Migrate Paperclip assets from filesystem to AWS S3

migrate_s3.rake

namespace :attachments do
  task migrate_to_s3: :environment do
    require 'aws-sdk'

    # Define Paperclip models
    models = [
      [Attachment, :data],
      [Image, :data],
      [MediaAppearance, :media_logo],
      [Testimonial, :avatar_logo]
    ]

    # Load credentials and config
    s3_options        = YAML.load_file(File.join(Rails.root, 'config/aws.yml'))[Rails.env].symbolize_keys
    paperclip_options = YAML.load_file(File.join(Rails.root, 'config/paperclip.yml'))[Rails.env].symbolize_keys
    bucket_name       = paperclip_options[:bucket]

    # Establish S3 connection
    AWS.config(s3_options)
    s3      = AWS::S3.new
    bucket  = s3.buckets[bucket_name]

    models.each do |klass, field|
      styles  = []

      klass.first.send(field).styles.each do |style|
        styles.push(style[0])
      end
      styles.push(:original)

      # Process
      klass.find_each.with_index do |attachment, n|
        styles.each do |style|
          path = attachment.send(field).path(style)
          next if path.nil?

          begin
            bucket.objects[path.sub!(%r{^/}, '')].write(file: File.join(Rails.public_path, path))
            puts "-> Saved #{path} to S3 (#{n}/#{klass.count})"
          rescue AWS::S3::Errors::NoSuchBucket => e
            puts "--- Creating bucket named: #{bucket_name} ---"
            AWS::S3.new.buckets.create(bucket_name)
            retry
          rescue StandardError => e
            puts "Error on (#{n}/#{klass.count}): #{e}"
          end
        end
      end
    end
  end
end