Monitor a Rake task with God

In order to monitor a Rake task using God Show archive.org snapshot your Rake file must write a file with its process ID (PID) to a path determined by God. This way God can check whether the Rake process is still alive.

Here is how to do this: In your God config, call the Rake task with an environment variable PIDFILE. This variable should equal the PID file path desired by God:

God.watch do |w|
  w.dir = "#{rails_root}"
  w.name = "my_task"
  w.interval = 10.seconds
  w.pid_file = "#{rails_root}/tmp/pids/#{w.name}.pid"
  w.env = {"RAILS_ENV"=>rails_env, 'PIDFILE' => w.pid_file}
  w.start = "bundle exec rake my_task &"
  ...
end

Your Rake task should write its process ID to that PID file:

task :my_task => :environment do
  File.open(ENV['PIDFILE'], 'w') { |f| f << Process.pid } if ENV['PIDFILE']
  Model.perform_task!
end

Some advice

Don't let Ruby scripts run forever. You will run into many issues. Instead let your script terminate after some hours or X iterations and trust on God restarting the task.