Read Stack Outputs

A stack output is a value a stack publishes after it is deployed, such as a bucket's ARN or an API's URL. You declare one with a CDK CfnOutput. With cdkd it works as it does with CloudFormation: the value is resolved during the deploy and printed at the end.

The one difference is where the value is kept afterwards. CloudFormation keeps outputs on the stack. cdkd keeps them in the stack's state, the JSON file in S3 where it records what it deployed.

Declare, deploy, read

Declare the output in your CDK code as usual:

new cdk.CfnOutput(this, 'BucketArn', {
  value: bucket.bucketArn,
  description: 'ARN of the bucket',
});

cdkd deploy resolves the value and prints it after the deployment summary, in the format the AWS CDK CLI uses:

Outputs:
  MyStack.BucketArn = arn:aws:s3:::actual-bucket-name-xyz

✓ Deployment completed successfully

cdkd also saves the value under outputs in the stack's state file:

{
  "outputs": {
    "BucketArn": "arn:aws:s3:::actual-bucket-name-xyz"
  }
}

You can read it back later, from any directory and without the CDK app:

cdkd state show MyStack          # outputs and resources, human-readable
cdkd state show MyStack --json   # the whole record, for a script

Differences from CloudFormation

The state file for MyStack in us-east-1 is at s3://<bucket>/cdkd/MyStack/us-east-1/state.json.

Secrets in outputs are masked

cdkd does not write a secret into an output. It stores and prints *** when the output's value comes from one of these:

• a NoEcho parameter,
• a {{resolve:...}} reference to a secret,
• a NoEcho attribute of a custom resource.

This affects a stack that reads such an output from another stack. The reading stack gets the real value only when both stacks are deployed in the same cdkd deploy run. An output is published data, so keep secrets out of outputs.

Related

• Use Another Stack's Outputs: using another stack's outputs
• State Store: the state file that holds them
• cdkd state: cdkd state show and its flags