Cyclic redirect with CloudFront

[mister]

Hello,

The Lambda function is working well, but I have cyclic redirect when trying to configure it with CloudFront.

I created a CloudFront distribution with default settings and used S3's static website endpoint as the origin. Also, I used the CloudFront domain name for the URL Lambda envonment variable.

Existing images are served well. But for new images I receive redirects loop between API gateway and CloudFront. What is interesting, new image generated and accessible with S3's endpoint. Can't get what is wrong.

Any ideas on how to fix it?
Thank you.

[sagidM]

Thank you for issuing.
Unfortunately, I have not experienced CloudFront yet, but from what you have explained, the issue seems to be either on the CloudFront hand or in incorrectness of parameters.

If success, the lambda redirects to {URL}/{path}.

I would check the full url.
In your case, request to the full url redirects back to the lambda which causes a cycle.

You mentioned, a new image is generated and accessible.
Well, if you can open the generated image in your browser, then just make sure you are requesting the lambda with an appropriate path.

If this does not help, please let me know.
Also, specific examples might have clarified the case, e. g. the addresses of your lambda and CloudFront server (you may create temporary ones).

[mister]

Hi @sagidM,

Lambda does redirect to the correct path, as you mentioned. For example, when a user visits
https://abcdefg.cloudfront.net/250xAUTO/f350fd70-b516-11e9-b57d-01a3c7a72c2d.jpg he will be redirected to API endpoint with 307 status, eg. https://myapi123.execute-api.us-east-1.amazonaws.com/prod. Once Lambda finished, the user redirected back to the initial URL with a 301 status code. At this point, a new image created and exists. But browser redirects back to API endpoint again.

What is interesting, the image becomes available through S3 website endpoint, but not through CDN. As far I understood after digging deeper, the issue related to CloudFront cache. It caches redirects. So, after the first redirect to API endpoint, CF caches destination URL and status code and does same action one next visit. On this case - when Lambda returns redirect path.

[sagidM]

If you request https://abcdefg.cloudfront.net/250xAUTO/f350fd70-b516-11e9-b57d-01a3c7a72c2d.jpg again in your browser, can you see the image?
If not, can you see it via a hard reload Ctrl+Shift+R?

[mister]

No, browser redirects to API gateway again. The problem in CloudFront cache behavior (
https://docs.aws.amazon.com/en_us/AmazonCloudFront/latest/DeveloperGuide/http-3xx-status-codes.html)

Fixed by setting up CloudFlare distribution Cache Default TTL to 0 and added CacheControl to images created by Lambda:

...
.then(result =>
    S3.putObject({
        Body: result,
        Bucket: BUCKET,
        ContentType: contentType,
        Key: path,
        CacheControl: 'public, max-age=86400'
    }).promise()
)
...

[sagidM]

Cool, thank you for sharing.
Hope this helps others