如何为 Cloudfront 创建 HttpOrigin 以使用 Lambda function url？

Question

Trying to setup a Cloudfront behaviour to use a Lambda function url with code like this:

    this.distribution = new Distribution(this, id + "Distro", {
      comment: id + "Distro",
      defaultBehavior: {
        origin: new S3Origin(s3Site),
        viewerProtocolPolicy: ViewerProtocolPolicy.REDIRECT_TO_HTTPS,
      },
      additionalBehaviors: {
        [`api-prd-v2/*`]: {
          compress: true,
          originRequestPolicy: originRequestPolicy,
          origin: new HttpOrigin(functionUrl.url, {
            protocolPolicy: OriginProtocolPolicy.HTTPS_ONLY,
            originSslProtocols: [OriginSslPolicy.TLS_V1_2],
          }),
          allowedMethods: AllowedMethods.ALLOW_ALL,
          viewerProtocolPolicy: ViewerProtocolPolicy.HTTPS_ONLY,
          cachePolicy: apiCachePolicy,
        },

The functionUrl object is created in a different stack and passed in to the cloudformation stack, the definition looks like:

    this.functionUrl = new FunctionUrl(this, 'LambdaApiUrl', {
      function: this.lambdaFunction,
      authType: FunctionUrlAuthType.NONE,
      cors: {
        allowedOrigins: ["*"],
        allowedMethods: [HttpMethod.GET, HttpMethod.POST],
        allowCredentials: true,
        maxAge: Duration.minutes(1)
      }
    });

The above code fails because "The parameter origin name cannot contain a colon". Presumably, this is because functionUrl.url evaluates to something like https://xxx.lambda-url.ap-southeast-2.on.aws/ (note the https:// ) whereas the HttpOrigin parameter should just be the domain name like xxx.lambda-url.ap-southeast-2.on.aws .

I can't just write code to hack the url up though (ie functionUrl.url.replace("https://", "") ) because when my code executes, the value or the url property is a token like ${Token[TOKEN.350]} .

The function url is working properly: if I hard-code the HttpOrigin to the function url's value (ie like xxx.lambda-url.ap-southeast-2.on.aws ) - it works fine.

How do I use CDK code to setup the reference from Cloudfront to the function url?

I'm using aws-cdk version 2.21.1.

---

There is an open issue to add support: https://github.com/aws/aws-cdk/issues/20090

Answer 1

UseCloudFormation Intrinsic Functions to parse the url string:

cdk.Fn.select(2, cdk.Fn.split('/', functionUrl.url));

// -> 7w3ryzihloepxxxxxxxapzpagi0ojzwo.lambda-url.us-east-1.on.aws