An attempt to daemonize JRuby scripts with Spoon gem.

README.md

Usage:

SpoonDaemon.new('start', 'path/to/my/script.rb', 'tmp/pids')

spoon_daemon.rb

require 'spoon'

class SpoonDaemon
  def initialize(cmd, script, pid_dir)
    @script = script
    @pid_dir = pid_dir
    @pid_path = File.join(@pid_dir, "#{File.basename(script)}.pid")

    case cmd
    when 'start'
      start
    when 'stop'
      stop
    when 'restart'
      stop
      start
    else
      STDERR.puts "Usage: <script> <start|stop|restart>"
      exit!
    end
  end

  def create_pid(pid)
    begin
      open(@pid_path, 'w') do |f|
        f.puts pid
      end
    rescue => e
      STDERR.puts "Error: Unable to open #{@pid_path} for writing:\n\t" +
          "(#{e.class}) #{e.message}"
      exit!
    end
  end

  def get_pid
    pid = nil
    open(@pid_path, 'r') do |f|
      pid = f.readline.to_s.gsub(/[^0-9]/,'')
    end
    pid.to_i
  rescue Errno::ENOENT => e
    nil
  end

  def remove_pidfile
    File.unlink(@pid_path)
  rescue => e
    STDERR.puts "ERROR: Unable to unlink #{path}:\n\t" +
      "(#{e.class}) #{e.message}"
    exit
  end

  def process_exists?
    pid = get_pid
    return false unless pid
    Process.kill(0, pid)
    true
  rescue Errno::ESRCH, TypeError # "PID is NOT running or is zombied
    false
  rescue Errno::EPERM
    STDERR.puts "No permission to query #{pid}!";
    false
  end

  def stop
    pid = get_pid
    Process.kill("TERM", pid)
    remove_pidfile
  rescue Errno::ESRCH
    abort "No process to kill"
  end

  def start
    abort "Process already running!" if process_exists?
    if pid = Spoon.spawnp(@script)
      create_pid(pid)
    else
      Process.setsid
    end
  end
end