Solving Background Processing with a Single, Generic Background Job

Again I read an article about background processing that generates many different jobs which all do the same: call method a on b with parameter z. At the moment we are using one GenericJob to handle all those cases.

It serializes ActiveRecord objects to a string representation, so that they do not get submittet as instance(often too large or deserialisation problems), if you do not need this feature, :send_later could be a good option for starting with generic jobs.

Usage

GenericJob.publish UserMailer, :deliver_notification,
  :args=>[user, comment], :priority=>2

Install

class GenericJob < DelayedJobBase
  DEFAULT_JOB_PRIORITY = 5

  # GenericJob.publish( Product, :find, :args=>[:all, {:conditions=>"1 = 2"}], :priority=>3 )
  def self.publish(klass, method, options={})
    args = options[:args] || []
    args = GenericJob.serialize_ar(args)
    priority = options[:priority] || DEFAULT_JOB_PRIORITY
    Delayed::Job.enqueue self.new(:class_name => klass.to_s, :method_name => method, :args => args), priority
  end

  def perform
    klass = message[:class_name].constantize
    args = GenericJob.deserialize_ar(message[:args]||[])
    klass.send(message[:method_name], *args)
  end

  private

  def self.serialize_ar(args)
    args.map do |arg|
      if arg.is_a?(ActiveRecord::Base)
        "ActiveRecord:#{arg.class}:#{arg.id}"
      else
        arg
      end
    end
  end

  def self.deserialize_ar(args)
    args.map do |arg|
      if arg.to_s =~ /^ActiveRecord:(\w+):(\d+)$/
        $1.constantize.find($2)
      else
        arg
      end
    end
  end
end

Ubuntu Karmic Koala is here, time for a fresh install

Since my old Ubuntu lived a long live and saw numerous hacks, I chose to reinstall from scratch, here are the steps I took:

1. install dotfiles
2. Skype
3. Multi-clipboard: sudo apt-get install glipper
4. Application laucher: sudo apt-get install gnome-do + enable skype plugin
5. Ruby enterprise
6. Rubymine + Desktop icon+ Meta key for Rubymine
7. Mysql: sudo apt-get install mysql-server mysql-client libmysql-ruby
8. Apache:  sudo apt-get install apache2 apache2-mpm-prefork apache2-prefork-dev
9. Passenger
10. SSL for apache/passenger
11. gem sources -a http://gems.github.com
12. gems…
13. Java: sudo apt-get install sun-java6-jre
14. Git: sudo apt-get install git-core

No more hacks, everything works, very fast startup (~10s), faster graphics (for intel chips)

My new desktop

SSL/HTTPS for Passenger in development on Ubuntu Jaunty

Making a certificate

sudo mkdir /etc/apache2/ssl
sudo /usr/sbin/make-ssl-cert /usr/share/ssl-cert/ssleay.cnf /etc/apache2/ssl/apache.pem

sudo nano /etc/apache2/sites-available/default-ssl
  #deactivete other crt/key files (snakeoil)
  SSLCertificateFile /etc/apache2/ssl/apache.pem

sudo a2ensite default-ssl
sudo a2enmod ssl
sudo /etc/init.d/apache2 restart

Configure passenger

<VirtualHost *:80>
 ServerAlias *.something.com
 RailsEnv development
 DocumentRoot /apps/something/public
</VirtualHost>
<VirtualHost *:443>
 SSLEngine on
 SSLCertificateFile /etc/apache2/ssl/apache.pem
 ServerAlias *.something.com
 RailsEnv development
 DocumentRoot /apps/something/public
</VirtualHost>

host

descriptive raise — tired of exception class/object expected ?

# descriptive raise
# normale: raise 1 == TypeError: exception class/object expected
# now: raise 1 == RuntimeError: 1
class Object
  def raise_with_helpfulness(*args)
    raise_without_helpfulness(*args)
  rescue TypeError => e
    raise_without_helpfulness args.first.inspect if e.to_s == 'exception class/object expected'
    raise e
  end
  alias_method_chain :raise, :helpfulness

Speeding up Slow Spork Startup for Rails 2.3+

If you noticed spork startup getting slower when switching to Rails 2.3, your not alone

• Views are eager loaded
• app/ is eager loaded (when config.cache_classes is on)

Without hack: 18s startup
With hack: 2s startup

Try it

#spec/spec_helper.rb
begin
  require 'spork/app_framework/rails'
  module Spork::AppFramework::Rails::NinjaPatcher
    # views are preloaded  spork must be restarted for view changes
    def delay_eager_view_loading
      puts "removed because i am too slow..."
    end

    # do not preload application files
    # alternatively urn off config.cache_classes
    def delay_app_preload
      ::Rails::Initializer.send(:define_method, :load_application_classes) do
      end
    end
  end
rescue
end

Spork.prefork do
  ...