Upload assets to S3, preserve two most recent versions.

assets.rake

namespace :assets do

  # uploads assets to s3 under assets/githash, deletes stale assets
  task :uploadToS3, [ :to ] => :environment do |t, args|
    from = File.join(Rails.root, 'public/assets')
    to = args[:to]
    hash = (`git rev-parse --short HEAD` || "").chomp
    
    logger.info("[#{Time.now}] fetching keys from #{to}")
    existing_objects_hash = {}
    existing_assets_hash = {}
    s3i.incrementally_list_bucket(to, prefix: "assets/") do |response|
      response[:contents].each do |existing_object|
        existing_objects_hash[existing_object[:key]] = existing_object
        previous_asset_hash = existing_object[:key].split('/')[1]
        existing_assets_hash[previous_asset_hash] ||= DateTime.parse(existing_object[:last_modified]) 
      end
    end

    logger.info("[#{Time.now}] #{existing_assets_hash.count} existing asset(s)")
    previous_hash = nil
    existing_assets_hash.each_pair do |asset_hash, last_modified|
      logger.info(" #{asset_hash} => #{last_modified}")
      previous_hash = asset_hash unless (previous_hash and existing_assets_hash[previous_hash] > last_modified)
    end
    logger.info("[#{Time.now}] keeping #{previous_hash}") if previous_hash
  
    logger.info("[#{Time.now}] copying from #{from} to s3:#{to} @ #{hash}")
    Dir.glob(from + "/**/*").each do |entry|
      next if File::directory?(entry)
      File.open(entry) do |entry_file|
        content_options = {}
        content_type = MIME::Types.type_for(entry)[0]
        content_options['x-amz-acl'] = 'public-read'
        if entry.ends_with?('.gz')
          uncompressed_entry = entry[0..-4]
          entry = "#{uncompressed_entry}.cgz"
          content_type = MIME::Types.type_for(uncompressed_entry)[0]
          content_options['content-encoding'] = 'gzip'
        end
        content_options['content-type'] = content_type.to_s
        key = 'assets/'
        key += (hash + '/') if hash
        key += entry.slice(from.length + 1, entry.length - from.length - 1)
        existing_objects_hash.delete(key)
        logger.info("[#{Time.now}]  uploading #{key} (#{content_type})")
        s3i.put(to, key, entry_file, content_options)
      end
    end
    
    existing_objects_hash.keys.each do |key|
      next if previous_hash and key.start_with?("assets/#{previous_hash}/")
      puts "deleting #{key}"
      s3i.delete(to, key)
    end
  end
      
  namespace :push do
    task :to_staging => [ :environment, :assets ] do
      Rake::Task["assets:uploadToS3"].execute({ to: 'staging-bucket' })
    end
    task :to_production => [ :environment, :assets ] do
      Rake::Task["assets:uploadToS3"].execute({ to: 'production-bucket' })
    end
    task :to_heroku => [ :environment, :assets ] do
      s3_bucket = Heroku::Config['S3_BUCKET']
      raise "missing S3_BUCKET in heroku config" if (s3_bucket.nil?)
      Rake::Task["assets:uploadToS3"].execute({ to: s3_bucket })
    end
  end
  
end