Symlink Locker

symlink_locker.rb

class Locker
  def initialize(lockname)
    @lockname = lockname
    @lockpath = "/tmp/#{lockname}"
    @mylock = "#{@lockpath}.#{Process.pid}"
    @havelock = false
  end

  def lock
    do_lock
    if block_given?
      yield
      unlock
    end
  end

  def unlock
    raise "I don't have lock" if !@havelock

    FileUtils.rm(@lockpath)
    FileUtils.rm(@mylock)
    @havelock = false
  end

  private
  def do_lock
    if File.exist?(@lockpath)
      return false 
    end

    begin
      FileUtils.touch(@mylock)
      FileUtils.ln_s(@mylock, @lockpath)
    rescue Errno::ENOTDIR
      # failed to obtain lock
      FileUtils.rm(@mylock)
    else
      @havelock = true
    end
  end
end