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amazon-web-servicesamazon-cloudfront

AWS Edge function for dynamic routing not working

I'm having trouble setting up an easy example using Cloudfront@Edge functions for changing the custom origin of a request, while keeping the domain name.

Following this guide and this stackoverflow question I have the following setup:

  • 2 HTTP Load Balancers, each with a lambda function. They return an HTTP page with the Region + all the headers in the body:
    • 1 in US: custom-us.us-west-1.elb.amazonaws.com
    • 1 in EU: custom-eu.eu-central-1.elb.amazonaws.com
  • 1 cloudfront distribution (mydistr.cloudfront.net) with 1 origin, as done in the guide. My origin for the default behavior is custom-us.us-west-1.elb.amazonaws.com. The cache policy is Managed-CachingDisabled.
  • 1 cloudfront@edge lambda function (with origin-request trigger) with the following code:
'use strict';

module.exports.dynamic_routing = (event, context, callback) => {
  const request = event.Records[0].cf.request;  
  const originUSA = "custom-us.us-west-1.elb.amazonaws.com";
  const originEU = "custom-eu.eu-central-1.elb.amazonaws.com";

  var destDomain = originUSA;
 
  const custom_header = request.headers['custom-header-value'];
  if (custom_header && custom_header.value == "DE") {
      destDomain = originEU;
  }
  
  request.origin = {
      custom: {
          domainName: destDomain,
          port: 80,
          protocol: 'http',
          path: request.uri,
          readTimeout: 20,
          keepaliveTimeout: 5,
          customHeaders: {}
      }
  };
  request.headers['host'] = [{ key: 'host', value: destDomain}];
  
  callback(null, request);
};

I can correctly navigate to both Load Balancers and see the right content, which proves that the load balancers + respective lambda functions are correctly setup.

If I navigate to mydistr.cloudfront.net the "USA" content is shown, which is correct. However, if send a request with Curl/Postman including my custom-header-value: DE, I keep seeing the USA info: enter image description here

when I expected to have changed the origin.

What am I missing?

Solution

  • Well...the solution was quite simple.

    All the headers are arrays and thus the problem was here: custom_header.value == "DE" where it should in fact be custom_header[0].value == "DE".