daemons_race.rb

#!/usr/bin/env ruby

require "daemons"
require "fileutils"

module Daemons
  class Controller

    def catch_exceptions(&block)
      begin
        block.call
        @error = false
      rescue CmdException, OptionParser::ParseError => e
        @error = true
        puts "ERROR: #{e.to_s}"
        puts
        print_usage()
      rescue RuntimeException => e
        @error = true
        puts "ERROR: #{e.to_s}"
      end
    end

    def error?
      @error == true
    end

  end
end

class DaemonStarter

  def initialize(name)
    @filename = File.expand_path(name + ".starting")
    @pid = File.expand_path(name = ".pid")
  end

  # Check if the daemon should start
  def start?
    if not(ARGV.include? "start" or ARGV.include? "restart") then
      # some command other than start or restart
      return true
    end

    return false if File.exists? @filename

    FileUtils.touch(@filename)
    @file = File.new(@filename)
    if @file.flock(File::LOCK_EX|File::LOCK_NB) == false then
      return false
    end

    return true
  end

  def cleanup!
    puts "cleanup: #{File.exists? @pid}"
    begin
      @file.flock(File::LOCK_UN) # unlock
    rescue => ex
    end
    begin
      File.delete(@filename) if File.exists? @filename
    rescue => ex
    end
  end

end

starter = DaemonStarter.new(File.expand_path("race"))
exit if not starter.start?

Daemons.run_proc('race', :log_output => true, :dir => Dir.pwd, :dir_mode => :normal) do
  starter.cleanup!
  loop do
    puts "hello from process #{Process.pid}"
    sleep 5
  end
end

starter.cleanup! if Daemons.controller.error?