AwsHow-ToBeginner · 4 min read

How to Configure Auto Scaling in AWS: Step-by-Step Guide

To configure auto scaling in AWS, create an Auto Scaling Group linked to a Launch Template or Launch Configuration that defines your EC2 instances. Set scaling policies based on metrics like CPU usage to automatically add or remove instances as demand changes.

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Syntax

An AWS Auto Scaling setup mainly involves these parts:

Launch Template/Configuration: Defines the EC2 instance settings like AMI, instance type, and security groups.
Auto Scaling Group (ASG): Manages a group of EC2 instances using the launch template and controls scaling.
Scaling Policies: Rules that tell AWS when to add or remove instances based on metrics.

bash

aws ec2 create-launch-template --launch-template-name MyTemplate --version-description v1 --launch-template-data '{"ImageId":"ami-0abcdef1234567890","InstanceType":"t3.micro"}'

aws autoscaling create-auto-scaling-group --auto-scaling-group-name MyASG --launch-template LaunchTemplateName=MyTemplate,Version=1 --min-size 1 --max-size 3 --desired-capacity 1 --vpc-zone-identifier subnet-12345678

aws autoscaling put-scaling-policy --auto-scaling-group-name MyASG --policy-name CpuScalingPolicy --policy-type TargetTrackingScaling --target-tracking-configuration '{"PredefinedMetricSpecification":{"PredefinedMetricType":"ASGAverageCPUUtilization"},"TargetValue":50.0}'

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Example

This example shows how to create a launch template, an auto scaling group, and a CPU-based scaling policy using AWS CLI commands.

bash

aws ec2 create-launch-template --launch-template-name ExampleTemplate --version-description v1 --launch-template-data '{"ImageId":"ami-0abcdef1234567890","InstanceType":"t3.micro"}'

aws autoscaling create-auto-scaling-group --auto-scaling-group-name ExampleASG --launch-template LaunchTemplateName=ExampleTemplate,Version=1 --min-size 1 --max-size 4 --desired-capacity 2 --vpc-zone-identifier subnet-12345678

aws autoscaling put-scaling-policy --auto-scaling-group-name ExampleASG --policy-name CpuScaleOut --policy-type TargetTrackingScaling --target-tracking-configuration '{"PredefinedMetricSpecification":{"PredefinedMetricType":"ASGAverageCPUUtilization"},"TargetValue":60.0}'

Output

Launch template created with ID: lt-0abcd1234efgh5678 Auto Scaling group created: ExampleASG Scaling policy created: CpuScaleOut

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Common Pitfalls

Not specifying the correct subnets in the Auto Scaling Group can cause instances to fail launching.
Using outdated launch configurations instead of launch templates can limit features and flexibility.
Setting scaling policies with too aggressive thresholds may cause frequent scaling actions, increasing costs.
Forgetting to attach proper IAM roles or security groups can block instance startup or communication.

bash

aws autoscaling create-auto-scaling-group --auto-scaling-group-name BadASG --launch-configuration-name OldConfig --min-size 1 --max-size 3 --desired-capacity 1

# Right way is to use launch templates:
aws autoscaling create-auto-scaling-group --auto-scaling-group-name GoodASG --launch-template LaunchTemplateName=MyTemplate,Version=1 --min-size 1 --max-size 3 --desired-capacity 1

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Quick Reference

Remember these key points when configuring AWS Auto Scaling:

Use Launch Templates for flexible instance configuration.
Define Auto Scaling Groups with proper subnet and size limits.
Set scaling policies based on metrics like CPU or network usage.
Test scaling behavior with load to ensure smooth operation.

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Key Takeaways

Create a launch template to define your EC2 instance settings.

Use an Auto Scaling Group to manage instance count and placement.

Set scaling policies to automatically adjust capacity based on demand.

Always specify correct subnets and security settings to avoid launch failures.

Test your auto scaling setup to ensure it responds correctly to load changes.