USAGE

As workerqueue is very flexible, there are many ways to use it.
Below we have some examples on how to could be used.

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> How can I handle file uploads that need to be processed? --------------------------------------------------------------------------------
We start by creating a ImportersController, which will handle the files.
  ruby script/generate controller importers

Open /app/controllers/importers_controller.rb
  Class ImportersController < ApplicationController
    # POST /importers
    def create
      if !params['upload']
        render :text => 'No file was uploaded!', :status => 400
        return
      end
    
      begin
        wq                  = WorkerQueue::WorkerQueueItem.new
        wq.task_group       = 'file_importer'
        wq.class_name       = 'Importer'
        wq.method_name      = 'parse'
        wq.task_name        = params['upload']['file'].original_filename
        wq.data             = params['upload']['file'].read
        wq.argument_hash    = { :original_filename =>
                                param['upload']['file'].original_filename
                              }
        work.skip_on_error  = false
        wq.save!

        render :text => "OK", :status => 200
      rescue Exception => e
        render :text => "ERROR", :status => 500
      end
    end
  end


If a file is posted to /importers, it is placed into the database.
When WorkerQueue.work is run, it executes the following command:
  Importer.parse( :original_filename => 'file1.xml',
                  :data => '<xml><a>somedata</a></xml>')

Because of the task group, WorkerQueue will only execute 1 parse task at the
time.  If files may be handled in parallel, remove the task_group line.

When a parse task fails, it will continue to store files in the database,
but stop processing them. If you do not want this, you can remove the
skip_after_error line.


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> Can I use WorkerQueue to generate reports in the background?
--------------------------------------------------------------------------------

Add the following code to the report controller:

  wq                = WorkerQueue::WorkerQueueItem.new
  wq.task_group     = User.current_user
  wq.task_name      = params['report_type']
  wq.class_name     = 'ReportGenerator'
  wq.method_name    = 'generate'
  wq.argument_hash  = {
                        :report_type => params['report_type'],
                        :period => params['period'],
                        :user => User.current_user
                      }
  wq.save!

When WorkerQueue.work is run, it executes the following command:
  ReportGenerator.generate( :report_type => :billing,
                            :period => '2008-10', :user => @bob)

With the task_group being the name of the user, the WorkerQueue will handle the report generation requests of user Bob
one after the other.


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> Can I autmatically clear unused sessions in my database?
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First we start by generating a sweep sessions loader.
ruby script/generate worker_queue_item_loader SweepSessions

Open up /lib/worker_queue/sweep_sessions_loader.rb and change it to the
following:

  Class SweepSessionsLoader < WorkerQueue::WorkerQueueItemLoader
    def self.prepare
      work.class_name     = 'Session'
      work.method_name    = 'sweep'
      work.argument_hash  = '20m'
    end
  end

If you change cron to call load and work, instead of just work WorkerQueue will
automatically sweep your sessions for you.

  rake workerqueue:load_and_work