A ruby script that, upon interrupt, delays exit until after a method has completed execution

at_exit_uninterruptable.rb

def operation(iteration)
  # ... As implemented above
end


# Only runs if the file is the entry point for execution,
# but not if loaded as a library
if $0 == __FILE__
  puts "[INFO #{Time.now}] #--- Starting Worker Program ---#"
  
  thread = nil

  # This  block only runs when the program is about to exit. It waits for
  # the running thread to complete before continuing with the exit operation
  at_exit do
    puts "[WARN #{Time.now}] #--- INTERRUPT RECEIVED ---#"
    puts "[WARN #{Time.now}] Waiting for current iteration to complete. " \
      "Interrupt again for immediate (unsafe) termination."

    # Wait for the currently running thread to exit before continuing execution
    thread.join

    puts "[INFO #{Time.now}] #--- ITERATION COMPLETED. EXITING " \
      "SAFELY ---#"
  end

  iteration = 0

  # Main loop
  while true
    thread = Thread.new{ operation(iteration) }

    # Wait for thread to complete before proceeding. Otherwise, this while
    # loop would quickly spin up the maximum number of threads all running
    # concurrently.
    thread.join
    iteration += 1
  end
end