AWS CloudFormation Auto Scaling

Overview

Create production-ready Auto Scaling infrastructure using AWS CloudFormation templates. This skill covers Auto Scaling Groups for EC2, ECS, and Lambda, launch configurations, launch templates, scaling policies, lifecycle hooks, and best practices for high availability and cost optimization.

When to Use

Use this skill when:

• Creating Auto Scaling Groups for EC2 instances
• Configuring Launch Configurations or Launch Templates
• Implementing scaling policies (step, target tracking, simple)
• Adding lifecycle hooks for lifecycle management
• Creating scaling for ECS services
• Implementing Lambda provisioned concurrency scaling
• Organizing templates with Parameters, Outputs, Mappings, Conditions
• Implementing cross-stack references with export/import
• Using mixed instances policies for diversity

Instructions

Follow these steps to create Auto Scaling infrastructure with CloudFormation:

1. Define Parameters

Specify capacity and instance settings with AWS-specific parameter types:

Parameters:
  MinSize:
    Type: Number
    Default: 2
    Description: Minimum number of instances

  MaxSize:
    Type: Number
    Default: 10
    Description: Maximum number of instances

  DesiredCapacity:
    Type: Number
    Default: 2
    Description: Desired number of instances

  InstanceType:
    Type: AWS::EC2::Instance::Type
    Default: t3.micro
    Description: EC2 instance type

  AmiId:
    Type: AWS::EC2::Image::Id
    Description: AMI ID for instances

  SubnetIds:
    Type: List<AWS::EC2::Subnet::Id>
    Description: Subnets for Auto Scaling group

2. Create Launch Configuration

Define instance launch settings:

Resources:
  MyLaunchConfiguration:
    Type: AWS::AutoScaling::LaunchConfiguration
    Properties:
      LaunchConfigurationName: !Sub "${AWS::StackName}-lc"
      ImageId: !Ref AmiId
      InstanceType: !Ref InstanceType
      KeyName: !Ref KeyName
      SecurityGroups:
        - !Ref InstanceSecurityGroup
      InstanceMonitoring: Enabled
      UserData:
        Fn::Base64: |
          #!/bin/bash
          yum update -y
          yum install -y httpd
          systemctl start httpd

3. Create Auto Scaling Group

Specify min/max/desired capacity and networking:

Resources:
  MyAutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      AutoScalingGroupName: !Sub "${AWS::StackName}-asg"
      MinSize: !Ref MinSize
      MaxSize: !Ref MaxSize
      DesiredCapacity: !Ref DesiredCapacity
      VPCZoneIdentifier: !Ref SubnetIds
      LaunchConfigurationName: !Ref MyLaunchConfiguration
      TargetGroupARNs:
        - !Ref MyTargetGroup
      HealthCheckType: ELB
      HealthCheckGracePeriod: 300
      Tags:
        - Key: Environment
          Value: !Ref Environment
          PropagateAtLaunch: true

4. Configure Load Balancer Integration

Set up ALB for traffic distribution:

Resources:
  MyTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      Name: !Sub "${AWS::StackName}-tg"
      Port: 80
      Protocol: HTTP
      VpcId: !Ref VPCId
      HealthCheckPath: /
      TargetType: instance

  MyLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Name: !Sub "${AWS::StackName}-alb"
      Scheme: internet-facing
      Type: application
      Subnets:
        - !Ref PublicSubnet1
        - !Ref PublicSubnet2

5. Add Scaling Policies

Implement target tracking scaling:

Resources:
  TargetTrackingPolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      PolicyName: !Sub "${AWS::StackName}-target-tracking"
      PolicyType: TargetTrackingScaling
      AutoScalingGroupName: !Ref MyAutoScalingGroup
      TargetTrackingConfiguration:
        PredefinedMetricSpecification:
          PredefinedMetricType: ASGAverageCPUUtilization
        TargetValue: 70
        DisableScaleIn: false

6. Configure Lifecycle Hooks

Implement hooks for graceful instance management:

