aws_route53: cannot use CfnParameter.valueAsNumber for L2 RecordSet weight

[nicholaschiasson]

Describe the bug

Cannot construct ARecord (and presumably any RecordSet) with weight resolved by CfnParameter value.

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

No response

Expected Behavior

RecordSet should successfully be synthesized with the parameter's token value for the weight.

Current Behavior

Synthesis fails, token value representing a number outside the bounds of a valid weight (0-255).

Error: weight must be between 0 and 255 inclusive, got: -1.888154589708757e+289
    at new RecordSet (/.../node_modules/aws-cdk-lib/aws-route53/lib/record-set.js:1:3296)
    at new ARecord (/.../node_modules/aws-cdk-lib/aws-route53/lib/record-set.js:1:7665)
    ...

Reproduction Steps

import { aws_route53 as r53, CfnParameter } from 'aws-cdk-lib';

const weightParameter: CfnParameter = new CfnParameter(this, 'Weight', {
  default: 0,
  maxValue: 255,
  minValue: 0,
  type: 'Number'
});

const zone = r53.HostedZone.fromLookup(this, 'HostedZone', {
  domainName: 'example.com'
});

const aRecord = new r53.ARecord(this, 'ARecord', {
  weight: weightParameter.valueAsNumber,
  zone
});

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.151.0 (build b8289e2)

Framework Version

No response

Node.js Version

v20.13.1

OS

Linux 5.15.153.1-microsoft-standard-WSL2 #1 SMP Fri Mar 29 23:14:13 UTC 2024 x86_64 x86_64 GNU/Linux

Language

TypeScript

Language Version

No response

Other information

Currently using this workaround:

...

const aRecord = new r53.ARecord(this, 'ARecord', {
  weight: 0,
  zone
});

(aRecord.node.defaultChild as r53.CfnRecordSet).addPropertyOverride('Weight', weightParameter.valueAsNumber);

[ashishdhingra]

@nicholaschiasson Good afternoon. Thanks for opening the issue. Issue is reproducible using below code:

import * as cdk from 'aws-cdk-lib';
import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as r53 from 'aws-cdk-lib/aws-route53';
import * as r53targets from 'aws-cdk-lib/aws-route53-targets';
import { ApplicationLoadBalancer } from 'aws-cdk-lib/aws-elasticloadbalancingv2';


export class CdktestStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const domainName = 'example.com';
    const vpc = ec2.Vpc.fromLookup(this, 'DefaultVpc', { isDefault: true });
    const weightParameter = new cdk.CfnParameter(this, 'Weight', {
      default: 0,
      maxValue: 255,
      minValue: 0,
      type: 'Number'
    });
    
    const zone = r53.HostedZone.fromLookup(this, 'HostedZone', {
      domainName: 'example.com'
    });
    
    const loadBalancer = new ApplicationLoadBalancer(this, 'ServiceLB', {
      vpc,
      internetFacing: true
    });
    const serviceSG = new ec2.SecurityGroup(this, 'ServiceSecurityGroup', { vpc });
    serviceSG.connections.allowFrom(loadBalancer, ec2.Port.tcp(80));
    console.log(`${weightParameter}`);
    const aRecord = new r53.ARecord(this, 'ARecord', {
      target: r53.RecordTarget.fromAlias(new r53targets.LoadBalancerTarget(loadBalancer)),
      weight: weightParameter.valueAsNumber,
      zone
    });
  }
}

However, although AWS CloudFormation parameters can be defined in the AWS CDK, they are generally discouraged because AWS CloudFormation parameters are resolved only during deployment. This means that you cannot determine their value in your code. Because the AWS CDK takes an approach where concrete templates are resolved at synthesis time and so is the validation in this case, the alternative approach is to use context values either from the command line or via the cdk.json. Refer Parameters and the AWS CDK for details.

So in your use case, you could modify your code as below:

...
const weight = this.node.tryGetContext('Weight');
    
const aRecord = new r53.ARecord(this, 'ARecord', {
  ...,
  weight: Number.parseInt(weight),
  zone
});

and run cdk synth -c Weight=20 as an example.

Thanks,
Ashish

[nicholaschiasson]

Hi @ashishdhingra , thanks for your quick response.

I'm aware of parameters being discouraged in favour of context arguments. Still, I consider this an unexpected behaviour and for my use case, I strongly prefer the use of a CFN parameter for this.

Here are some similar issues I was able to find which have been stated this behaviour is a bug, and which have been resolved: #7126 #9038

I imagine the fix should be similar to the fixes for those issues as well: #8252 #9176

Indeed, in the current HEAD on main branch, I see the weight property is not being validated as a Token.

I will try to open a PR to resolve this since it looks to be a simple fix.

[badmintoncryer]

@nicholaschiasson I've implemented this validation and this is my fault for not checking whether weight is token or not. I would greatly appreciate it if you could create a PR.