Starting background tasks with Capistrano

Question

For my RubyOnRails-App I have to start a background job at the end of Capistrano deployment. For this, I tried the following in deploy.rb:

run "nohup #{current_path}/script/runner -e production 'Scheduler.start' &", :pty => true

Sometimes this works, but most of the time it does not start the process (= not listed in ps -aux). And there are no error messages. And there is no nohup.out, not in the home directory and not in the rails app directory.

I tried using trap('SIGHUP', 'IGNORE') in scheduler.rb instead of nohup, but the result is the same.

The only way to get it work is removing the ":pty => true" and do a manual Ctrl-C at the end of "cap deploy". But I don't like this...

Are there any other chances to invoke this Scheduler.start? Or to get some more error messages?

I'm using Rails 2.3.2, Capistrano 2.5.8, Ubuntu Hardy on the Server

Answer 1

Do you want your Scheduler job to run continually in the background and get restarted when you run Capistrano?

If so, then for that I use runit http://smarden.sunsite.dk/runit/ and DelayedJob http://github.com/Shopify/delayed_job/tree/master

1. Install runit in the mode of not replacing init
2. Add your background job as a runit service and add the log monitor for it from runit.
3. Have Capistrano call sudo sv kill job_name to kill and restart the job.

My backround job is an instance of the Rails plugin DelayedJob which handles background Rails tasks. I kill it with every Capistrano deploy so it will restart with the updated code base.

This has proved to be very reliable.

HTH,

Larry