Delaying the metreics calculation with delayedJob. (Thiago & Joao)

Author: thiago rodrigues colucci

Diff for: Rakefile

@@ -8,3 +8,11 @@ require 'rake/testtask'
 require 'rake/rdoctask'
 
 require 'tasks/rails'
+
+begin
+  require 'delayed_job'
+  require 'delayed/tasks'
+rescue LoadError
+  STDERR.puts "Run `rake gems:install` to install delayed_job"
+end
+

Diff for: app/models/project.rb

@@ -19,12 +19,10 @@ def calculate_metrics
         update_attribute :svn_error, error.error_message
       end
   end
+  
 
   def asynchronous_calculate_metrics
-#    pid = Kernel.fork do
-      calculate_metrics
- #   end
-  #  Process.detach pid
+    Delayed::Job.enqueue CalculateMetricsJob.new(id)
   end
 
   def download_source_code

Diff for: config/environment.rb

@@ -25,6 +25,7 @@
   config.gem "webrat", :lib => false, :version => ">= 0.7.0"
   config.gem "database_cleaner", :lib => false, :version => ">= 0.5.0"
   config.gem "authlogic"
+  config.gem 'delayed_job'
   # Only load the plugins named here, in the order given (default is alphabetical).
   # :all can be used as a placeholder for all plugins not explicitly named
   # config.plugins = [ :exception_notification, :ssl_requirement, :all ]

Diff for: db/migrate/010_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

Diff for: db/schema.rb

@@ -9,7 +9,22 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 9) do
+ActiveRecord::Schema.define(:version => 10) do
+
+  create_table "delayed_jobs", :force => true do |t|
+    t.integer  "priority",   :default => 0
+    t.integer  "attempts",   :default => 0
+    t.text     "handler"
+    t.text     "last_error"
+    t.datetime "run_at"
+    t.datetime "locked_at"
+    t.datetime "failed_at"
+    t.string   "locked_by"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+  end
+
+  add_index "delayed_jobs", ["priority", "run_at"], :name => "delayed_jobs_priority"
 
   create_table "metrics", :force => true do |t|
     t.string   "name"

Diff for: 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

Diff for: spec/models/project_spec.rb

@@ -247,17 +247,16 @@ def valid_analizo_hash(attributes={})
     end
   end
 
-  it "should calculates metrics on create" do
+  it "should order to calculate metrics on create" do
     require 'resources/project_mock'
     project_mock = ProjectMock.new valid_project_attributes
-    project_mock.called_calculate_metrics.should be_false
     project_mock.save
-    project_mock.called_calculate_metrics.should be_true
+    project_mock.called_asynchronous_calculate_metrics
   end
 
   it "should save in database metrics calculated" do
     project = Project.create valid_project_attributes
-    
+    project.calculate_metrics
     Metric.find_by_project_id(project.id).should_not be_nil
   end
 

Diff for: spec/resources/project_mock.rb

@@ -1,12 +1,17 @@
 class ProjectMock < Project
-  attr_reader :called_calculate_metrics
+  attr_reader :called_calculate_metrics, :called_asynchronous_calculate_metrics
 
   def initialize params
     super params
     @called_calculate_metrics = false
+    @called_asynchronous_calculate_metrics = false
   end
 
   def calculate_metrics
     @called_calculate_metrics = true
   end
-end
+
+  def asynchronous_calculate_metrics
+    @called_asynchronous_calculate_metrics = true
+  end
+end

Diff for: vendor/plugins/delayed_job/MIT-LICENSE

@@ -0,0 +1,20 @@
+Copyright (c) 2005 Tobias Luetke
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOa AND
+NONINFRINGEMENT. IN NO EVENT SaALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Diff for: vendor/plugins/delayed_job/README.textile

