Shane Sveller

On my home server I’m toying with some Rails clustering and such, using nginx and thin, and now God to watch over things.
With this setup, I can add apps and port-ranges to monitor any time I like, and I can split off a particularly specific configuration group if an app has unusual trends or requirements, such as using loads of memory.

RAILS_ROOT = "/var/www/rails"

APPS = {
  "redmine" => %w{5000 5001 5002 5003 5004},
  "typo5" => %w{4000 4001 4002}
  }

for app in APPS.keys
  for port in APPS[app]
    God.watch do |w|
      w.name = "#{app}-thin-#{port}"
      w.interval = 30.seconds # default
      w.start = "thin start -C #{RAILS_ROOT}/#{app}/config/thin.yml -o #{port}"
      w.stop = "thin stop -C #{RAILS_ROOT}/#{app}/config/thin.yml -o #{port}"
      w.restart = "thin restart -C #{RAILS_ROOT}/#{app}/config/thin.yml -o #{port}"
      w.start_grace = 10.seconds
      w.restart_grace = 10.seconds
      w.pid_file = File.join(RAILS_ROOT, "/#{app}/tmp/pids/thin.#{port}.pid")

      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 = 80.megabytes
          c.times = [3, 5] # 3 out of 5 intervals
        end

        restart.condition(:cpu_usage) do |c|
          c.above = 50.percent
          c.times = 3
        end
      end

      # lifecycle
      w.lifecycle do |on|
        on.condition(:flapping) do |c|
          c.to_state = [:start, :restart]
          c.times = 5
          c.within = 5.minute
          c.transition = :unmonitored
          c.retry_in = 10.minutes
          c.retry_times = 5
          c.retry_within = 2.hours
        end
      end
    end
  end
end