Invalidate CloudFront cache of S3 assets in Comfortable Mexican Sofa after update or destroy using the Fog gem

application.rb

module YourApp
  class Application < Rails::Application
    config.after_initialize do
      Comfy::Cms::File.send(:include, ComfyCloudfront)
    end
  end
end

require 'comfy_cloudfront'

comfy_cloudfront.rb

module ComfyCloudfront
  def self.included(base)
    base.after_validation :invalidate_cloudfront, on: :update
  end

  def destroy
    super if invalidate_cloudfront
  end

  def invalidate_cloudfront
    begin
      cdn = Fog::CDN.new({
        provider:              'AWS',
        aws_access_key_id:     ENV['AWS_ACCESS_KEY_ID'],
        aws_secret_access_key: ENV['AWS_SECRET_ACCESS_KEY']
      })

      cdn.post_invalidation(ENV['CLOUDFRONT_DISTRIBUTION_ID'], ["/#{file.path}", "/#{file.path(:cms_thumb)}"])

    rescue Excon::Errors::BadRequest
      return false
    end
  end
end