Resources:
  LifecycleHookTermination:
    Type: AWS::AutoScaling::LifecycleHook
    Properties:
      LifecycleHookName: !Sub "${AWS::StackName}-termination-hook"
      AutoScalingGroupName: !Ref MyAutoScalingGroup
      LifecycleTransition: autoscaling:EC2_INSTANCE_TERMINATING
      HeartbeatTimeout: 300
      NotificationTargetARN: !Ref SNSTopic
      RoleARN: !Ref LifecycleHookRole

7. Set Up Monitoring

Configure CloudWatch alarms for scaling triggers:

Resources:
  HighCpuAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmName: !Sub "${AWS::StackName}-high-cpu"
      MetricName: CPUUtilization
      Namespace: AWS/EC2
      Dimensions:
        - Name: AutoScalingGroupName
          Value: !Ref MyAutoScalingGroup
      Statistic: Average
      Period: 60
      EvaluationPeriods: 3
      Threshold: 70
      ComparisonOperator: GreaterThanThreshold

8. Configure Outputs and Cross-Stack References

Export ASG configuration for other stacks:

Outputs:
  AutoScalingGroupName:
    Description: Name of the Auto Scaling Group
    Value: !Ref MyAutoScalingGroup
    Export:
      Name: !Sub "${AWS::StackName}-AutoScalingGroupName"

  AutoScalingGroupArn:
    Description: ARN of the Auto Scaling Group
    Value: !GetAtt MyAutoScalingGroup.AutoScalingGroupArn
    Export:
      Name: !Sub "${AWS::StackName}-AutoScalingGroupArn"

Examples

Complete Auto Scaling Template

Full end-to-end template with VPC, ASG, ALB, and scaling policies:

AWSTemplateFormatVersion: '2010-09-09'
Description: Auto Scaling Group with ALB integration

Parameters:
  Environment:
    Type: String
    Default: production
  InstanceType:
    Type: AWS::EC2::Instance::Type
    Default: t3.micro
  AmiId:
    Type: AWS::EC2::Image::Id
  VpcId:
    Type: AWS::EC2::VPC::Id
  SubnetIds:
    Type: List<AWS::EC2::Subnet::Id>

Resources:
  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Security group for ASG instances
      VpcId: !Ref VpcId
      SecurityGroupEgress:
        - CidrIp: 0.0.0.0/0
          IpProtocol: "-1"

  TargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      Name: !Sub "${AWS::StackName}-tg"
      Port: 80
      Protocol: HTTP
      VpcId: !Ref VpcId
      HealthCheckPath: /health
      TargetType: instance

  LaunchTemplate:
    Type: AWS::EC2::LaunchTemplate
    Properties:
      LaunchTemplateName: !Sub "${AWS::StackName}-lt"
      ImageId: !Ref AmiId
      InstanceType: !Ref InstanceType
      SecurityGroupIds:
        - !Ref InstanceSecurityGroup

  AutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      AutoScalingGroupName: !Sub "${AWS::StackName}-asg"
      MinSize: 2
      MaxSize: 10
      DesiredCapacity: 4
      LaunchTemplate:
        LaunchTemplateId: !Ref LaunchTemplate
        Version: !GetAtt LaunchTemplate.LatestVersionNumber
      VPCZoneIdentifier: !Ref SubnetIds
      TargetGroupARNs:
        - !Ref TargetGroup
      HealthCheckType: ELB
      HealthCheckGracePeriod: 300
      Tags:
        - Key: Name
          Value: !Sub "${AWS::StackName}-instance"
          PropagateAtLaunch: true

  ScalingPolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      PolicyName: !Sub "${AWS::StackName}-cpu-policy"
      PolicyType: TargetTrackingScaling
      AutoScalingGroupName: !Ref AutoScalingGroup
      TargetTrackingConfiguration:
        PredefinedMetricSpecification:
          PredefinedMetricType: ASGAverageCPUUtilization
        TargetValue: 70

Outputs:
  AutoScalingGroupName:
    Value: !Ref AutoScalingGroup
    Export:
      Name: !Sub "${AWS::StackName}-ASG-Name"

Validation Commands

Validate template and test changes before deployment:

# Validate CloudFormation template
aws cloudformation validate-template --template-body file://template.yaml