aws-autoscaling: LaunchTemplate resource should be created for AutoScalingGroup instead of LaunchConfiguration when running unit tests

[carlosahs]

Describe the bug

Hi, template generated from stack in unit tests creates a LaunchConfiguration resource instead of the recommended LaunchTemplate resource when an AutoScalingGroup resource is created. So when a test like this is added:

test('Auto Scaling Group Created', () => {
    const app = new App();
    const stack = new DummyStack(app, 'DummyStack');
    const template = Template.fromStack(stack);
    console.log(template);
    template.hasResourceProperties('AWS::AutoScaling::AutoScalingGroup', {
        AutoScalingGroupName: 'MyAutoScalingGroup',
        LaunchTemplate: Match.anyValue(),
        MaxSize: '1',
        MinSize: '0'
    });
});

It will fail with:

 FAIL  test/dummy.test.ts
  ✕ Auto Scaling Group Created (213 ms)

  ● Auto Scaling Group Created

    Template has 1 resources with type AWS::AutoScaling::AutoScalingGroup, but none match as expected.
    The 1 closest matches:
    MyAutoScalingGroupASG1686ADA7 :: {
      "Properties": {
        "LaunchConfigurationName": { "Ref": "MyAutoScalingGroupLaunchConfig15D8856B" },
    !!   Missing key 'LaunchTemplate'
        "LaunchTemplate": undefined,
        "MaxSize": "1",
        "MinSize": "0",
        "Tags": [ { ... } ],
        "VPCZoneIdentifier": [ ... ]
      },
      "Type": "AWS::AutoScaling::AutoScalingGroup",
      "UpdatePolicy": { "AutoScalingScheduledAction": { "IgnoreUnmodifiedGroupSizeProperties": true } }
    }

Please note that this only happens for unit tests, when cdk synth is executed AutoScalingGroup is correctly created with a LaunchTemplate:

"MyAutoScalingGroupASG1686ADA7": {
 "Type": "AWS::AutoScaling::AutoScalingGroup",
 "Properties": {
  "AutoScalingGroupName": "MyAutoScalingGroup",
  "LaunchTemplate": {
   "LaunchTemplateId": {
    "Ref": "MyAutoScalingGroupLaunchTemplate9D9A040D"
   },
   "Version": {
    "Fn::GetAtt": [
     "MyAutoScalingGroupLaunchTemplate9D9A040D",
     "LatestVersionNumber"
    ]
   }
  },
  ...
}

Expected Behavior

LaunchTemplate should be created instead of LaunchConfiguration for AutoScalingGroup when template is created during unit test execution. This as per recommendation of Template reference docs.

Current Behavior

LaunchConfiguration is created for AutoScalingGroup instead of LaunchTemplate when template is created during unit test execution. This is against recommendation of Template reference docs.

Reproduction Steps

1. Create a new CDK app with cdk init app --language typescript using latest CDK CLI (version 2.121.1 (build d86bb1a)).
2. Update stack in lib/ with this code:

export class DummyStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);
    const vpc = new ec2.Vpc(this, 'CoreVpc', {
      availabilityZones: ['us-east-1a', 'us-east-1b'],
      enableDnsHostnames: false,
      enableDnsSupport: false,
      ipAddresses: ec2.IpAddresses.cidr('10.0.0.0/16'),
      subnetConfiguration: [
          {
              cidrMask: 20,
              name: 'private',
              subnetType: ec2.SubnetType.PRIVATE_ISOLATED
          }
      ],
      vpcName: 'MyVpc'
  });
    const autoScalingGroup = new autoscaling.AutoScalingGroup(this, 'MyAutoScalingGroup', {
      autoScalingGroupName: 'MyAutoScalingGroup',
      instanceType: new ec2.InstanceType('t2.micro'),
      machineImage: ecs.EcsOptimizedImage.amazonLinux2(),
      maxCapacity: 1,
      minCapacity: 0,
      vpc: vpc,
    });
  }
}

3. Update test file in test/ with this code:

test('Auto Scaling Group Created', () => {
  const app = new App();
  const stack = new DummyStack(app, 'DummyStack');
  const template = Template.fromStack(stack);
  console.log(template);
  template.hasResourceProperties('AWS::AutoScaling::AutoScalingGroup', {
    LaunchTemplate: Match.anyValue(),
    MaxSize: '1',
    MinSize: '0'
  });
});

4. Run npm test.

Possible Solution

Possibly solution from #23165 could be extended.

Additional Information/Context

Contents from package.json:

{
  "name": "dummy",
  "version": "0.1.0",
  "bin": {
    "dummy": "bin/dummy.js"
  },
  "scripts": {
    "build": "tsc",
    "watch": "tsc -w",
    "test": "jest",
    "cdk": "cdk"
  },
  "devDependencies": {
    "@types/jest": "^29.5.11",
    "@types/node": "20.10.8",
    "jest": "^29.7.0",
    "ts-jest": "^29.1.1",
    "aws-cdk": "2.121.1",
    "ts-node": "^10.9.2",
    "typescript": "~5.3.3"
  },
  "dependencies": {
    "aws-cdk-lib": "2.121.1",
    "constructs": "^10.0.0",
    "source-map-support": "^0.5.21"
  }
}

CDK CLI Version

2.121.1 (build d86bb1a)

Framework Version

2.121.1

Node.js Version

v18.18.0

OS

macOS Sonoma 14.2.1

Language

TypeScript

Language Version

Version 5.3.3

Other information

• aws-autoscaling: Use launch templates instead of deprecated launch configurations #23165

[pahud]

I guess it's to avoid breaking changes. The LT will not be created by default only when prop.launchTemplate is defauled

aws-cdk/packages/aws-cdk-lib/aws-autoscaling/lib/auto-scaling-group.ts

Line 1305 in 20ad55e

if (props.launchTemplate || props.mixedInstancesPolicy) {

or AUTOSCALING_GENERATE_LAUNCH_TEMPLATE is enabled

https://github.com/aws/aws-cdk/blob/20ad55e7aec7d387550db865257dc6f8ebcab067/packages/aws-cdk-lib/aws-autoscaling/lib/auto-scaling-group.ts#L1365C43-L1365C79

[github-actions]

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[carlosahs]

But how is it that with cdk synth LT is created and not when unit tests are executed with npm test? If I use launchTemplate prop I need to make sure I specify ImageId with an ECS optimized AMI and make sure UserData contains this script (which is automatically generated when I run cdk synth without needing to specify launchTemplate prop with reproduction steps code above):

#!/bin/bash
echo ECS_CLUSTER=<ecs-cluster-logical-id> >> /etc/ecs/ecs.config
sudo iptables --insert FORWARD 1 --in-interface docker+ --destination 169.254.169.254/32 --jump DROP
sudo service iptables save
echo ECS_AWSVPC_BLOCK_IMDS=true >> /etc/ecs/ecs.config

Concern here is that what cdk synth generates is not consistent with what is generated when npm test is run, which makes unit tests less reliable.