daemon.rb

require "English"
require "logger"
require "pathname"

# kill me with kill -INT PID

script_path = Pathname(__FILE__)
pid_file = script_path.sub_ext(".pid")
pid_file.write(String(Process.pid))

log_file = Pathname(script_path).sub_ext(".log")
logger = Logger.new(log_file, 7, 1024*1024)
logger.level = Logger::DEBUG
logger.debug "PID: #{Process.pid}"

shutdown = false
on_int_or_term_signal = proc {
                          p "Received shutdown signal"
                          # signal handler may have already deleted the PIDFILE
                          pid_file.unlink if pid_file.exist?
                          if $ERROR_INFO
                            p "#{$ERROR_INFO} - POS: #{$ERROR_POSITION}"
                          end
                          shutdown = true
                        }
trap("INT", &on_int_or_term_signal)
# trap("TERM", &on_int_or_term_signal)
# at_exit(&on_int_or_term_signal)

workers = 1.upto(4).map { |i|
  Thread.new(i) do |j|
    loop do
      break if shutdown

      logger.debug "Thread ##{j} about to go to sleep"
      sleep(j)
    end
  end
}

loop do
  sleep 1

  if shutdown
    workers.each.with_index do |worker, i|
      res = begin
              worker.join(i + 1)
            rescue => err
              logger.error err.message
              logger.error err.backtrace.join("\n")
              true # thread already killed
            end

      Thread.kill(worker) unless res
    end

    break
  end
end