Heroku file upload problem

Question

I've been having a problem uploading a CSV file to Heroku and processing it. It works fine in my local environment. Just do be clear, I don't need to save the file on Heroku, just access it during the request in order to convert it into a string for processing and importing into the DB.

What I want to do is:

1. Upload CSV file
2. Strip out the header block, depending on which network the report is from
3. Read the CSV data into the DB. This step works fine.

Controller code:

  def create
    @account = Account.find(params[:report][:account_id])
    @file = params[:report][:file].read
    # logger.info file.inspect
    case @account.provider
    when "Microsoft AdCenter" then @file.gsub!(/\A(.*)\n\n/im, "")
    when "Google AdWords" then @file.gsub!(/\A(.*)\n/i, "")
    else
      raise "Invalid PPC report format"
    end
  end

Here's the stack trace:

Processing ImportController#create (for XX.182.6.XXX at 2010-09-11 09:19:01) [POST]
  Parameters: {"commit"=>"Upload", "action"=>"create", "authenticity_token"=>"XXXXXwoFpvRO3vN8XVXRDg8rikFsj2TFTW7mrcTgg=", "controller"=>"import", "report"=>{"account_id"=>"1", "file"=>#<File:/home/slugs/126077_0657264_9a92/mnt/tmp/RackMultipart.9845.0>}}

NoMethodError (private method `gsub!' called for #<Tempfile:0x2b8ccb63ece0>):
  /usr/local/lib/ruby/1.8/delegate.rb:270:in `method_missing'
  app/controllers/import_controller.rb:15:in `create'
  warden (0.10.7) lib/warden/manager.rb:35:in `call'
  warden (0.10.7) lib/warden/manager.rb:34:in `catch'
  warden (0.10.7) lib/warden/manager.rb:34:in `call'
  /home/heroku_rack/lib/static_assets.rb:9:in `call'
  /home/heroku_rack/lib/last_access.rb:25:in `call'
  /home/heroku_rack/lib/date_header.rb:14:in `call'
  thin (1.0.1) lib/thin/connection.rb:80:in `pre_process'
  thin (1.0.1) lib/thin/connection.rb:78:in `catch'
  thin (1.0.1) lib/thin/connection.rb:78:in `pre_process'
  thin (1.0.1) lib/thin/connection.rb:57:in `process'
  thin (1.0.1) lib/thin/connection.rb:42:in `receive_data'
  eventmachine (0.12.6) lib/eventmachine.rb:240:in `run_machine'
  eventmachine (0.12.6) lib/eventmachine.rb:240:in `run'
  thin (1.0.1) lib/thin/backends/base.rb:57:in `start'
  thin (1.0.1) lib/thin/server.rb:150:in `start'
  thin (1.0.1) lib/thin/controllers/controller.rb:80:in `start'
  thin (1.0.1) lib/thin/runner.rb:173:in `send'
  thin (1.0.1) lib/thin/runner.rb:173:in `run_command'
  thin (1.0.1) lib/thin/runner.rb:139:in `run!'
  thin (1.0.1) bin/thin:6
  /usr/local/bin/thin:20:in `load'
  /usr/local/bin/thin:20

Rendering /disk1/home/slugs/126077_0657264_9a92/mnt/public/500.html (500 Internal Server Error)

Anyone know why it works just fine locally but then produces that error on Heroku?

Thanks!

Answer 1

Are you aware of this?

http://docs.heroku.com/constraints

Answer 2

Yep. the file system is read-only. You can store your files on S3.

Answer 3

Not entirely true, actually. It turns out that if you upload a file to Heroku, you can access it for the duration of the session via the Tempfile class. I was able to read the tempfile into a string and then process it as needed (it's a CSV):

@file = IO.read(params[:report][:file].path)

Works fine for text/csv files, but I guess if you want to do more than basic text manipulation you have to go with S3 as Joost suggests.