Lambda@Edge Cache-Control header not present Cloudfront

Question

I've images stored on S3 and a lambda function to resize them on the fly. While doing it I add CacheControl: 'max-age=31536000' to the resized images and also add a Cache-Control header:

.then(buffer => {
  // save the resized object to S3 bucket with appropriate object key.
  S3.putObject({
    Body: buffer,
    Bucket: BUCKET,
    ContentType: 'image/jpg',
    CacheControl: 'max-age=31536000',
    Key: `uploads/${key}`,
  })

  // generate a binary response with resized image
  response.status = 200
  response.body = buffer.toString('base64')
  response.bodyEncoding = 'base64'
  response.headers['content-type'] = [{ key: 'Content-Type', value: 'image/jpg' }]
  response.headers['cache-control'] = [{ key: 'Cache-Control', value: 'public, max-age=31536000' }]
  callback(null, response)
})

And if the thumbnail has already been generated, I just do:

if (!response.headers['cache-control']) {
  response.headers['cache-control'] = [{ key: 'Cache-Control', value: 'public, max-age=31536000' }]
}
callback(null, response)

On my Cloudfront distribution, I've the following settings:

• Cache Based on Selected Request Headers: None
• Object Caching: Use Origin Cache Headers

The lambda works fine but when I look in the devtools, it seems that Chrome never cache the images. Here is the info I get:

General
  Request URL: https://aws.mydomain.com/478/dd123cd5-1636-47d0-b756-e6c6e9cb28c0/normal/pic.jpg
  Request Method: GET
  Status Code: 200 
  Remote Address: 52.84.31.149:443
  Referrer Policy: no-referrer-when-downgrade
  age: 382

Response Headers
  content-length: 49192
  content-type: image/jpg
  date: Thu, 09 May 2019 20:41:42 GMT
  server: AmazonS3
  status: 200
  via: 1.1 261e801dca9c54ff576f39f96d80ede5.cloudfront.net (CloudFront)
  x-amz-cf-id: ZlheiBoNDuYDeuvZo0jBP6Zjpge5AonPGlCo_N2pHhHdGwV7DorKtA==
  x-amz-id-2: xkDxIB0qDJt5KMeHINq7/gaRII6EDBOsL3SlMuhMwJ84M/lak9E/tcRChv7vvYurD+2hYOT8kSI=
  x-amz-request-id: CAD9AE1E905BB13A
  x-cache: Hit from cloudfront

Request Headers
  :authority: aws.mydomain.com
  :method: GET
  :path: /478/dd123cd5-1636-47d0-b756-e6c6e9cb28c0/normal/pic.jpg
  :scheme: https
  accept: */*
  accept-encoding: gzip, deflate, br
  accept-language: en-US,en;q=0.9
  user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.108 Safari/537.36

Control-Cache is not present and I can't figure this out...

When I invalidate all the images in the distribution, the only change is the value of x-cache: 'Error from cloudfront' on the first load (status 200 and image is loaded ok)

Answer 1

Ok, so apparently it's not possible to add cache-control headers in an origin-response lambda. You have to do it in a viewer-response lambda. Something like that:

exports.handler = (event, context, callback) => {
  const response = event.Records[0].cf.response;
  if (!response.headers['cache-control']) {
    response.headers['cache-control'] = [{
      key: 'Cache-Control',
      value: 'max-age=31536000'
    }];
  }
  callback(null, response);
};