Save image versions with Refile with streaming as a fallback

aws_uploader.rb

class AwsUploader
	CLIENT = Aws::S3::Client.new
	BUCKET = Rails.configuration.x.aws["output_bucket"]

	def self.upload(file, key)
		CLIENT.put_object({
			bucket: BUCKET,
			key: key,
			body: file,
			content_length: file.size
		})
	end

	def self.delete(key)
		resp = CLIENT.list_objects({
			bucket: BUCKET,
			prefix: key
		})

		CLIENT.delete_objects({
			bucket: BUCKET,
			delete: {
				objects: resp.contents.map{|c| c.to_hash.slice(:key)}
			}
		})
	end
end

cache_thumbnails_job.rb

class CacheThumbnailsJob < ActiveJob::Base
	queue_as :default

	def perform(post)
		versions = {}
		extension = post.thumbnail_attacher.extension
		source_file = Refile.store.get(post.thumbnail_id).download

		Post.thumbnails.each do |k, attrs|
			filename = "#{k}.#{extension}"
			key = [post.thumbnail_prefix, filename].join("/")
			file = Refile.processors[attrs[:processor]].call(source_file, attrs[:width], attrs[:height])

			AwsUploader.upload(file, key)
			versions[k] = filename
		end

		# thumbnail_versions is an hstore column
		post.update(thumbnail_versions: versions)
	end
end

delete_thumbnail_job.rb

class DeleteThumbnailsJob < ActiveJob::Base
	queue_as :default

	def perform(key)
		AwsUploader.delete(key)
	end
end

post.rb

class Post < ActiveRecord::Base
	attachment :thumbnail, type: :image

	def self.thumbnails
		@thumbnails ||= {
			md: {
				processor: "fill",
				width: 480,
				height: 270
			},
			md2x: {
				processor: "fill",
				width: 960,
				height: 540
			}
		}
	end
	
	after_save :cache_thumbnails
	
	def thumbnail_prefix(key=nil)
		['thumbnails', (key || thumbnail_id)].join('/')
	end
	
private

	def cache_thumbnails
		if thumbnail_id_changed?
			CacheThumbnailsJob.perform_later(self) if thumbnail_id.present?
			DeleteThumbnailsJob.perform_later(thumbnail_prefix(thumbnail_id_was)) if thumbnail_id_was.present?
		end
	end
end

posts_helper.rb

module PostsHelper
	def thumbnail_url(post, version)
		filename = post.thumbnail_versions[version.to_s]

		if filename.present?
			[Rails.configuration.x.cdn_host, post.thumbnail_prefix, filename].join('/')
		else
			# Fallback to Refile URL if not generated yet
			specs = Post.thumbnails[version]
			attachment_url(post, :thumbnail, specs[:processor], specs[:width], specs[:height])
		end
	end
end

This looks nice. I will try to adopt it.

But I don't want the jobs to run. I'd rather delete all thumbnails after let's say 30 days and the call to a thumbnail checks if it exists and if not generates it. I don't know if this is possible. What do you think?

You could have a cron job that runs a Rake task which uses the AWS SDK to check if an object exists, and if not generate some thumbnails. In regards to deleting old thumbnails, you'd either need to keep track of the old image hashes/filenames or run some sort of diff on what's in your local database vs. what's listed in S3 and delete anything in S3 that isn't stored locally (which sounds kinda clunky).