class Puma::Server

def graceful_shutdown
  if @options[:shutdown_debug]
    threads = Thread.list
    total = threads.size
    pid = Process.pid
    $stdout.syswrite "#{pid}: === Begin thread backtrace dump ===\n"
    threads.each_with_index do |t,i|
      $stdout.syswrite "#{pid}: Thread #{i+1}/#{total}: #{t.inspect}\n"
      $stdout.syswrite "#{pid}: #{t.backtrace.join("\n#{pid}: ")}\n\n"
    end
    $stdout.syswrite "#{pid}: === End thread backtrace dump ===\n"
  end
  if @options[:drain_on_shutdown]
    count = 0
    while true
      ios = IO.select @binder.ios, nil, nil, 0
      break unless ios
      ios.first.each do |sock|
        begin
          if io = sock.accept_nonblock
            count += 1
            client = Client.new io, @binder.env(sock)
            @thread_pool << client
          end
        rescue SystemCallError
        end
      end
    end
    @events.debug "Drained #{count} additional connections."
  end
  if @status != :restart
    @binder.close
  end
  if @thread_pool
    if timeout = @options[:force_shutdown_after]
      @thread_pool.shutdown timeout.to_i
    else
      @thread_pool.shutdown
    end
  end
end