[cloudfront] Cache Policies for CloudFrontWebDistribution

Support for Cache Policies was released for the Distribution construct in #10656. This feature request tracks porting that same support over to the CloudFrontWebDistribution construct.

Use Case

For users of the stable CloudFrontWebDistribution construct who want to be able to control the cache key and TTLs.

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This is a 🚀 Feature Request

[nwitte-rocketloans]

I switched to this construct because the Distribution construct doesn’t have custom origin headers, but now I don’t have automation for setting cache policy.

[robertd]

The Distribution construct seems to be missing the ability to use custom headers on S3 Origins, which was why I switched to CloudfrontWebDistribution. I seem to be in an endless loop here because there are 3 Cloudfront Distribution constructs and all of them seem to be misssing features that I need. CfnDistribution doesn’t have a clear answer to associating Lambda@Edge functions to Cloudfront events.

CfnDistribution is an L1 construct where as CloudfrontWebDistribution and Distribution are L2 (opinionated) constructs. Typically, Cfn* constructs are used as a last resort.

Here is an example attaching lambda@edge function to a CF distro. Note that this is an experimental functionality. However, we’re using it in prod and so far it’s been really good. Also, CloudFront functions are a new thing (https://aws.amazon.com/blogs/aws/introducing-cloudfront-functions-run-your-code-at-the-edge-with-low-latency-at-any-scale/)… it’s worth taking a peek at those if you haven’t already.

const edgeLambda = new cloudfront.experimental.EdgeFunction(this, 'lambda-edge', {
  runtime: lambda.Runtime.NODEJS_14_X,
  handler: 'index.handler',
  code: lambda.Code.fromAsset(path.join(__dirname, 'path/to/function')),
});

const distro = new cloudfront.Distribution(this, 'distro', {
  defaultBehavior: {
    ...
    edgeLambdas: {
      functionVersion: edgeLambda.currentVersion,
      eventType: cloudfront.LambdaEdgeEventType.ORIGIN_REQUEST, // see https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/lambda-cloudfront-trigger-events.html
    },
    ...
  },
...
});

I’ll have to test custom headers on S3 origins for a bit… but I bet you can use escape hatches to apply those if they’re not officially supported yet. (https://docs.aws.amazon.com/cdk/latest/guide/cfn_layer.html)