Downloading and zipping files that were uploaded to S3 with CarrierWave - ruby-on-rails

Question

I have a small Rails 3.2.1 app that uses CarrierWave 0.5.8 for file uploads to S3 (using Fog)
I want users to be able to select some images that they'd like to download, then zip them up and send them a zip. Here is what I've come up with:
def generate_zip
#A collection of Photo objects. The Photo object has a PhotoUploader mounted.
photos = Photo.all
tmp_filename = "#{Rails.root}/tmp/" << Time.now.strftime('%Y-%m-%d-%H%M%S-%N').to_s << ".zip"
zip = Zip::ZipFile.open(tmp_filename, Zip::ZipFile::CREATE)
zip.close
photos.each do |photo|
file_to_add = photo.photo.file
zip = Zip::ZipFile.open(tmp_filename)
zip.add("tmp/", file_to_add.path)
zip.close
end
#do the rest.. like send zip or upload file and e-mail link
end
This doesn't work because photo.photo.file returns an instance of CarrierWave::Storage::Fog::File instead of a regular file.
EDIT: The error this leads to:
Errno::ENOENT: No such file or directory - uploads/photos/name.jpg
I also tried the following:
tmp_filename = "#{Rails.root}/tmp/" << Time.now.strftime('%Y-%m-%d-%H%M%S-%N').to_s << ".zip"
zip = Zip::ZipFile.open(tmp_filename, Zip::ZipFile::CREATE)
zip.close
photos.each do |photo|
processed_uri = URI.parse(URI.escape(URI.unescape(photo.photo.file.authenticated_url)).gsub("[", "%5B").gsub("]", "%5D"))
file_to_add = CarrierWave::Uploader::Download::RemoteFile.new(processed_uri)
zip = Zip::ZipFile.open(tmp_filename)
zip.add("tmp/", file_to_add.path)
zip.close
end
But this gives me a 403. Some help would be greatly appreciated.. It probably is not that hard I'm just Doing it Wrong™

Answer 1

I've managed to solve the problem with help from #ffoeg
The solution offered by #ffoeg didn't work quite so well for me since I was dealing with zip files > 500 MB which caused me problems on Heroku. I've therefor moved the zipping to a background process using resque:
app/workers/photo_zipper.rb:
require 'zip/zip'
require 'zip/zipfilesystem'
require 'open-uri'
class PhotoZipper
#queue = :photozip_queue
#I pass
def self.perform(id_of_object_with_images, id_of_user_to_be_notified)
user_mail = User.where(:id => id_of_user_to_be_notified).pluck(:email)
export = PhotoZipper.generate_zip(id_of_object_with_images, id_of_user_to_be_notified)
Notifications.zip_ready(export.archive_url, user_mail).deliver
end
# Zipfile generator
def self.generate_zip(id_of_object_with_images, id_of_user_to_be_notified)
object = ObjectWithImages.find(id_of_object_with_images)
photos = object.images
# base temp dir
temp_dir = Dir.mktmpdir
# path for zip we are about to create, I find that ruby zip needs to write to a real file
# This assumes the ObjectWithImages object has an attribute title which is a string.
zip_path = File.join(temp_dir, "#{object.title}_#{Date.today.to_s}.zip")
Zip::ZipOutputStream.open(zip_path) do |zos|
photos.each do |photo|
path = photo.photo.path
zos.put_next_entry(path)
zos.write photo.photo.file.read
end
end
#Find the user that made the request
user = User.find(id_of_user_to_be_notified)
#Create an export object associated to the user
export = user.exports.build
#Associate the created zip to the export
export.archive = File.open(zip_path)
#Upload the archive
export.save!
#return the export object
export
ensure
# clean up the tempdir now!
FileUtils.rm_rf temp_dir if temp_dir
end
end
app/controllers/photos_controller.rb:
format.zip do
#pick the last ObjectWithImages.. ofcourse you should include your own logic here
id_of_object_with_images = ObjectWithImages.last.id
#enqueue the Photozipper task
Resque.enqueue(PhotoZipper, id_of_object_with_images, current_user.id)
#don't keep the user waiting and flash a message with information about what's happening behind the scenes
redirect_to some_path, :notice => "Your zip is being created, you will receive an e-mail once this process is complete"
end
Many thanks to #ffoeg for helping me out. If your zips are smaller you could try #ffoeg's solution.

Answer 2

Here is my take. There could be typos but I think this is the gist of it :)
# action method, stream the zip
def download_photos_as_zip # silly name but you get the idea
generate_zip do |zipname, zip_path|
File.open(zip_path, 'rb') do |zf|
# you may need to set these to get the file to stream (if you care about that)
# self.last_modified
# self.etag
# self.response.headers['Content-Length']
self.response.headers['Content-Type'] = "application/zip"
self.response.headers['Content-Disposition'] = "attachment; filename=#{zipname}"
self.response.body = Enumerator.new do |out| # Enumerator is ruby 1.9
while !zf.eof? do
out << zf.read(4096)
end
end
end
end
end
# Zipfile generator
def generate_zip(&block)
photos = Photo.all
# base temp dir
temp_dir = Dir.mktempdir
# path for zip we are about to create, I find that ruby zip needs to write to a real file
zip_path = File.join(temp_dir, 'export.zip')
Zip::ZipFile::open(zip_path, true) do |zipfile|
photos.each do |photo|
zipfile.get_output_stream(photo.photo.identifier) do |io|
io.write photo.photo.file.read
end
end
end
# yield the zipfile to the action
block.call 'export.zip', zip_path
ensure
# clean up the tempdir now!
FileUtils.rm_rf temp_dir if temp_dir
end