daemon.rb

module Minion
  module Daemon
    extend self
    attr_accessor :pid, :log
    
    def fork_or_skip
      
      arg = ARGV.join(" ")[/\-d\s\d+/] || ARGV.join(" ")[/\-d/]
      
      return unless arg
      workers = (arg[/\d+/] || 1).to_i
      
      ensure_dirs
      
      workers.times do |process_num|
        if child_pid = fork() # parent process
          p [process_num, workers]
          next if process_num < workers - 1
          exit if process_num == workers - 1
        end
        
        puts "started #{process_num} #{Process.pid()}"
        Process.setsid()
        
        try_kill_previous(process_num)  unless pid
        write_pid(process_num)          unless pid
        
        write_logs(process_num)
      end
      
    end
    
    def pid_folder
      File.basedir(pid)
    end
    
    def log_folder
      File.basedir(log)
    end
    
    def ensure_dirs
      `mkdir -p #{pid_folder}` if pid
      `mkdir -p #{log_folder}` if log
    end
    
    def file_for(method, number)
      send(method) + ".#{number}"
    end
    
    def write_pid(number)
      return 
      File.open(file_for(:pid, number), 'w') {|file| file.write(Process.pid())}
    end
    
    def write_logs(number)
      #$stdin.close()
      if log
        $stdout.reopen(file_for(:pid, number) + '.log', "w")
        $stderr.reopen(file_for(:pid, number) + '.err', "w")
      else
        #$stdout.reopen('/dev/null', "w")
        #$stderr.reopen('/dev/null', "w")
      end
      
    end
    
    def try_kill_previous(number)
      return unless pid
      pidfile = file_for(:pid, number)
      
      if File.exist?(pidfile)
        pid_to_kill = File.open(pidfile) {|f| f.read }
        
        Process.kill("HUP", pid_to_kill)
        Process.wait
      end
    end
    
  end
end