AWS Lambda examples

Reconstruct CloudFront URLs

exports.handler = (event, context, callback) => {
  // Extract the request from the CloudFront event that is sent to Lambda@Edge
  var request = event.Records[0].cf.request;

  // Extract the URI from the request
  var olduri = request.uri;

  // Match any '/' that occurs at the end of a URI. Replace it with a default index
  var newuri = olduri.replace(/\/$/, "/index.html");

  // Replace the received URI with the URI that includes the index page
  request.uri = newuri;

  // Return to CloudFront
  return callback(null, request);
};

Let’s walk through the above example making reference to the general structure of the AWS Lambda handler function:

  1. The event parameter is invoked to gain access to the event that triggered the function. This is a CloudFront request event which is targetted with event.Records[0].cf.request
  2. We classify this request as the olduri since it doesn’t have the form we want.
  3. We mutate the original request by replacing / with /index.html
  4. We then re-assign the request.uri value to the value of the new URI.
  5. Finally we invoke the callback parameter to signal the completion of the transformation and return the new request as the return value.
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