RackServer thin with god (cluster multi processes)

thin.god

# http://god.rubyforge.org/
# http://unicorn.bogomips.org/SIGNALS.html
# http://railscasts.com/episodes/130-monitoring-with-god

rails_env = ENV['RAILS_ENV'] || 'production'
rails_appname = ENV['RAILS_APPNAME'] || 'appname'
rails_root = ENV['RAILS_ROOT'] || "/opt/deploy/#{rails_appname}/current"
num_workers   = rails_env == 'production' ? 8 : 1
thin_rootport   = 3000

def generic_monitoring(w, options = {})
# generic_monitoring option list
# option list
# [:start_grace], [:stop_grace], [:restart_grace]
# [:cpu_interval], [:cpu_limit], [:memory_interval], [:memory_limit], [:contact]

  w.start_grace   = options[:start_grace]
  w.stop_grace    = options[:stop_grace]
  w.restart_grace = options[:restart_grace]

  # determine the state on startup
  w.transition(:init, { true => :up, false => :start }) do |on|
    on.condition(:process_running) do |c|
      c.running = true
      c.notify  = options[:contact]
    end
  end

  # determine when process has finished starting
  w.transition([:start, :restart], :up) do |on|
    on.condition(:process_running) do |c|
      c.running = true
      c.notify  = options[:contact]
    end
    
    # failsafe
    on.condition(:tries) do |c|
      c.times = 5
      c.transition = :start
      c.notify  = options[:contact]
    end
  end


  # start if process is not running
  w.transition(:up, :start) do |on|
    on.condition(:process_exits) do |c|
      c.notify  = options[:contact]
    end
  end

  # restart if memory or cpu is too high
  w.transition(:up, :restart) do |on|
    on.condition(:memory_usage) do |c|
      c.interval = options[:memory_interval]
      c.above = options[:memory_limit]
      c.times = [3, 5]
      c.notify  = options[:contact]
    end
    
    on.condition(:cpu_usage) do |c|
      c.interval = options[:cpu_interval]
      c.above = options[:cpu_limit]
      c.times = [3, 5]
      c.notify  = options[:contact]
    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
      c.notify  = options[:contact]
    end
  end

end


num_workers.times do |num|
  God.watch do |w|
    port = thin_rootport + num
    w.name = "#{rails_appname}_thin_#{port}"
    w.group = "#{rails_appname}"
    w.interval = 5.seconds
    w.dir = rails_root
    w.pid_file = File.join(rails_root, "/tmp/pids/thin.#{port}.pid")
  
    w.start = "bundle exec thin -R ./thin_#{rails_appname}.ru -e #{rails_env} -s #{num_workers} -p #{thin_rootport} -o #{num} -d start"
  
    # QUIT gracefully shuts down workers
    w.stop = "bundle exec thin -s #{num_workers} -p #{thin_rootport} -o #{num} stop"
    # w.stop_signal = 'QUIT'
  
    # or god signal USR2 #{app}
    w.restart = "bundle exec thin -R ./thin_#{rails_appname}.ru -e #{rails_env} -s #{num_workers} -p #{thin_rootport} -o #{num} restart"
    
    w.uid = 'root'
    w.gid = 'root'
  
    w.behavior(:clean_pid_file)
  
    # generic_monitoring option list
    # [:start_grace], [:stop_grace], [:restart_grace]
    # [:cpu_interval], [:cpu_limit], [:memory_interval], [:memory_limit], [:contact]
    generic_monitoring(w,
                       :start_grace =>      10.seconds,
                       :stop_grace =>       10.seconds,
                       :restart_grace =>    10.seconds,
                       :cpu_interval =>     60.seconds,
                       :cpu_limit =>        30.percent,
                       :memory_interval =>  60.seconds,
                       :memory_limit =>    200.megabytes,
                       :contact =>          'mailto',
                      )
  
  end
end