How to add a custom service to ActiveStorage

Question

I want to add a custom service to ActiveStorage because I want to overwrite the url method of the ActiveStorage::Service::S3Service service so I can use a CloudFront CDN in front of my S3 bucket. I think I will not need the presigned_url params, I will just need the key, because the CloudFront instance will have full read access to the S3 bucket.

Answer 1

Add a class in the ActiveStorage::Service namespace that subclasses ActiveStorage::Service::S3Service. Override the methods you want to override. For example:

# lib/active_storage/service/cloudfront_s3_service.rb 
require "active_storage/service/s3_service"

class ActiveStorage::Service::CloudfrontS3Service < ActiveStorage::Service::S3Service
  def url(key, **)
    # ...
  end
end

Refer to your custom service in config/storage.yml:

production:
  service: CloudfrontS3
  access_key_id: ""
  secret_access_key: ""
  region: ""
  bucket: ""