What is Amazon EC2 Auto Scaling? - Amazon EC2 Auto Scaling
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China.

What is Amazon EC2 Auto Scaling?

Amazon EC2 Auto Scaling helps you ensure that you have the correct number of Amazon EC2 instances available to handle the load for your application. You create collections of EC2 instances, called Auto Scaling groups. You can specify the minimum number of instances in each Auto Scaling group, and Amazon EC2 Auto Scaling ensures that your group never goes below this size. You can specify the maximum number of instances in each Auto Scaling group, and Amazon EC2 Auto Scaling ensures that your group never goes above this size. If you specify the desired capacity, either when you create the group or at any time thereafter, Amazon EC2 Auto Scaling ensures that your group has this many instances. If you specify scaling policies, then Amazon EC2 Auto Scaling can launch or terminate instances as demand on your application increases or decreases.

For example, the following Auto Scaling group has a minimum size of one instance, a desired capacity of two instances, and a maximum size of four instances. The scaling policies that you define adjust the number of instances, within your minimum and maximum number of instances, based on the criteria that you specify.


			An illustration of a basic Auto Scaling group.

For more information about the benefits of Amazon EC2 Auto Scaling, see Amazon EC2 Auto Scaling benefits.

Auto Scaling components

The following table describes the key components of Amazon EC2 Auto Scaling.


									A graphic representing an Auto Scaling group.

Groups

Your EC2 instances are organized into groups so that they can be treated as a logical unit for the purposes of scaling and management. When you create a group, you can specify its minimum, maximum, and, desired number of EC2 instances. For more information, see Auto Scaling groups.


									A graphic representing a launch template or launch
										configuration.

Configuration templates

Your group uses a launch template, or a launch configuration (not recommended, offers fewer features), as a configuration template for its EC2 instances. You can specify information such as the AMI ID, instance type, key pair, security groups, and block device mapping for your instances. For more information, see Launch templates and Launch configurations.


									A graphic representing scaling options.

Scaling options

Amazon EC2 Auto Scaling provides several ways for you to scale your Auto Scaling groups. For example, you can configure a group to scale based on the occurrence of specified conditions (dynamic scaling) or on a schedule. For more information, see Scaling options.

Pricing for Amazon EC2 Auto Scaling

There are no additional fees with Amazon EC2 Auto Scaling, so it's easy to try it out and see how it can benefit your Amazon architecture. You only pay for the Amazon resources (for example, EC2 instances, EBS volumes, and CloudWatch alarms) that you use.

Get started

To begin, complete the Get started with Amazon EC2 Auto Scaling tutorial to create an Auto Scaling group and see how it responds when an instance in that group terminates.

To automatically distribute incoming application traffic across multiple instances in your Auto Scaling group, use Elastic Load Balancing. For more information, see Use Elastic Load Balancing to distribute traffic across the instances in your Auto Scaling group.

To monitor your Auto Scaling groups and instance utilization data, use Amazon CloudWatch. For more information, see Monitor CloudWatch metrics for your Auto Scaling groups and instances.

To configure auto scaling for scalable resources for Amazon Web Services beyond Amazon EC2, see the Application Auto Scaling User Guide.

Work with Auto Scaling groups

You can create, access, and manage your Auto Scaling groups using any of the following interfaces:

  • Amazon Web Services Management Console – Provides a web interface that you can use to access your Auto Scaling groups. If you've signed up for an Amazon Web Services account, you can access your Auto Scaling groups by signing into the Amazon Web Services Management Console, using the search box on the navigation bar to search for Auto Scaling groups, and then choosing Auto Scaling groups.

  • Amazon Command Line Interface (Amazon CLI) – Provides commands for a broad set of Amazon Web Services, and is supported on Windows, macOS, and Linux. To get started, see Amazon Command Line Interface User Guide. For more information, see autoscaling in the Amazon CLI Command Reference.

  • Amazon Tools for Windows PowerShell – Provides commands for a broad set of Amazon products for those who script in the PowerShell environment. To get started, see the Amazon Tools for Windows PowerShell User Guide. For more information, see the Amazon Tools for PowerShell Cmdlet Reference.

  • Amazon SDKs – Provides language-specific API operations and takes care of many of the connection details, such as calculating signatures, handling request retries, and handling errors. For more information, see Amazon SDKs.

  • Query API – Provides low-level API actions that you call using HTTPS requests. Using the Query API is the most direct way to access Amazon Web Services. However, it requires your application to handle low-level details such as generating the hash to sign the request, and handling errors. For more information, see the Amazon EC2 Auto Scaling API Reference.

  • Amazon CloudFormation – Supports creating Auto Scaling groups using CloudFormation templates. For more information, see Create Auto Scaling groups with Amazon CloudFormation.

To connect programmatically to an Amazon Web Service, you use an endpoint. For information about endpoints for calls to Amazon EC2 Auto Scaling, see Endpoints and ARNs for Amazon Web Services in China in the Getting Started with Amazon Web Services in China.