Alex Vollmer

…umm, no, actually not so much.

Instead, this is just a humble little notice about a humble little gem I put together today. It's called daemon-spawn and despite its simply terrifying name, it's really here to help all mankind. You see, I've been working like mad to stuff Merb smack-dab in the middle of an embedded Jetty project I've been working on. One of the last things I needed was a decent daemon-launcher/management gem-thingie to make it happen.

I cast about for an existing solution and found each a little lacking. The daemons gem had the executable name hard-wired to the output log name and didn't give me a clean way to specify additional arguments to JRuby (unless I wrote another wrapper script, to which I say "boo, hiss"). Then I looked at simple-daemon which seemed really promising. It was really really close to what I wanted but didn't extend very well as it required more and more class-methods. Yuck. I looked at daemon_generator, but it was very Rails-y and wanted to generate a bunch of code for me, which I didn't need. So I did what any honest, hard-working Ruby-dork does, and made my own!

It's simple—dead simple. Wanna see how simple? Here's a real-live echo server with daemon support:

#!/usr/bin/env ruby

require 'daemon-spawn'
require 'socket'

class EchoServer << DaemonSpawn::Base

  attr_accessor :server_socket

  def start(args)
    port = args.empty? ? 0 : args.first.to_i
    self.server_socket = TCPServer.new('127.0.0.1', port)
    port = self.server_socket.addr[1]
    puts "EchoServer started on port #{port}"
    loop do
      begin
        client = self.server_socket.accept
        while str = client.gets
          client.write(str)
        end
      rescue Errno::ECONNRESET => e
        STDERR.puts "Client reset connection"
      end
    end
  end

  def stop
    puts "Stopping EchoServer..."
    self.server_socket.close if self.server_socket
  end
end

EchoServer.spawn!(:working_dir => File.join(File.dirname(__FILE__), '..'),
                  :log_file => '/tmp/echo_server.log',
                  :pid_file => '/tmp/echo_server.pid',
                  :sync_log => true,
                  :singleton => true)

But what if you have non-Ruby code you want to daemonize? Well my friends, that's what Kernel#exec is for and it works like a champ. See the README for the full details. And of course to view the README, you have to install the gem which means you have daemon-spawn in the bowels of your machine! Mwaaa haa haa haa! Oops…I've said too much…

In all seriousness though, I would like to thank the powers-that-be at work who were very gracious to let me open-source this. You should start seeing more of this kind of stuff from Evri soon. As always, your feedback, comments, critiques and patches are welcome.

Opening The Gates…of Hell!! comments

Alex
Vollmer