New: module autoscaling-policy-metric-alarm-pair

Abstract usage of autoscaling policy and cloudwatch alarm to autoscale
ASG.

By moving the code from load-asg example. Example load-asg is using the
new module now.

Author: Magicloud

CHANGELOG.md

@@ -1,5 +1,9 @@
 # (Unreleased)
 
+### Modules
+
+* `autoscaling-policy-metric-alarm-pair`: New module abstracts the autoscaling function from example load-asg. The example now is using this module.
+
 # v0.9.0
 
 ### Summary

examples/load-asg/main.tf

@@ -122,8 +122,8 @@ module "web-asg" {
   name_prefix   = "${var.name}-${var.web_app_name}"
   elb_names     = [aws_elb.web.name]
   instance_type = var.instance_type
-  max_nodes     = "10"
-  min_nodes     = "2"
+  max_nodes     = 10
+  min_nodes     = 2
   public_ip     = false
   key_name      = aws_key_pair.main.key_name
   subnet_ids    = module.vpc.public_subnet_ids
@@ -167,108 +167,17 @@ END_INIT
 
 }
 
-## Autoscaling Policies
-
-# ASG Policy Up
-
-resource "aws_autoscaling_policy" "cpu_up" {
-  name                   = "${var.name}-asg-policy-cpu-up"
-  autoscaling_group_name = module.web-asg.name
-  adjustment_type        = "ChangeInCapacity"
-  cooldown               = 300
-  scaling_adjustment     = 3
-  policy_type            = "SimpleScaling"
-}
-
-resource "aws_autoscaling_policy" "mem_up" {
-  name                   = "${var.name}-asg-policy-mem-up"
-  autoscaling_group_name = module.web-asg.name
-  adjustment_type        = "ChangeInCapacity"
-  cooldown               = 300
-  scaling_adjustment     = 3
-  policy_type            = "SimpleScaling"
-}
-
-# Cloudwatch Monitor CPU Up
-resource "aws_cloudwatch_metric_alarm" "web_cpu_scale_up" {
-  alarm_name          = "${var.name}-cpu-scale-up-alarm"
-  comparison_operator = "GreaterThanOrEqualToThreshold"
-  evaluation_periods  = "3"
-  metric_name         = "CPUUtilization"
-  namespace           = "AWS/EC2"
-  period              = "60"
-  statistic           = "Average"
-  threshold           = "60"
-  dimensions = {
-    AutoScalingGroupName = module.web-asg.name
-  }
-  alarm_actions = [aws_autoscaling_policy.cpu_up.arn]
-}
-
-# Cloudwatch Monitor Memory Up
-resource "aws_cloudwatch_metric_alarm" "web_mem_scale_up" {
-  alarm_name          = "${var.name}-mem-scale-up-alarm"
-  comparison_operator = "GreaterThanOrEqualToThreshold"
-  evaluation_periods  = "3"
-  metric_name         = "MemoryUtilization"
-  namespace           = "AWS/EC2"
-  period              = "60"
-  statistic           = "Average"
-  threshold           = "60"
-  dimensions = {
-    AutoScalingGroupName = module.web-asg.name
-  }
-  alarm_actions = [aws_autoscaling_policy.mem_up.arn]
-}
-
-# ASG Policy Down
-resource "aws_autoscaling_policy" "cpu_down" {
-  name                   = "${var.name}-asg-policy-cpu-down"
-  autoscaling_group_name = module.web-asg.name
-  adjustment_type        = "ChangeInCapacity"
-  cooldown               = 300
-  scaling_adjustment     = -2
-  policy_type            = "SimpleScaling"
-}
-
-resource "aws_autoscaling_policy" "mem_down" {
-  name                   = "${var.name}-asg-policy-mem-down"
-  autoscaling_group_name = module.web-asg.name
-  adjustment_type        = "ChangeInCapacity"
-  cooldown               = 300
-  scaling_adjustment     = -2
-  policy_type            = "SimpleScaling"
+module "web_cpu_autoscaling" {
+  source = "../../modules/autoscaling-policy-metric-alarm-pair"
+  name = var.name
+  asg_name = module.web-asg.name
+  metric = "CPUUtilization"
 }
 
