(aws-rds): Unable to use CfnParameter as port

[Lewenhaupt]

What is the problem?

CfnParameters cannot be used for the port value of a DatabaseInstance in aws-rds. The value requires only a number and valueAsNumber on a CfnParameter doesn't produce a valid number on synthesis.
"Port": "-1.8881545897088186e+289"
instead of
"ToPort": { "Ref": "DBPort" } (as it becomes for a security group)
https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_rds.DatabaseInstance.html

Reproduction Steps

const dbPort = new CfnParameter(this, 'DBPort', {
  type: 'Number',
  default: 5432
})

const postgresDb = new rds.DatabaseInstance(this, 'PostgresDb', {
      port: dbPort.valueAsNumber,
})

What did you expect to happen?

Expected that the generated cfn-template would have the port parameter as a reference to the cfn parameter

What actually happened?

The port parameter was set to a static value: -1.8881545897088186e+289

CDK CLI Version

2.0.0 (build 4b6ce31)

Framework Version

No response

Node.js Version

v16.9.1

OS

mac os

Language

Typescript

Language Version

No response

Other information

No response

[skinny85]

@ryparker you want to try and reproduce this one?

[ryparker]

Was able to reproduce this with the following code (using cdk ^1.135.0):

import { App, Stack, CfnParameter } from '@aws-cdk/core';
import { DatabaseInstance, DatabaseInstanceEngine } from '@aws-cdk/aws-rds';
import { Vpc, SubnetType } from '@aws-cdk/aws-ec2';


const app = new App();

const stack = new Stack(app, 'sampleRds', {
  env: {
    account: process.env.CDK_DEFAULT_ACCOUNT,
    region: process.env.CDK_DEFAULT_REGION
  }
});

const dbPort = new CfnParameter(stack, 'DBPort', {
  type: 'Number',
  default: 5432
})

const vpc = Vpc.fromLookup(stack, 'Vpc', {
  isDefault: true
})

const postgresDb = new DatabaseInstance(stack, 'PostgresDb', {
  port: dbPort.valueAsNumber,
  vpc,
  engine: DatabaseInstanceEngine.POSTGRES,
  vpcSubnets: {
    subnetType: SubnetType.PUBLIC
  }
})

CloudFormation output:

PostgresDb29EB1611:
    Type: AWS::RDS::DBInstance
    Properties:
      ...
      Port: "-1.888154589708827e+289"

[skinny85]

Thnx!

[jumic]

From my point of view, this is caused by props.port?.toString() in Instances.ts. We should replace it by Tokenization.stringifyNumber(props.port).

@skinny85 Are you working on it (because this issue is assigned to you)? If not, I can fix it and submit a PR.

[skinny85]

That would be awesome if you could work on this @jumic!

[github-actions]

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