Question

I have an ActiveRecord transaction that takes place during a web service call. It doesn’t need to be synchronous with the call and there is a delay while this transaction happens and the user sees a response from the server because ActiveRecord is busy creating object(s) and updating the db (while retaining a lock on a certain MyISAM table) + running all of its callbacks, etc.

What’s a good strategy to move this ActiveRecord create call so that it is not synchronously holding up the web service? I need to pass the create call parameters from a user session that is created in the action, so I’m not sure if an after_filter will make sense. Should I use a delayed job, messaging queue, or is an after_filter the best bet? If the answer is an after_filter, can I pass it parameters?

Answer 1

Use a delayed job.

Just add gem 'delayed_job' to your Gemfile, then run bundle install, rails g delayed_job and rake db:migrate.

Write a method on your user model that performs the stuff you want in the background, and tell it to always run in the background

# app/models/user.rb
def do_complex_stuff(session)
  ...
end
handle_asynchronously :do_complex_stuff

Finally, call that method from your controller:

# app/controllers/users_controller.rb
def create
   # do some stuff
   ...

   # fire off the delayed job
   current_user.do_complex_stuff(current_session)

   # do some more stuff
   ...
end

This should get you started. See https://github.com/collectiveidea/delayed_job for more info.