I’ve been struggling a bit with some problems uploading files with attachment_fu recently. I’m going to go through the common problems I’ve had. Attachment_fu is the best thing I’ve seen out there for upload handling. And, hopefully mentioning these gotchas will save some people some time.

1) Mongrel’s Dying with S3

This is really a problem with the AWS-S3 library. The problem is that the library uses persistent connections by default, and the last thing that Mongrel wants to deal with is keeping a persistent connection open to an outside service while its trying to serve unrelated web requests. My current theory is that the multi-threading + Mutex means that the persistent connection is ignored and times out, then when the app comes back to try and say hi to the connection, it just waits forever. This is totally unproven, but its the theory I’ve got in my brain.

Luckily, this is easy to fix! Just add this to your config/amazon_s3.yml

development:
  bucket_name: mybucket_develompent
  access_key_id: 1RX1190JQBAV
  secret_access_key: RN2nBEFhYu8k5S3kVXtM
  persistent: false

Obviously, do that with all three types of connections. Dead mongrels, no more! But, we aren’t done with S3….

2) EofError with S3

This generally happens when you have thumbnails. Why does it happen? Because it takes too long for Rails to have multiple POST conversations with S3 and something weird happens with the connections. Yes, even if you turn off persistent connections. This is usually ok for single-file uploads to S3… aka, no thumbnails. It is really unfortunate that we can’t use Thread.new in Rails with any consistency because doing the uploads to S3 after the request is finished would be really fantastic and would nip this problem in the butt.

The only known solution is to switch to file_system. That, or use Merb which is thread safe.

3) Good Attachments Validate as not having a Size

I’m still a bit unclear about what is going on with this one. It seems to be inconsistent and mostly has to do with if the upload object given by the OS is a StringIO or a TempFile. The way to tell this one apart from #4 is that when you use debugger… the #size attribute isn’t set at all. You’ll get a “Size is not included in the list” with a #save! .

Add this line to your attachment_fu.rb file in the plugin…

def uploaded_data=(file_data)
  return nil if file_data.nil? || file_data.size == 0
  self.size = file_data.size # <----- THIS LINE 
  self.content_type = file_data.content_type
  self.filename     = file_data.original_filename if respond_to?(:filename)
  if file_data.is_a?(StringIO)
    file_data.rewind
    self.temp_data = file_data.read
  else
    self.temp_path = file_data.path
  end
end

That should solve that!

4) Larger files FAIL!

Ok, this one is a gotcha and not at all a bug. In fact, I’m kind of embarrassed that I ever had this problem. Let’s say you have a general file upload area. Not just images… you want attachments put onto something on your site. And let’s also assume that this is a protected section. So, you build your attachment_fu things to look like this.

has_attachment :storage => :file_system

And that’s all you do because you don’t care about type, size, etc. GOTCHA! You may not have specified a max_size, but attachment_fu did! It sets the default max_size to 1.megabyte. DOH! So, the error you get is the same one as above… “Size is not included in the list” That error message could be a touch more useful, IMHO. However, this is also an easy fix…

has_attachment :storage => :file_system,
                   :max_size => 100.megabytes  # Since this is admin, and we don't care

So, there you go. Hopefully these helped some of you out there who have been using this non-released software. I guess that’s what we get for living on the dangerous side!