Origin request lambda causes nothing to be returned from origin

Question

I have a cloudfront distribution with s3 as my origin. The bucket contains only an index.html file.

The cloudfront distribution has an origin policy to forward Cloudfront-Viewer-Country, Accept-Language, and all cookies from the viewer request.

With the aforementioned I am able to visit my test url without any problems. Everything loads fine.

When I create an origin request lambda@edge function that simply reads the CloudFront-Viewer-Country value and stores that in a cookie like so:

'use strict';

/* This is an origin request function */
exports.handler = (event, context, callback) => {
  const request = event.Records[0].cf.request;
  const headers = request.headers;
  const countryCode = headers['cloudfront-viewer-country'] ? headers['cloudfront-viewer-country'][0].value : 'CA'; 

  const response = {
    status: '200',
    headers: {
        'set-cookie': [{
            key: 'set-cookie',
            value: 'locale='+countryCode,
        }]
    },
  };
  callback(null, response);
};

Then I deploy the lambda, setup the cloudfront trigger, invalidate the cache and then try to navigate to my test url nothing is returned. The screen is just blank :(

Is there something wrong with my lambda function? If I disassociate the lambda origin request function from the cloudfront distribution then invalidate the cache, everything works again.

Answer 1

The edge lambda is supposed to modify the request/response object and return it, not replace it with a new object with the rest of the properties absent.

Something like this:

exports.handler = (event, context, callback) => {
  const request = event.Records[0].cf.request;
  const headers = request.headers;
  const countryCode = headers['cloudfront-viewer-country'] ? headers['cloudfront-viewer-country'][0].value : 'CA'; 

  headers['set-cookie'] = [
    [{
      key: 'set-cookie',
      value: 'locale='+countryCode,
    }]
  ];

  callback(null, request);
};