Auto Scaling

Overview

CloudMock emulates Amazon EC2 Auto Scaling, supporting launch configurations, auto scaling groups with min/max/desired capacity enforcement, scaling policies (Simple, Step, and Target Tracking), scheduled actions, lifecycle hooks, metrics collection, and instance lifecycle operations.

Supported Operations

Operation	Status	Notes
CreateLaunchConfiguration	Supported
DescribeLaunchConfigurations	Supported
DeleteLaunchConfiguration	Supported
CreateAutoScalingGroup	Supported	Enforces min/max/desired capacity
DescribeAutoScalingGroups	Supported
UpdateAutoScalingGroup	Supported
DeleteAutoScalingGroup	Supported
SetDesiredCapacity	Supported	Clamped to min/max
DescribeAutoScalingInstances	Supported
AttachInstances	Supported
DetachInstances	Supported
PutScalingPolicy	Supported	SimpleScaling, StepScaling, TargetTrackingScaling
DescribePolicies	Supported	Filter by ASG name or policy names
DeletePolicy	Supported
ExecutePolicy	Supported	Applies scaling adjustment; clamps to min/max
PutScheduledUpdateGroupAction	Supported	Cron-based scheduled scaling
DescribeScheduledActions	Supported	Filter by ASG name
DeleteScheduledAction	Supported
EnableMetricsCollection	Supported	No-op acknowledgment in mock
DisableMetricsCollection	Supported	No-op acknowledgment in mock
PutLifecycleHook	Supported	LAUNCHING and TERMINATING transitions
DescribeLifecycleHooks	Supported	Filter by ASG name or hook names
DeleteLifecycleHook	Supported
CompleteLifecycleAction	Supported	No-op (lifecycle completion acknowledged)
CreateOrUpdateTags	Supported
DescribeTags	Supported
DeleteTags	Supported

Quick Start

Node.js

import {
  AutoScalingClient,
  CreateLaunchConfigurationCommand,
  CreateAutoScalingGroupCommand,
  PutScalingPolicyCommand,
  PutLifecycleHookCommand,
} from '@aws-sdk/client-auto-scaling';

const client = new AutoScalingClient({
  endpoint: 'http://localhost:4566',
  region: 'us-east-1',
  credentials: { accessKeyId: 'test', secretAccessKey: 'test' },
});

await client.send(new CreateLaunchConfigurationCommand({
  LaunchConfigurationName: 'my-lc',
  ImageId: 'ami-12345678',
  InstanceType: 't3.micro',
}));

await client.send(new CreateAutoScalingGroupCommand({
  AutoScalingGroupName: 'my-asg',
  LaunchConfigurationName: 'my-lc',
  MinSize: 1,
  MaxSize: 5,
  DesiredCapacity: 2,
  AvailabilityZones: ['us-east-1a'],
}));

await client.send(new PutLifecycleHookCommand({
  AutoScalingGroupName: 'my-asg',
  LifecycleHookName: 'launch-hook',
  LifecycleTransition: 'autoscaling:EC2_INSTANCE_LAUNCHING',
  DefaultResult: 'CONTINUE',
  HeartbeatTimeout: 300,
}));

Python

import boto3

client = boto3.client('autoscaling',
    endpoint_url='http://localhost:4566',
    region_name='us-east-1',
    aws_access_key_id='test',
    aws_secret_access_key='test')

client.create_launch_configuration(
    LaunchConfigurationName='my-lc',
    ImageId='ami-12345678',
    InstanceType='t3.micro')

client.create_auto_scaling_group(
    AutoScalingGroupName='my-asg',
    LaunchConfigurationName='my-lc',
    MinSize=1, MaxSize=5, DesiredCapacity=2,
    AvailabilityZones=['us-east-1a'])

client.put_scheduled_update_group_action(
    AutoScalingGroupName='my-asg',
    ScheduledActionName='nightly-scale-down',
    DesiredCapacity=1,
    Recurrence='0 2 * * *')

Configuration

cloudmock.yml

services:
  autoscaling:
    enabled: true

Known Differences from AWS

• Scaling policies are stored but automatic metric-based scaling is not performed
• ExecutePolicy applies the adjustment once on demand
• Lifecycle hooks are stored but do not intercept actual instance launch/termination
• EnableMetricsCollection/DisableMetricsCollection are no-ops (acknowledged, not enforced)
• Instance reconciliation is simulated and does not launch real EC2 instances