signal_trap_uninterruptable.rb

def operation(iteration)
  # ... As implementd 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
  iteration = 0

  begin
    # 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

  # 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
  rescue SignalException => e
    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
end