How to use Delayed Job to handle your Carrierwave processing

This tutorial builds on my previous post about how to add FFMPEG processing to Carrierwave. Here I will show you my attempt at being able to utilize Delayed::Job to do the heavy lifting of processing when uploading files using Carrierwave. Remember, this could probably use some improvement, but it is a great starting point. So lets begin. The first thing you will need to do is add Delayed::Job to your application:

# Gemfile
gem "delayed_job"

Next you need to create the migration and migrate the database:

rails generate delayed_job
rake db:migrate

Now we get to the good part. Lets create a module to include into Carrierwave that will support holding off on doing the processing until Delayed::Job gets around to it:

# lib/carrier_wave/delayed_job.rb
module CarrierWave
  module Delayed
    module Job
      module ActiveRecordInterface
        def delay_carrierwave
          @delay_carrierwave ||= true
        end

        def delay_carrierwave=(delay)
          @delay_carrierwave = delay
        end

        def perform
          asset_name = self.class.uploader_options.keys.first
          self.send(asset_name).versions.each_pair do |key, value|
            value.process_without_delay!
          end
        end

        private

        def enqueue
          ::Delayed::Job.enqueue self
        end
      end

      def self.included(base)
        base.extend ClassMethods
      end

      module ClassMethods
        def self.extended(base)
          base.send(:include, InstanceMethods)
          base.alias_method_chain :process!, :delay
          ::ActiveRecord::Base.send(
            :include,
            CarrierWave::Delayed::Job::ActiveRecordInterface
          )
        end

        module InstanceMethods
          def process_with_delay!(new_file)
            process_without_delay!(new_file) unless model.delay_carrierwave
          end
        end
      end
    end
  end
end

Awesome! Now we need to tie this into our Uploader:

# app/uploaders/asset_uploader.rb
require File.join(Rails.root, "lib", "carrier_wave", "ffmpeg")
require File.join(Rails.root, "lib", "carrier_wave", "delayed_job") # New

class AssetUploader < CarrierWave::Uploader::Base
  include CarrierWave::Delayed::Job # New
  include CarrierWave::FFMPEG

  # Choose what kind of storage to use for this
  uploader: storage :file

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "#{Rails.root}/uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  # Add a version, utilizing our processor
  version :bitrate_128k do
    process :resample => "128k"
  end
end

The last thing we have to do is update our model to queue up delayed job:

# app/models/asset.rb
class Asset < ActiveRecord::Base
  mount_uploader :asset, AssetUploader
  
  after_save :enqueue # New
end

There you have it. Now when you create a new Asset, associate a file, and save it, it shouldn’t run the processes, but instead create a Delayed::Job record. Then Delayed::Job should pick it up and run the processors on it. This may not be perfect, but at least its a start! Thanks for reading!

Create FFMPEG processor for Carrierwave in Rails 3

I have had the pleasure of working with the carrierwave gem recently (as opposed to paperclip), and I must say, I am quite the fan. Once major thing I missed however, was the available list of custom user plugins for it, unlike paperclip. I believe this is mostly due to how new and recent carrierwave is. That being said, I put together a simple example of a FFMPEG process that will allow me to resample the bitrate of a file. This should lay the ground work for other features as well. This example is using Rails 3, but should be easily adaptable for 2. Also, make sure you already have FFMPEG installed and running properly. So lets get started: First things first…we need to add the appropriate gems to our Gemfile:

# Gemfile
gem "carrierwave"
gem "streamio-ffmpeg"

Next is the meat and potatoes of this..the actual FFMPEG process for carrierwave. I choose to keep my plugin files in the directory lib/carrierwave. Make sure you have this path included in your application.rb file if you are using rails 3. Here is the code:

# lib/carrierwave/ffmpeg.rb
require "streamio-ffmpeg"
module CarrierWave
  module FFMPEG
    module ClassMethods
      def resample( bitrate )
        process :resample => bitrate
      end
    end
 
    def resample( bitrate )
      directory = File.dirname( current_path )
      tmpfile = File.join( directory, "tmpfile" )
      File.move( current_path, tmpfile )
      file = ::FFMPEG::Movie.new(tmpfile)
      file.transcode( current_path, :audio_bitrate => bitrate)
      File.delete( tmpfile )
    end
  end
end

Good. Now that we have the plugin coded up, we need to include it into our uploader. I already have one mounted to my Asset model. Here is what my AssetUploader now looks like:

# app/uploaders/asset_uploader.rb
require File.join(Rails.root, "lib", "carrier_wave", "ffmpeg")

class AssetUploader < CarrierWave::Uploader::Base
  include CarrierWave::FFMPEG # <= include the plugin
  
  # Choose what kind of storage to use for this uploader:
  storage :file

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "#{Rails.root}/uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end
 
  # Add a version, utilizing our processor
  version :bitrate_128k do
    process :resample => "128k"
  end
end

There! Now whenever you add a new file, it should fire off the processor and create a new version. I hope this help anyone still up in the air about how to put together their own plugin/process for carrierwave. Next I will demonstrate how to incorporate Delayed::Job to move these intensive tasks to the background!

%d bloggers like this: