How to keep temp files over requests in Rails?

Question

In my Rails application users can upload Excel files. In my model there is a class ImportFile that uses attachment_fu like this:

class ImportFile < ActiveRecord::Base
  has_attachment :storage => :file_system, :path_prefix => 'public/imports', :max_size => 10.megabytes
end

When user clicks "Add file" he enters a page with a <%= fields.file_field :uploaded_data %>. attachment_fu does it's job and file upload is being done (let's ommit validation problems). I want to keep this file for future so I copy uploaded file to other temp file. Temp file is working fine - I can see it on disk.

def self.write_to_tmp(data)
    temp_file = Tempfile.new("import", "#{Rails.root}/tmp")
  begin
    temp_file.write(data)
  ensure
    temp_file.close(false)
  end
  temp_file
end

What I want to do is to show user a preview and then let him choose if he wants to add a file or discard it - there are two buttons. I have a problem when user chooses to save a file, because a temp file I've just created above is gone. It is deleted before request.

Does anyone has hints how to achive this? Or can point me to upload-with-preview file scenario like the one I've presened? I've been looking for days, but I've failed to find one.

Answer 1

The most reliable approach to this sort of thing would be to create a simple "upload" tracking model like you have there, but using Paperclip instead. This can be configured to handle a very large number of files.

You need to actually save these records for them to persist between requests. This will lead to orphaned records, but a simple cron job or rake task you can kill off all the unused files any time you need to.

Creating a large number of files in a single directory is usually a bad idea. Paperclip has a path parameter which will split up your ID number into parts, so record #903132 goes into .../90/31/32 for example.

Keep a regular attachment, and if they want to discard it, delete it, otherwise use it. At some point later clean out all the unused attachments.