aws-cdk: (aws_rds): addRotationMultiUser secrets missing engine on bootstrap

Describe the bug

When I addRotationMultiUser with a DatabaseSecret,

const secret = new aws_rds.DatabaseSecret(this, 'Secret', {
  username: 'a_user_name',
  encryptionKey,
  secretName: 'aUserName',
  masterSecret: cluster.secret,
});
cluster.addRotationMultiUser('aUserName', { secret });

the rotation lambda fails with

[ERROR] KeyError: "Database engine must be set to 'postgres' in order to use this rotation lambda" Traceback (most recent call last):   File "/var/task/lambda_function.py", line 77, in lambda_handler     create_secret(service_client, arn, token)   File "/var/task/lambda_function.py", line 113, in create_secret     current_dict = get_secret_dict(service_client, arn, "AWSCURRENT")   File "/var/task/lambda_function.py", line 451, in get_secret_dict     raise KeyError("Database engine must be set to 'postgres' in order to use this rotation lambda")

Expected Behavior

It should work.

Current Behavior

It doesn’t work.

Reproduction Steps

import { App, Stack, StackProps, aws_ec2, aws_rds } from 'aws-cdk-lib';
import { Construct } from 'constructs';

export class MyStack extends Stack {
  constructor(scope: Construct, id: string, props: StackProps = {}) {
    super(scope, id, props);

    const vpc = aws_ec2.Vpc.fromLookup(this, 'VPC', {
      tags: { TheVpc: 'Default' }, // or whatever.
    });

    const cluster = new aws_rds.DatabaseCluster(this, 'MyCluster', {
      credentials: {
        username: 'manager',
      },
      engine: aws_rds.DatabaseClusterEngine.auroraPostgres({
        version: aws_rds.AuroraPostgresEngineVersion.VER_12_8,
      }),
      instanceProps: {
        instanceType: aws_ec2.InstanceType.of(
          aws_ec2.InstanceClass.T3,
          aws_ec2.InstanceSize.MEDIUM
        ),
        vpc,
      },
      instances: 1, // be cheap
    });
    cluster.addRotationSingleUser();

    const secret = new aws_rds.DatabaseSecret(this, 'ReaderSecret', {
      username: 'reader',
      masterSecret: cluster.secret,
    });

    cluster.addRotationMultiUser('ReaderRotation', { secret });
  }
}

// for development, use account/region from cdk cli
const devEnv = {
  account: process.env.CDK_DEFAULT_ACCOUNT,
  region: process.env.CDK_DEFAULT_REGION,
};

const app = new App();

new MyStack(app, 'my-stack-dev', { env: devEnv });

app.synth();

Chase down the substack for the multi-rotation, find the lambda, find it’s execution logs. Lo and behold, an error message appears!

Possible Solution

aws_rds.DatabaseSecret() should be bootstrapping the secret with basics from the masterSecret.

Additional Information/Context

No response

CDK CLI Version

2.18.0 (build 75c90fa)

Framework Version

same

Node.js Version

v16.13.1

OS

Darwin Kernel Version 21.2.0: Sun Nov 28 20:29:10 PST 2021; root:xnu-8019.61.5~1/RELEASE_ARM64_T8101 arm64

Language

Typescript

Language Version

"typescript": "^4.6.3"

Other information

No response