Best Practice For Background Processes

rubyonrails-talk
1

I have a couple background processes that run from anywhere between 2 seconds and 30 seconds that run periodically (some run every 15 minutes, some every 4 hrs). To run them I call a webpage using curl in a cron job. I have a funny feeling this is not the best thing to do :-).

All the tasks I have manipulate the DB. Either re-weighing users or copying data from one table to another.

What are the best practices to run these types of periodic tasks?

Thanks before hand for your feedback!

Your friend,

John

2

Here is what I do:

I have a file lib/offline/model_loader.rb that looks like this:

module ModelLoader

  def load_model(model_path=nil, database_config=nil, environment=nil)     model_path ||= "/../../app/models/"     database_config ||= "/../../config/database.yml"     environment ||= "development"     $LOAD_PATH << File.expand_path(File.dirname(__FILE__) + model_path)     require "yaml"     require "rubygems"     gem "activerecord"     require File.dirname(__FILE__) + '/../../config/environment'     conf = YAML::load(File.open(File.dirname(__FILE__) + database_config))     ActiveRecord::Base.establish_connection(conf[environment])   end

end

Then in whatever script you wanna run say script/my_site_name/ some_script_for_cron.rb

#!/usr/bin/env ruby

rootd = File.dirname(__FILE__) + '/../../' require rootd + 'lib/offline/model_loader' include ModelLoader ModelLoader::load_model(nil, nil, 'development')

# now you have access to all your models

MyModel.find(:all).each do |instance| ... ... end

There are other situations that may call for access to controllers/ views, there's a solution for that as well, but I suspect this is what you need.

Hope that helps, good luck! Tim

3

this is a perfect place for rake!

i encounter situations like this all the time at work. simply take the code from your action that you are hitting with curl and wrap them in a rake task. then set up your cron job to do something along the lines of:

15 2 * * * /usr/local/bin/rake -f /var/www/site/Rakefile do:something RAILS_ENV=production

and in lib/tasks/something.rake:

namespace :do do   desc "does something"   task :something => :environment do     <code moved from the action in your controller to here>   end end