have destroying user executed as a background task

* using delayed_job as the gem for that
* this could also be used for other background-jobs that are currently implemented using cron

Gemfile

@@ -8,6 +8,7 @@ gem "rubytree", "~> 0.5.2", :require => 'tree'
 gem "rdoc", ">= 2.4.2"
 # Needed only on RUBY_VERSION = 1.8, ruby 1.9+ compatible interpreters should bring their csv
 gem "fastercsv", "~> 1.5.0", :platforms => [:ruby_18, :jruby, :mingw_18]
+gem 'delayed_job', "~>2.0.4"
 
 group :test do
   gem 'shoulda', '~> 2.10.3'

Rakefile

@@ -15,3 +15,9 @@ rescue LoadError
 end
 
 require 'tasks/rails'
+
+begin
+  require 'delayed/tasks'
+rescue LoadError
+  STDERR.puts "Run `rake gems:install` to install delayed_job"
+end

app/controllers/users_controller.rb

@@ -209,7 +209,8 @@ class UsersController < ApplicationController
   end
 
   def destroy
-    @user.destroy
+    # as destroying users is a lengthy process we handle it in the background
+    @user.send_later(:destroy)
 
     flash[:notice] = l('account.deleted')
     logged_user = nil

config/initializers/delayed_job_config.rb

@@ -0,0 +1 @@
+Delayed::Worker.logger = Rails.logger

db/migrate/20120529090411_create_delayed_jobs.rb

@@ -0,0 +1,21 @@
+class CreateDelayedJobs < ActiveRecord::Migration
+  def self.up
+    create_table :delayed_jobs, :force => true do |table|
+      table.integer  :priority, :default => 0      # Allows some jobs to jump to the front of the queue
+      table.integer  :attempts, :default => 0      # Provides for retries, but still fail eventually.
+      table.text     :handler                      # YAML-encoded string of the object that will do work
+      table.text     :last_error                   # reason for last failure (See Note below)
+      table.datetime :run_at                       # When to run. Could be Time.zone.now for immediately, or sometime in the future.
+      table.datetime :locked_at                    # Set when a client is working on this object
+      table.datetime :failed_at                    # Set when all retries have failed (actually, by default, the record is deleted instead)
+      table.string   :locked_by                    # Who is working on this object (if locked)
+      table.timestamps
+    end
+	
+    add_index :delayed_jobs, [:priority, :run_at], :name => 'delayed_jobs_priority'
+  end
+  
+  def self.down
+    drop_table :delayed_jobs  
+  end
+end

script/delayed_job

@@ -0,0 +1,5 @@
+#!/usr/bin/env ruby
+
+require File.expand_path(File.join(File.dirname(__FILE__), '..', 'config', 'environment'))
+require 'delayed/command'
+Delayed::Command.new(ARGV).daemonize