-# Cloudwatch CPU Monitor Down
-resource "aws_cloudwatch_metric_alarm" "web_cpu_scale_down" {
-  alarm_name          = "${var.name}-cpu-scale-down-alarm"
-  comparison_operator = "LessThanOrEqualToThreshold"
-  evaluation_periods  = "3"
-  metric_name         = "CPUUtilization"
-  namespace           = "AWS/EC2"
-  period              = "60"
-  statistic           = "Average"
-  threshold           = "30"
-  dimensions = {
-    AutoScalingGroupName = module.web-asg.name
-  }
-  alarm_actions = [aws_autoscaling_policy.cpu_down.arn]
-}
-
-# Cloudwatch Memory Monitor Down
-resource "aws_cloudwatch_metric_alarm" "web_mem_scale_down" {
-  alarm_name          = "${var.name}-mem-scale-down-alarm"
-  comparison_operator = "LessThanOrEqualToThreshold"
-  evaluation_periods  = "3"
-  metric_name         = "MemoryUtilization"
-  namespace           = "AWS/EC2"
-  period              = "60"
-  statistic           = "Average"
-  threshold           = "30"
-  dimensions = {
-    AutoScalingGroupName = module.web-asg.name
-  }
-  alarm_actions = [aws_autoscaling_policy.mem_down.arn]
+module "web_mem_autoscaling" {
+  source = "../../modules/autoscaling-policy-metric-alarm-pair"
+  name = var.name
+  asg_name = module.web-asg.name
+  metric = "MemoryUtilization"
 }
 

modules/autoscaling-policy-metric-alarm-pair/main.tf

@@ -0,0 +1,123 @@
+variable "name" {
+  description = "Prefix of the AutoScaling Policy."
+  type = string
+}
+
+variable "asg_name" {
+  description = "Name of the AutoScaling Group that this policy would apply to."
+  type = string
+}
+
+variable "metric" {
+  description = "CPUUtilization or MemoryUtilization"
+  type = string
+}
+
+variable "up_evaluation_periods" {
+  default     = 3
+  description = ""
+  type = number
+}
+
+variable "up_period" {
+  default     = 60
+  description = ""
+  type = number
+}
+
+variable "up_threshold" {
+  default     = 60
+  description = ""
+  type = number
+}
+
+variable "up_scaling_adjustment" {
+  default     = 3
+  description = ""
+  type = number
+}
+
+variable "up_cooldown" {
+  default     = 300
+  description = ""
+  type = number
+}
+
+variable "down_evaluation_periods" {
+  default     = 3
+  description = ""
+  type = number
+}
+
+variable "down_period" {
+  default     = 60
+  description = ""
+  type = number
+}
+
+variable "down_threshold" {
+  default     = 30
+  description = ""
+  type = number
+}
+
+variable "down_scaling_adjustment" {
+  default     = 2
+  description = ""
+  type = number
+}
+
+variable "down_cooldown" {
+  default     = 300
+  description = ""
+  type = number
+}
+
+resource "aws_autoscaling_policy" "scale_up" {
+  name                   = "${var.name}-asp-up"
+  autoscaling_group_name = var.asg_name
+  adjustment_type        = "ChangeInCapacity"
+  cooldown               = var.up_cooldown
+  scaling_adjustment     = var.up_scaling_adjustment
+  policy_type            = "SimpleScaling"
+}
+
+resource "aws_cloudwatch_metric_alarm" "scale_up" {
+  alarm_name          = "${var.name}-scale-up-alarm"
+  comparison_operator = "GreaterThanOrEqualToThreshold"
+  evaluation_periods  = var.up_evaluation_periods
+  metric_name         = var.metric
+  namespace           = "AWS/EC2"
+  period              = var.up_period
+  statistic           = "Average"
+  threshold           = var.up_threshold
+  dimensions = {
+    AutoScalingGroupName = var.asg_name
+  }
+  alarm_actions = [aws_autoscaling_policy.scale_up.arn]
+}
+
+resource "aws_autoscaling_policy" "scale_down" {
+  name                   = "${var.name}-asp-down"
+  autoscaling_group_name = var.asg_name
+  adjustment_type        = "ChangeInCapacity"
+  cooldown               = var.down_cooldown
+  scaling_adjustment     = "-${var.down_scaling_adjustment}"
+  policy_type            = "SimpleScaling"
+}
+
+resource "aws_cloudwatch_metric_alarm" "scale_down" {
+  alarm_name          = "${var.name}-scale-down-alarm"
+  comparison_operator = "LessThanOrEqualToThreshold"
+  evaluation_periods  = var.down_evaluation_periods
+  metric_name         = var.metric
+  namespace           = "AWS/EC2"
+  period              = var.down_period
+  statistic           = "Average"
+  threshold           = var.down_threshold
+  dimensions = {
+    AutoScalingGroupName = var.asg_name
+  }
+  alarm_actions = [aws_autoscaling_policy.scale_down.arn]
+}
+

modules/autoscaling-policy-metric-alarm-pair/versions.tf

@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}