE_TYPE" {
+variable "EC2_AMI" {
+  type = string
+}
+
+variable "EC2_TYPE" {
   type = string
   default = "t2.micro"
 }
 
-variable "INSTANCE_NAME" {
+variable "EC2_INSTANCE_NAME" {
   type = string
 }
 
-variable "KEY_NAME" {
+variable "EC2_KEY_NAME" {
   type = string
 }

prod/main.tf

@@ -27,13 +27,18 @@ module "vpc" {
 
 # Get VPC data
 module "vpc_data" {
-  depends_on = [module.vpc]
   source     = "../modules/vpc_data"
+  depends_on = [module.vpc]
 
   VPC_NAME        = var.DEMO_VPC_NAME
   BASTION_HOST_AZ = var.DEMO_BASTION_HOST_AZ
 }
 
+# Get AMI data
+module "ami_data" {
+  source = "../modules/ami_data"
+}
+
 # Create bastion host
 module "bastion_host" {
   source = "../modules/bastion_host"
@@ -41,30 +46,10 @@ module "bastion_host" {
   VPC_ID    = module.vpc_data.vpc.id
   SUBNET_ID = module.vpc_data.bastion_host_subnet.id
 
-  INSTANCE_TYPE = var.DEMO_BASTION_HOST_TYPE
-  INSTANCE_NAME = var.DEMO_BASTION_HOST_NAME
-  KEY_NAME      = var.DEMO_BASTION_HOST_KEY_NAME
-}
-
-data "aws_ami" "amazon-linux" {
-  most_recent = true
-
-  filter {
-    name   = "name"
-    values = ["amzn2-ami-*-gp2"]
-  }
-
-  filter {
-    name   = "architecture"
-    values = ["x86_64"]
-  }
-
-  filter {
-    name   = "virtualization-type"
-    values = ["hvm"]
-  }
-
-  owners = ["amazon"]
+  EC2_AMI           = module.ami_data.amazon_linux.id
+  EC2_TYPE          = var.DEMO_BASTION_HOST_TYPE
+  EC2_INSTANCE_NAME = var.DEMO_BASTION_HOST_NAME
+  EC2_KEY_NAME      = var.DEMO_BASTION_HOST_KEY_NAME
 }
 
 # Create demo app
@@ -74,7 +59,7 @@ module "app" {
   VPC_ID          = module.vpc_data.vpc.id
   VPC_SUBNETS_IDS = module.vpc_data.private_subnets.ids
 
-  EC2_IMAGE_ID = data.aws_ami.amazon-linux.id
+  EC2_AMI      = module.ami_data.amazon_linux.id
   EC2_TYPE     = var.DEMO_APP_EC2_TYPE
   EC2_KEY_NAME = var.DEMO_APP_EC2_KEY_NAME