@@ -0,0 +1,206 @@
+h1. Delayed::Job
+
+Delated_job (or DJ) encapsulates the common pattern of asynchronously executing longer tasks in the background. 
+
+It is a direct extraction from Shopify where the job table is responsible for a multitude of core tasks. Amongst those tasks are:
+
+* sending massive newsletters
+* image resizing
+* http downloads
+* updating smart collections
+* updating solr, our search server, after product changes
+* batch imports 
+* spam checks 
+
+h2. Installation
+
+To install as a gem, add the following to @config/environment.rb@:
+
+<pre>
+config.gem 'delayed_job'
+</pre>
+
+Rake tasks are not automatically loaded from gems, so you'll need to add the following to your Rakefile:
+
+<pre>
+begin
+  require 'delayed/tasks'
+rescue LoadError
+  STDERR.puts "Run `rake gems:install` to install delayed_job"
+end
+</pre>
+
+To install as a plugin:
+
+<pre>
+script/plugin install git://github.com/collectiveidea/delayed_job.git
+</pre>
+
+After delayed_job is installed, you will need to setup the backend.
+
+h2. Backends
+
+delayed_job supports multiple backends for storing the job queue. There are currently implementations for Active Record, MongoMapper, and DataMapper.
+
+h3. Active Record
+
+The default is Active Record, which requires a jobs table.
+
+<pre>
+$ script/generate delayed_job
+$ rake db:migrate
+</pre>
+
+h3. MongoMapper
+
+<pre>
+# config/initializers/delayed_job.rb
+Delayed::Worker.backend = :mongo_mapper
+</pre>
+
+h3. DataMapper
+
+<pre>
+# config/initializers/delayed_job.rb
+Delayed::Worker.backend = :data_mapper
+Delayed::Worker.backend.auto_upgrade!
+</pre>
+
+h2. Queuing Jobs
+
+Call @.delay.method(params)@ on any object and it will be processed in the background.
+
+<pre>
+# without delayed_job
+Notifier.deliver_signup(@user)
+
+# with delayed_job
+Notifier.delay.deliver_signup @user
+</pre>
+
+If a method should always be run in the background, you can call @#handle_asynchronously@ after the method declaration:
+
+<pre>
+class Device
+  def deliver
+    # long running method
+  end
+  handle_asynchronously :deliver
+end
+
+device = Device.new
+device.deliver
+</pre>
+
+h2. Running Jobs
+
+@script/delayed_job@ can be used to manage a background process which will start working off jobs.  Make sure you've run `script/generate delayed_job`.
+
+<pre>
+$ RAILS_ENV=production script/delayed_job start
+$ RAILS_ENV=production script/delayed_job stop
+
+# Runs two workers in separate processes.
+$ RAILS_ENV=production script/delayed_job -n 2 start
+$ RAILS_ENV=production script/delayed_job stop
+</pre>
+
+Workers can be running on any computer, as long as they have access to the database and their clock is in sync. Keep in mind that each worker will check the database at least every 5 seconds.
+
+You can also invoke @rake jobs:work@ which will start working off jobs. You can cancel the rake task with @CTRL-C@. 
+
+h2. Custom Jobs
+
+Jobs are simple ruby objects with a method called perform. Any object which responds to perform can be stuffed into the jobs table. Job objects are serialized to yaml so that they can later be resurrected by the job runner. 
+
+<pre>
+class NewsletterJob < Struct.new(:text, :emails)
+  def perform
+    emails.each { |e| NewsletterMailer.deliver_text_to_email(text, e) }
+  end    
+end  
+  
+Delayed::Job.enqueue NewsletterJob.new('lorem ipsum...', Customers.find(:all).collect(&:email))
+</pre>
+
+You can also add an optional on_permanent_failure method which will run if the job has failed too many times to be retried:
+
+<pre>
+class ParanoidNewsletterJob < NewsletterJob
+  def perform
+    emails.each { |e| NewsletterMailer.deliver_text_to_email(text, e) }
+  end    
+
+  def on_permanent_failure
+    page_sysadmin_in_the_middle_of_the_night
+  end
+end  
+</pre>
+
+h2. Gory Details
+
+The library evolves around a delayed_jobs table which looks as follows: 
+
+<pre>
+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
+</pre>
+
+On failure, the job is scheduled again in 5 seconds + N ** 4, where N is the number of retries.
+
+The default Worker.max_attempts is 25. After this, the job either deleted (default), or left in the database with "failed_at" set.
+With the default of 25 attempts, the last retry will be 20 days later, with the last interval being almost 100 hours.
+
+The default Worker.max_run_time is 4.hours. If your job takes longer than that, another computer could pick it up. It's up to you to
+make sure your job doesn't exceed this time. You should set this to the longest time you think the job could take.
+
+By default, it will delete failed jobs (and it always deletes successful jobs). If you want to keep failed jobs, set
+Delayed::Worker.destroy_failed_jobs = false. The failed jobs will be marked with non-null failed_at.
+
+Here is an example of changing job parameters in Rails:
+
+<pre>
+# config/initializers/delayed_job_config.rb
+Delayed::Worker.destroy_failed_jobs = false
+Delayed::Worker.sleep_delay = 60
+Delayed::Worker.max_attempts = 3
+Delayed::Worker.max_run_time = 5.minutes
+</pre>
+
+h3. Cleaning up
+
+You can invoke @rake jobs:clear@ to delete all jobs in the queue.
+
+h2. Mailing List
+
+Join us on the mailing list at http://groups.google.com/group/delayed_job
+
+h2. How to contribute
+
+If you find what looks like a bug:
+
+# Check the GitHub issue tracker to see if anyone else has had the same issue.
+   http://github.com/collectiveidea/delayed_job/issues/
+# If you don't see anything, create an issue with information on how to reproduce it.
+
+If you want to contribute an enhancement or a fix:
+
+# Fork the project on github.
+   http://github.com/collectiveidea/delayed_job/
+# Make your changes with tests.
+# Commit the changes without making changes to the Rakefile, VERSION, or any other files that aren't related to your enhancement or fix
+# Send a pull request.
+
+h3. Changelog
+
+See http://wiki.github.com/collectiveidea/delayed_job/changelog for a list of changes.
+