Thread safe

time_zone_test.rb

worker_num = 10
workers = []

(1..worker_num).each do |i|
  workers << Thread.new do
    loop {
      sleep rand(10)
      puts "worker[#{i}]: #{Time.zone}"
      Time.zone = "Asia/Tokyo" if i == 1
    }
  end
end

workers.each {|w| w.join}