naiv-non-blocking.rb

def process_partial_file_input(data)
  # Do something cool with data
end

# Event loop

big_file = "network/path/big_file.xlsx"
file_handler = open(big_file)
files_to_look_after = [file_handler]

loop do
  puts "(Re)Starting the Event loop"
  # 1. Step: Check if IO event is ready from the  OS. Wait
  # for 10 ms to be notified 
  # A more advanced event loop wouldn't use select since this is
  # activly asking the os but would use something like epoll.
  # But this is not available in Ruby so we fallback to this
  # method
  readable, _writeable = IO.select files_to_look_after, [], [], 0.01

  # 2. Step: Handle readable connection
  if readable
    readable.each do |ready_io|
      # We will read 4096 bytes in each iteration
      read_data = ready_io.read_nonblock(4096)

      # 3. Step: Process data according to business logic
      process_partial_file_input read_data if read_data
    rescue EOFError => e
      files_to_look_after.reject! {|file| file == ready_io }
    end
  end


  break if files_to_look_after.empty?
end