CODEWITHSUNDEEP
amazon-s3
brenjt
brenjt

Reputation: 16297

S3 Fallback Bucket

I have built a system where I have product templates. A brand will overwrite the template to create a product. Images can be uploaded to the template and be overwritten on the product. The product images are uploaded to the corresponding brand's S3 bucket. But on the product template images are uploaded to a generic S3 bucket.

Is there a way to make the brand's bucket fallback to the generic bucket if it receives a 404 or 403 with a file url. Similar to the hosted website redirect rules? These are just buckets with images so it wouldn't be a hosted website and I was hoping to avoid turning that on.

Upvotes: 0

Views: 831

Answers (1)

Michael - sqlbot
Michael - sqlbot

Reputation: 179054

There is not a way to do this with S3 alone, but it can be done with CloudFront, in conjunction with two S3 buckets, configured in an origin group with appropriate origin failover settings, so that 403/404 errors from the first bucket cause CloudFront to make a follow-up request from the second bucket.

After you configure origin failover for a cache behavior, CloudFront does the following for viewer requests:

  • When there’s a cache hit, CloudFront returns the requested file.

  • When there’s a cache miss, CloudFront routes the request to the primary origin that you identified in the origin group.

  • When a status code that has not been configured for failover is returned, such as an HTTP 2xx or HTTP 3xx status code, CloudFront serves the requested content.

  • When the primary origin returns an HTTP status code that you’ve configured for failover, or after a timeout, CloudFront routes the request to the backup origin in the origin group.

https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/high_availability_origin_failover.html

This seems to be the desired behavior you're describing. It means, of course, that cache misses that need to fall back to the second bucket will require additional time to be served, but for cache hits, there won't be any delay since CloudFront only goes through the "try one, then try the other" on cache misses. It also means that you'll be paying for some traffic on the primary bucket for objects that aren't present, so it makes the most sense sense if the primary bucket will have the object more often than not.

This solution does not redirect the browser -- CloudFront follows the second path before returning a response -- so you'll want to be mindful of the Cache-Control settings you attach to the fallback objects when you upload them, since adding a (previously-absent) primary object after a fallback object is already fetched and cached (by either CloudFront or the browser) will not be visible until any cached objects expire.

Upvotes: 2

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