Update: this script, from September 2007, is a bit out-dated, you can get more info on official God gem website.

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After many ways to monitor Feevy updaters, we’re finally using God gem today to manage everything with Ruby on many platforms.

Documentation is really clear, and it’s easy to adapt it to your own code. The nicest point was to be able to control our non-daemonized updaters, and monitor them all in the same tool.

Here is our script:

require 'rubygems'
require 'god'

ROOT = File.dirname(__FILE__)

God.init do |god|
  god.pid_file_directory = "#{ROOT}/pids"
end

[*0...20].each do |updater|
  God.watch do |w|
    # watch with no pid_file attribute set
    w.name = "updater_#{updater}"
    w.interval = 30.seconds # default
    w.start = "ruby #{ROOT}/updater.rb"
    w.grace = 10.seconds

    w.behavior(:clean_pid_file)

    w.start_if do |start|
      start.condition(:process_running) do |c|
        c.interval = 5.seconds
        c.running = false
      end
    end

    w.restart_if do |restart|
      restart.condition(:memory_usage) do |c|
        c.above = 150.megabytes
        c.times = [3, 5] # 3 out of 5 intervals
      end

      restart.condition(:cpu_usage) do |c|
        c.above = 50.percent
        c.times = 5
      end
    end
  end
end

[updated]: thanks to apeiros on irc://#ruby@irc.freenode.net for quick array initialization tips!