forker.rb

# @usage Start and stop a ruby process that just logs to a file every couple seconds, but can be interrupted gracefully
#
#   ruby script/wb
#   kill -INT `cat tmp/pids/wb.pid`
#
require "logger"
require "fileutils"
PID_FILE = File.expand_path("../../tmp/pids/wb.pid", __FILE__)
LOG_FILE = File.expand_path("../../log/wb.log", __FILE__)

module Worker
  extend self

  def call
    logger.info "Hello world"
    Thread.new do
      loop do
        logger.info %w[Howdy Hi Hey Yo Hohoho].sample << ", just checkin in"
        sleep 2
        if stop?
          logger.info "Stopping ..."
          break
        end
      end
    end
  end

  def fork
    Kernel.fork do
      trap("INT") do
        begin
          puts "Shutting down ..."
          Worker.stop
          FileUtils.rm(LOG_FILE)
          FileUtils.rm(PID_FILE)
        rescue Errno::ENOENT
          puts "Nothing to cleanup, log PID_FILE not found"
        end
        raise SignalException.new('INT') unless ENV["NORAISE"]
      end
      yield if block_given?
    end
  end

  def stop
    @exit = true
  end

  def stop?
    !!@exit
  end

  def logger
    @logger ||= Logger.new LOG_FILE
  end
end

puts "Starting", "Monitor the process with:", "", " tail -f log/wb.log", ""
child = Worker.fork { Worker.call.join }
if ARGV.include?("-d")
  puts "Daemonizing ..."
  puts "Dumping PID #{child} to '#{PID_FILE}'"
  File.open(PID_FILE, 'wb') { |f| f.puts(child) }
  puts "Stop with: kill -INT `cat tmp/pids/wb.pid`"
  puts "Done."
else
  puts "Pass the -d option to daemonize. Press Ctrl-C to quit..."
  Process.wait child
end