Auto Scaling Configuration

Introduction

Steps to create auto scaling (A.S), two main concepts

1. Configuration
   • What to scale out
   • Instance settings related
2. Scaling groups
   • Where to scale out：VPC, subnet, LB etc
   • How many and what condition to scale：Scaling policies

Create A.S Configuration

1. Select AMI
2. Select instance type
3. Configure details
   
   
4. Select storage
5. Select security group (S.G)
6. Select pem
7. Completed view
   

Create A.S Group

1. Select the source configuration for A.S group
   
   
2. Configure details
   
   
3. Configure scaling policies, which can be set here or later
   
   
4. Configure notification here or later
   
   
5. Configure tags which will auto tag instance when scaling out
   

Result

Right after setting up, A.S is creating an new instance due to the difference between desired and current instance quantity. Click Edit to modify any setting accordingly

Clink Instance tag to view instances and its condition under this A.S

Confirm the instance status by checking the EC2 service main section

Check A.S Activity History to understand what A.S has done

Configure Scaling Policy

Click Add policy under Scaling Policies tag, click Create simple scaling policy

Give a name and set take the action, which is to add an instance.
Condition, Execute policy when, can be set here but we will set it later elsewhere.

Repeat the step to create an action to decrease an instance.

Completed view of Scaling policies. Notice that the Execute policy when has not been set yet, which we will do it elsewhere later.

Create Alarm under CloudWatch (C.W)

Create alarms under C.W to monitor certain condition of instances and trigger action created on steps above when condition is met

In this example we will monitor the metrics in A.S group

Select the metric to monitor, in this case, CPUUtilization is selected

Set the condition to be triggered
Whenever section is the place to set the condition
Actions section is the place to set what to do when condition is met. In this case, we want to scale out when condition is met, so delete the default action which is SNS notification and click on AutoScaling Action
Period is the time range to be monitor

Completed view. This configuration is saying

1. In every 1 minute monitored data point
2. If any monitored data point, wich is CPUUtilization, is more than 50%
3. Execute Actions, which is the scale policy action created in A.S group
   

Repeat the step to create a monitor policy to decrease instance when CPUUtilization is lower then 30%

Completed view of two alarms
CPUUtilization is lower then 30% so lowCPU is in alarm state

Go back to Scaling Policies under A.S, the Execute policy when section has the condition information now which is the settings did in C.W

A.S Testing

1. Increase instance CPU loading
   
   
   
2. A.S responds to high CPU loading
   
   
3. Checking C.W. highCPU alarm is triggered so it executes the scaling policy set in A.S group
   
   
4. Checking scaling policy in A.S.