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.

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.

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.

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.

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 AWS architecture. You only pay for the AWS 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.

Related services

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:

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

• AWS Command Line Interface (AWS CLI) – Provides commands
  for a broad set of AWS services, and is supported on Windows, macOS, and
  Linux. To get started, see Prepare to use the AWS CLI. For more information, see autoscaling in the AWS CLI Command Reference.

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

• AWS 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 AWS 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 AWS 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.

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

To connect programmatically to an AWS service, you use an endpoint. For information
about endpoints for calls to Amazon EC2 Auto Scaling, see Amazon EC2 Auto Scaling endpoints and
quotas in the AWS General Reference.