I like CarrierWave. That being said, I don't like tying up app instances waiting for images to process.

This gem addresses that issue by disabling processing until a background process initiates it. It supports Delayed Job, Resque and Girl Friday.

There are currently two offerings for backgrounding upload tasks which are as follows;

Backgrounder::ORM::Base::process_in_background

This method stores the original file and does no processing or versioning. Optionally you can add a column to the database which will be set to nil when the background processing is complete.

Backgrounder::ORM::Base::store_in_background

This method does nothing to the file after it is cached which makes it super fast. It requires a column in the database which stores the cache location set by carrierwave. The drawback to using this method is the need for a central location to store the cached files. This leave heroku out. Heroku may deploy workers on separate servers from where your dyno cached the files. That being said, I only recommend using this method if you have full control over your temp storage directory.

These instructions assume you have previously set up CarrierWave and DelayedJob or Resque

In Rails, add the following your Gemfile:

gem 'carrierwave_backgrounder'

In your CarrierWave uploader file:

class AvatarUploader < CarrierWave::Uploader::Base
  include ::CarrierWave::Backgrounder::Delay

  #etc...
end

In your model:

mount_uploader :avatar, AvatarUploader
process_in_background :avatar

Optionally you can add a column to the database which will be set to nil when the background processing is complete.

add_column :users, :avatar_processing, :boolean

In your model:

mount_uploader :avatar, AvatarUploader
store_in_background :avatar

Add a column to the model you want to background which will store the temp file location:

add_column :users, :avatar_tmp, :string

If you need to process/store the upload immediately:

@user.process_<column>_upload = true

To overide the worker in cases where additional methods need to be called or you have app specific requirements, pass the worker class as the second argument:

process_in_background :avatar, MyAppsAwesomeProcessingWorker

Currently ActiveRecord is the default orm and I have not tested this with others but it should work by adding the following to your carrierwave initializer:

DataMapper::Model.send(:include, ::CarrierWave::Backgrounder::ORM::Base)
# or
Mongoid::Document::ClassMethods.send(:include, ::CarrierWave::Backgrounder::ORM::Base)
# or
Sequel::Model.send(:extend, ::CarrierWave::Backgrounder::ORM::Base)

Contributions are gladly accepted from those who use these orms.

Copyright (c) 2011 Larry Sprock

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