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https://github.com/lardawge/carrierwave_backgrounder

Offload CarrierWave's image processing and storage to a background process using ActiveJob or Sidekiq..
https://github.com/lardawge/carrierwave_backgrounder

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Offload CarrierWave's image processing and storage to a background process using ActiveJob or Sidekiq..

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# CarrierWave Backgrounder



[![Build Status](https://app.travis-ci.com/lardawge/carrierwave_backgrounder.svg?branch=master)](https://app.travis-ci.com/lardawge/carrierwave_backgrounder)

[![Code Climate](https://codeclimate.com/github/lardawge/carrierwave_backgrounder.png)](https://codeclimate.com/github/lardawge/carrierwave_backgrounder)



NOTICE: Version 1.0.0 contains breaking changes if you are coming from an earlier version.

The most notible change is the removal of queue backend options other than active_job and sidekiq.

If you are using other backends, switch over to active_job which should support your preference.

If you are using Sidekiq, there is nothing to change.



I am a fan of CarrierWave. That being said, I don't like tying up requests waiting for images to process.



This gem addresses that by offloading processing or storaging/processing to a background task.

We currently support ActiveJob and Sidekiq.



## Background options



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



```ruby

# This stores the original file with no processing/versioning.

# It will upload the original file to s3.

# This was developed to use in cases where you do not have access to the cached location such as Heroku.



Backgrounder::ORM::Base::process_in_background

```



```ruby

# This does nothing to the file after it is cached which makes it fast.

# It requires a column in the database which stores the cache location set by carrierwave so the background job can access it.

# The drawback to using this method is the need for a central location to store the cached files.

#

# IMPORTANT: Only use this method if you have full control over your tmp storage directory and can mount it on every deployed server.



Backgrounder::ORM::Base::store_in_background

```



## Installation and Usage



These instructions assume you have previously set up [CarrierWave](https://github.com/jnicklas/carrierwave) and your queuing lib of choice.



Take a look at the [Rails app](spec/support/dummy_app) to see examples of setup.



In Rails, add the following your Gemfile:



```ruby

gem 'carrierwave_backgrounder'

```



Run the generator which will create an initializer in config/initializers.

```bash

rails g carrierwave_backgrounder:install

```



You can pass additional configuration options to Sidekiq:



```ruby

CarrierWave::Backgrounder.configure do |c|

  c.backend :sidekiq, queue: :awesome_queue, size: 3

end

```



**IMPORTANT FOR SIDEKIQ BACKEND** - carrierwave (default queue name) should be added to your queue list or it will not run:



```yml

:queues:

  - [carrierwave, 1]

  - default

```



In your CarrierWave uploader file you will need to add a cache directory as well as change cache_storage to File:



```ruby

class AvatarUploader < CarrierWave::Uploader::Base

  include ::CarrierWave::Backgrounder::Delay



  # This is required if you are using S3 or any other remote storage.

  # CarrierWave's default is to store the cached file remotely which is slow and uses bandwidth.

  # By setting this to File, it will only store on saving of the record.

  cache_storage CarrierWave::Storage::File



  # It is recommended to set this to a persisted location if you are using `::store_in_background`.

  def cache_dir

    "path/that/persists"

  end



  #etc...

end

```



### To use process_in_background



In your model:



```ruby

mount_uploader :avatar, AvatarUploader

process_in_background :avatar

```



Optionally you can add a column to the database which will be set to `true` when

the background processing has started and to `false` when the background processing is complete.



This is set to true in the after_commit hook when the job is created. It is very useful if you are waiting to notify the user of completion.



```ruby

add_column :users, :avatar_processing, :boolean, null: false, default: false

```



### To use store_in_background



In your model:



```ruby

mount_uploader :avatar, AvatarUploader

store_in_background :avatar

```



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



```ruby

add_column :users, :avatar_tmp, :string

```



## Usage Tips



### Bypass backgrounding

If you need to process/store the upload immediately:



```ruby

@user.process__upload = true

```



This must be set before you assign an upload:



```ruby

@user = User.new

@user.process_avatar_upload = true

@user.attributes = params[:user]

```



### Override worker

To override 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:



```ruby

process_in_background :avatar, MyParanoidWorker

```



Then create a worker that subclasses carrierwave_backgrounder's worker.

Each method, #store_in_background and #process_in_background has there own worker.



#### For Sidekiq

`process_in_background` subclass `::CarrierWave::Workers::ProcessAsset`

`store_in_background` subclass `::CarrierWave::Workers::StoreAsset`



#### For ActiveJob

`process_in_background` subclass `::CarrierWave::Workers::ActiveJob::ProcessAsset`

`store_in_background` subclass `::CarrierWave::Workers::ActiveJob::StoreAsset`



```ruby

# Sidekiq Example



class User < ActiveRecord::Base

  mount_uploader :avatar, AvatarUploader

  process_in_background :avatar, MyParanoidWorker

end



class MyParanoidWorker < ::CarrierWave::Workers::ProcessAsset

  # ...or subclass CarrierWave::Workers::StoreAsset if you're using store_in_background



  def error(job, exception)

    report_job_failure  # or whatever

  end



  # other hooks you might care about

end

```



```ruby

# ActiveJob Example



class User < ActiveRecord::Base

  mount_uploader :avatar, AvatarUploader

  process_in_background :avatar, MyActiveJobWorker

end



class MyActiveJobWorker < ::CarrierWave::Workers::ActiveJob::StoreAsset

  after_perform do

    # your code here

  end

end

```



### Testing with Rspec

We use the after_commit hook when using active_record. This creates a problem when testing with Rspec because after_commit never gets fired

if you're using transactional fixtures. One solution to the problem is to use the [TestAfterCommit gem](https://github.com/grosser/test_after_commit).

There are various other solutions in which case google is your friend.



## License



Copyright (c) 2011 Larry Sprock



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 PURPOSE AND

NONINFRINGEMENT. IN NO EVENT SHALL 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.