tar_streamer.rb

map "/tar" do
  use RailsEnvConfigMiddleware
  use Rack::Auth::Basic, "Private data" do |username, password|
    User.auth(username,password)
  end
  run StreamTar
end
StreamTar = ->(env) {
  hijack_proc = ->(socket) {
    IO.popen("tar --to-stdout -c #{env['tar_path']}", external_encoding: Encoding::BINARY) do |tar_io|
      loop do
        break if tar_io.eof?
        tar_chunk = tar_io.read(64*1024)
        socket.write(tar_chunk) if tar_chunk
      end
    end
    socket.close unless socket.closed?
  }
  return [200, {
    'Content-Disposition'=>"attachment;filename=#{env['filename']}",
    'Content-Type'=>'application/octet-stream',
    'Connection'=>'keep-alive',
    'Content-Transfer-Encoding'=>'binary',
    'rack.hijack' => hijack_proc
  }, []]
}