feat(core): Customizable class for L1 constructs customization

[pahud]

Describe the feature

We have seen many cases that users are trying to customize some properties for resources generated by CDK behind L2 constructs and it's not easy to achieve that. I was thinking we probably should propose something like the Tags class that builds a Aspect under the hood and iterates the constructs tree for users without having to write the Aspect by themselves.

Use Case

1. Customize all CustomResource ServiceTimeout behind a specific construct. This PR would allow CustomResource L2 to support ServiceTimeout but for those custom resources created by L2s behind the scene, users would not be able to customize their ServiceTimeouts.

2. Customize the LoggingConfig of all lambda.Function, including those created by CDK for custom resource providers as described in feat(custom-resource): universal loggingConfig for all custom resource providers #30777.

Proposed Solution

We probably could have a Customizable class just like the Tags class and the API experience would be like:

// make all custom resource behind this scope a 1200 seconds timeout as default
Customizable.of(this).add('AWS::CloudFormation::CustomResource', 'ServiceTimeout', 1200);

// search all custom resources behind this scope, and run user-provided callback function against all of them
Customizable.of(this).bind('AWS::CloudFormation::CustomResource', cb);

// all lambda.Function should have a default LoggingConfig defined, only apply if undefined
Customizable.of(this).add('AWS::Lambda::Function', 'LoggingConfig', myconfig, { overrideIfUndefined: true });

// iterate all lambda.Functions with a custom callback method. In this `cb` function, we can check if `LoggingConfig` is defined, and override the LoggingConfig.LogGroup when necessary.
Customizable.of(this).bind('AWS::Lambda::Function', cb);

Sample

export class Customizable {
    private static readonly customizations: { [key: string]: any } = {};
  
    static of(scope: Construct): Customizable {
      return new Customizable(scope);
    }
  
    private constructor(private readonly scope: Construct) {}
  
    add(resourceType: string, propertyName: string, value: any): void {
      const key = `${resourceType}/${propertyName}`;
      Customizable.customizations[key] = value;
      this.applyCustomizations(resourceType, propertyName);
    }
  
    private applyCustomizations(resourceType: string, propertyName: string): void {
      const constructs = this.scope.node.findAll();
      this.applyCustomizationsRecursively(resourceType, propertyName, constructs);
    }
  
    private applyCustomizationsRecursively(resourceType: string, propertyName: string, constructs: IConstruct[]): void {
      constructs.forEach(c => {
        if (CfnResource.isCfnResource(c)) {
          if (c.cfnResourceType === resourceType) {
            const customization = Customizable.getCustomization(c, propertyName);
            if (customization) {
              c.addPropertyOverride(propertyName, customization);
            }
          } else {
            // it's a CfnResource but not the resource type we need
            // console.log('skipping ' +  c.cfnResourceType)
          }
        } else {
          // if it's not a cfnResource it has to be a construct
          this.applyCustomizationsRecursively(resourceType, propertyName, c.node.children);
        }
      });
    }
  
    static getCustomization(resource: CfnResource, propertyName: string): any {
      const key = `${resource.cfnResourceType}/${propertyName}`;
      return Customizable.customizations[key];
    }
  }
  

• override the LoggingConfig for all custom resources behind this stack:

new eks.Cluster(this, 'Cluster', {
    version: eks.KubernetesVersion.V1_30,
  });

  // create a shared log group
  this.lambdaSharedLogGroup = new logs.LogGroup(this, id, {
    retention: logs.RetentionDays.NINE_YEARS,
  });

  Customizable.of(this).add('AWS::Lambda::Function', 'LoggingConfig', {
    LogGroup: this.lambdaSharedLogGroup.logGroupName,
  });

• override the VisibilityTimeout for all sqs queues behind this scope:

Customizable.of(this).add('AWS::SQS::Queue', 'VisibilityTimeout', 300);

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.148.0

Environment details (OS name and version, etc.)

all