Aws-cdk: Add support for AWS::CloudFormation::Init

[taichi]

TypeScript CDK 0.9.2

How to write AWS::CloudFormation::Init metadata with AWS Construct Library for cfn-init ?
I want to add AWS::CloudFormation::Init metadata to AutoScalingGroup.

[rix0rrr]

We don't have this modeled as an L2 right now.

You can instantiate a cdk.Resource and pass in the properties that make up an Init resource, and add the appropriate call to the ASGs userData yourself.

[rix0rrr]

It should include support for environment variables, by writing them to a script in /etc/profile.d.

Need to do research to see if all ways of starting a program source the files there well enough.

[taichi]

I'm trying to convert this template with cdk.
atlassian-aws-deployment / templates / JiraDataCenter.template.yaml

environment variables are in l.1008

[0xdevalias]

Any updates/likely merge time on https://github.com/awslabs/aws-cdk/pull/792 , or at least a worked example of how to add AWS::CloudFormation::Init to an autoscaling.AutoScalingGroup?

• https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-init.html
• https://awslabs.github.io/aws-cdk/refs/_aws-cdk_aws-autoscaling.html#auto-scaling-group

The following template shows that it should be added to the AWS::AutoScaling::LaunchConfiguration in the CloudFormation:

• https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/example-templates-autoscaling.html

I see that https://github.com/awslabs/aws-cdk/issues/606 makes reference to being able to find/modify children since 0.10.0. Following the syntax there.. it looks like the following should work for us..:

// Ref: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-init.html
// Ref: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/example-templates-autoscaling.html
const asgLaunchConfig = asg.findChild('LaunchConfig') as autoscaling.cloudformation.LaunchConfigurationResource;
asgLaunchConfig.addOverride("Metadata", {
    "AWS::CloudFormation::Init": {
        "FOO": "BAR",
    }
});

Running cdk synth, I get the following, which implies it is working as expected:

AutoScalingGroupLaunchConfigDEEB160C:
  Type: 'AWS::AutoScaling::LaunchConfiguration'
  ..snip..
  Metadata:
      'AWS::CloudFormation::Init':
          FOO: BAR

[eladb]

Closed PR for now. Reopen as needed.

[0xdevalias]

Sad that that PR didn’t land.. :(

[eladb]

We'll get there. It's an important feature... Just got too much on our table RN...
Happy to take contributions of course if you are interested to pick it up

[eladb]

Still relevant

[brettswift]

I haven't taken a stab at an L2 construct, but I put together a template I might be able to refactor out into something easier. I needed a shell script to be put onto the machine and be executed. The construct for Init will hopefully make it easier to "just execute this script at launch time". So I have scoped my solution to just the file / command resources, and a little bit of a fairly robust userdata script (that requires the ASG and Launch config for both cfn-init and cfn-signal).

I put it up on a gist instead of here. Hopefully this is helpful if someone writes the L2, to see how I tackled this use case. I'd like to spend time on an L2 but not sure I'll have the time for a while.

https://gist.github.com/brettswift/6e48a70d808a28614438520682459f0c

[brettswift]

I updated the gist above adding in a builder class to help us reduce code re-use. Definitely not feature complete for cfn-init, however it's one take to solve just our use case still. If this is a strategy that people like, I might have time to contribute to a PR into CDK.

[ywauto83]

any update on this? @rix0rrr

[robertd]

Yeah, I'd really like to see this feature ship soon. Using escape hatches to accomplish this task is very cumbersome.

[Zirkonium88]

Please, keep things going on this @rix0rrr

[Zirkonium88]

With regard to another issue about adding metadata, this seems to be a work around at the moment: Modifying the AWS CloudFormation resource behind AWS constructs

[oscarnevarezleal]

I saw this is documented on the AWS CDK API under Configuring Instances using CloudFormation Init (cfn-init)
but it doesn't seem to work ( _undefined init property on instanceProps_ ) in version @1.60.0