咨询Autoscaling与Application-autoscaling的IAM策略差异

Great question! Let’s break down the key differences between IAM policies for EC2 Auto Scaling (often shorthanded to "Autoscaling") and Application Auto Scaling—they’re related but built for distinct use cases, and their IAM permissions reflect those differences clearly.

Core Service Targets #

First, it’s important to clarify what each service manages, since this drives their IAM requirements:

• EC2 Auto Scaling: Exclusively focused on managing EC2 Auto Scaling Groups (ASGs). This includes scaling EC2 instance counts, maintaining instance health, managing lifecycle hooks, and working with launch configurations/templates.
• Application Auto Scaling: A general-purpose scaling service that supports a wide range of non-EC2 AWS resources, like ECS services, Lambda function concurrency, DynamoDB tables/GSIs, ElastiCache clusters, SageMaker endpoints, and more. It acts as a centralized layer to automate scaling for these diverse resources.

IAM Action Prefixes #

The most obvious difference in IAM policies is the prefix used for permission actions:

• For EC2 Auto Scaling, all permissions use the autoscaling: prefix. Examples include:
  • autoscaling:UpdateAutoScalingGroup (adjust instance counts or settings)
  • autoscaling:DescribeAutoScalingGroups (view ASG details)
  • autoscaling:CreateLaunchTemplate (create templates for EC2 instances in ASGs)
• For Application Auto Scaling, actions use the application-autoscaling: prefix. Examples include:
  • application-autoscaling:RegisterScalableTarget (link a resource to Application Auto Scaling)
  • application-autoscaling:PutScalingPolicy (define scaling rules for a target resource)
  • application-autoscaling:DescribeScalingActivities (view scaling events for a target)

Resource ARN Formats #

The ARNs (Amazon Resource Names) referenced in policies also differ significantly, tied to the resources each service manages:

• EC2 Auto Scaling ARNs point directly to EC2-specific scaling resources. For an Auto Scaling Group, the ARN looks like:

  arn:aws:autoscaling:us-east-1:123456789012:autoScalingGroup:abc123-def456-ghi789-jkl012:autoScalingGroupName/MyProductionASG
  

• Application Auto Scaling ARNs are structured to link to the specific scalable target resource. The format varies by the underlying service. For example:
  • ECS service scalable target ARN:

    arn:aws:application-autoscaling:us-east-1:123456789012:scalable-target/service/ecs/MyCluster/MyWebService
    

  • DynamoDB table scalable target ARN:

    arn:aws:application-autoscaling:us-east-1:123456789012:scalable-target/table/MyUserTable
    

Common Permission Scenarios #

The permissions you’ll grant depend entirely on which service you’re working with:

• If you need a role to adjust the size of an EC2 ASG, you’d grant autoscaling:UpdateAutoScalingGroup with the ARN of the target ASG as the resource.
• If you need a role to scale an ECS service, you’d grant application-autoscaling:PutScalingPolicy and application-autoscaling:RegisterScalableTarget (with the ECS scalable target ARN), plus additional permissions like ecs:UpdateService—since Application Auto Scaling needs to call the underlying ECS API to execute scaling actions.

Condition Key Differences #

Both services support tag-based access control, but their condition keys use different prefixes:

• EC2 Auto Scaling uses keys like autoscaling:ResourceTag/Environment to restrict access based on ASG tags.
• Application Auto Scaling uses keys like application-autoscaling:ResourceTag/Team for the same purpose on its scalable targets. Additionally, you may need to combine these with condition keys from the underlying service (e.g., ecs:ResourceTag/Environment for ECS targets) for full access control.

Quick Summary #

To boil it down:

• EC2 Auto Scaling IAM policies are purpose-built for managing EC2 instance groups, with autoscaling: actions and EC2-specific ARNs.
• Application Auto Scaling policies are a general framework for scaling non-EC2 resources, using application-autoscaling: actions and resource-specific ARNs tied to services like ECS or DynamoDB.

You can’t mix these permissions—an autoscaling: action won’t work for Application Auto Scaling targets, and vice versa.

内容的提问来源于stack exchange，提问作者shiv455