Aws-cdk: ec2: cfn-init support in ASGs

[cohalz]

I want to use the logical ID of the resource created in the construct library.
For example, cfn-signal require AutoScalingGroup's logical id.

I wrote this code.

    const asg = cluster.addDefaultAutoScalingGroupCapacity({
      instanceType: new ec2.InstanceType("t2.xlarge"),
      instanceCount: 1,
    });

    const appLaunchTemplate = new ec2.cloudformation.LaunchTemplateResource(this, 'AppLaunchTemplate', {
      launchTemplateName: "launchtemplatetest",
      launchTemplateData: {
        userData: new cdk.FnBase64([
            `#!/bin/sh`,
            `set -e`,
            `echo ECS_CLUSTER=${cluster.clusterName} >> /etc/ecs/ecs.config`,
            `/opt/aws/bin/cfn-signal -e $? --stack ${new cdk.AwsStackName()} --resource ${asg.autoScalingGroupName} --region ${new cdk.AwsRegion}`,
          ].join('\n')
        ),
      }
    })
    appLaunchTemplate.addDependency(instanceProfile)

    const asgResource = asg.findChild('ASG') as autoscaling.cloudformation.AutoScalingGroupResource

    asgResource.addPropertyDeletionOverride('LaunchConfigurationName')
    asgResource.addPropertyOverride('LaunchTemplate', {
      LaunchTemplateId: appLaunchTemplate.ref,
      Version: '1'
    })

However Circular dependency caused.

    SampleStack failed: ValidationError: Circular dependency between resources: [AppLaunchTemplate, ClusterDefaultAutoScalingGroupLifecycleHookDrainHook4A9A4325, ClusterDefaultAutoScalingGroupASG0F98E147]
Circular dependency between resources: [AppLaunchTemplate, ClusterDefaultAutoScalingGroupLifecycleHookDrainHook4A9A4325, ClusterDefaultAutoScalingGroupASG0F98E147]

This will be solved by specifying a name or not have a hash in construct library.

[eladb]

To to make sure I understand the problem: asg.autoScalingGroupName is not the logical ID but rather a the actual name of the ASG, resolved only at deploy-time, and that's the reason we are getting the cyclic dependency, correct?

What you could do is simply use asgResource.logicalId instead of asg.autoScalingGroupName:

`/opt/aws/bin/cfn-signal -e $? --stack ${new cdk.AwsStackName()} --resource ${asgResource.logicalId} --region ${new cdk.AwsRegion}`,

As for a longer term solution, I am not sure this is actually a very common need in the general sense, but perhaps we can provide a nice abstract to 'cfn-signal' so you could do something like:

asg.cfnSignal({ options });

And it will return the "correct" cfn-signal command bound to this specific ASG.

[cohalz]

thanks a lot, did the expected behavior with asgResource.logicalId🙇‍♂️

[eladb]

I will keep this open (and change title) so we can use this as an example for the cfn-init support, okay?

[cohalz]

okay, thanks.

[otterley]

Related: #777

[SanderKnape]

It seems that logicalId is no longer a property for resources. @eladb what is the current method to fetch the logical ID? It need it for the same purpose as the OP.

[eladb]

https://docs.aws.amazon.com/cdk/api/latest/docs/@aws-cdk_core.CfnResource.html#logicalid

[SanderKnape]

For future reference, this is how you can get the logical ID for the autoscaling group:

const autoScalingGroupCfn = <CfnAutoScalingGroup> autoscalingGroup.node.tryFindChild('ASG');
console.log(autoScalingGroupCfn.logicalId);

[andreclaro]

Hello, any workaround to make cfn-init (AWS::CloudFormation::Init:) work with CDK?

Is there a way to add the CloudFormation directly when CDK does not support a feature like this?

[rix0rrr]

Related to https://github.com/aws/aws-cdk/issues/777