Light-daemon is a ruby gem. It could help developers quickly build a daemon which preforks worker processes and monitors them.

gem install light-daemon

The usage is very simple:

require 'rubygems'
require 'light_daemon'

class Client
  def initialize
  end

  def call
    `echo "process: #{Process.pid}" >> /tmp/light-daemon.txt`
    sleep 3
    true
  end
end

LightDaemon::Daemon.start(Client.new, :children=> 2, :pid_file => "/tmp/light-daemon.pid")

What you need to do is:

1. Create your worker class. Define a method “call” and put the real work into it.

2. The method “call” needs to return true for the daemon to continuously call it.

3. You need to tell the daemon how many worker processes you want and a filename for daemon to store the PID of the daemon process.

4. If the method “call” returns false, the daemon will kill this worker process and create a new one. This would be very helpful if your code might have memory leaking and you want it to restart after certain criteria is met. An example is as following:

   require 'rubygems'
   require 'light_daemon'
   
   class Client
     def initialize
       @count = 0
     end
   
     def call
       `echo "process: #{Process.pid}" >> /tmp/light-daemon.txt`
       sleep 3
       @count +=1
       (@count < 100)? true : false
     end
   end
   
   LightDaemon::Daemon.start(Client.new, :children=> 2, :pid_file => "/tmp/light-daemon.pid" )
   

Copyright © 2012 [Yi Zhang], released under the MIT license