Utilize S3 as a storage mechanism for Rails assets

tddium.rake

namespace :tddium do
  class AssetS3

    BUCKET = "tddium_assets"
    KEEP_AROUND = 7.days

    def initialize(branch)
      @branch = branch
    end

    def pre    
      download_branch_assets
    end

    def post
      upload_branch_assets
      clean_old_branches
    end

    protected

    def download_branch_assets
      object = s3_object
      object = s3_object('master') unless object.exists?
      return unless object.exists?

      ensure_directories_exists

      File.open(gzip_path, 'wb') do |io|
        object.read do |chunk|
          io.write(chunk)
        end
      end

      `cd #{asset_path} && tar -zxvf #{gzip_path} -C ./`
    end

    def upload_branch_assets
      
      ensure_directories_exists

      `cd #{asset_path} && tar -zcvf #{gzip_path} ./`
      
      object = s3_object
      file = File.open(gzip_path, 'r')
      object.write(file, :content_encoding => 'utf-8')
    end


    def clean_old_branches
      bucket.objects.each do |object|
        last_mod = object.last_modified rescue nil
        if last_mod && last_mod < KEEP_AROUND.ago
          object.delete
        end
      end
    end




    def s3
      @s3 ||= begin
        s3_config = YAML.load_file("#{Rails.root}/config/s3.yml")['test']
        AWS::S3.new(
          :access_key_id => s3_config['access_key_id'],
          :secret_access_key => s3_config['secret_access_key']
        )
      end
    end

    def bucket
      @bucket ||= begin
        s3.buckets.create(BUCKET)
        s3.buckets[BUCKET]
      end
    end 

    def s3_object(branch_name = @branch)
      bucket.objects["#{branch_name}.tar.gz"]
    end


    def ensure_directories_exists
      `mkdir -p #{asset_path}`
      `mkdir -p tmp`
    end


    def gzip_path
      Rails.root.join('tmp', 'assets.tar.gz')
    end

    def asset_path
      prefix = Rails.application.config.assets.prefix.gsub(/^\//, '')
      Rails.root.join('public', prefix)
    end


  end

  desc "Download S3 Assets"
  task :download_assets => :environment do
    AssetS3.new(get_current_branch).pre
  end

  desc "Upload S3 Assets"
  task :upload_assets => :environment do
    AssetS3.new(get_current_branch).post
  end
 desc "pre_hook"
  task :pre_hook do
    Rake::Task['tddium:download_assets'].invoke

    puts 'precompiling assets'
    Rake::Task['assets:precompile'].invoke
  end

  desc "post_build_hook"
  task :post_build_hook do
    tag_green_build
    Rake::Task['tddium:upload_assets'].invoke
  end

  def get_current_branch
    `git symbolic-ref HEAD 2>/dev/null | cut -d"/" -f 3-`.strip
  end

end