Ruby program in multiple threads (proof of concept)

executer.rb

# List of IDs of entities to be processed
ids = ("a".."z").to_a
# Break in groups of 5 (or any other number) 
groups = ids.each_slice(5)

# Make sure that exceptions will spread.
# By default the are silenced within threads
# so you want know why your program crashed.
Thread.abort_on_exception = true

threads = []

groups.each_with_index do |group, index|
  ids_to_process = group.join(",")
  threads << Thread.new do
    system "ruby main.rb #{ids_to_process} > log-group-#{index}.txt"
    puts "Started process for group #{index}"
    puts "Inspect logs by running tail -f log-group-#{index}.txt"
  end
end

threads.each(&:join)

main.rb

ids_to_process = ARGV[0].split(",")

ids_to_process.each do |id|
  puts "************************"
  puts "Processing #{id}"
  # Just to make it randomly slow and have time to see the logs
  (1_000_000..10_000_000).to_a.sample.times { print "." }
  puts "******** END ***********"
end