Paperclip, S3, and European Buckets

UPDATE @englandpost points out that newer versions of paperclip support the :s3_host_name option, see http://rubydoc.info/gems/paperclip/Paperclip/Storage/S3. Thanks @englandpost

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So you have your European S3 bucket thinking how cool you can select buckets near where your customers live, you gem install paperclip aws_s3 and do the dances and the rails and the rituals and the cap production deploy, and you get

The bucket you are attempting to access must be addressed using the specified endpoint. Please send all future requests to this endpoint.

Not Fair!

The interblags reccomend you use gem install s3 instead, with appropriate monkeypatches for Paperclip::Storage::S3, but you might end up with this:

The request signature we calculated does not match the signature you provided. Check your key and signing method.

I tried and I tried, honest, s3 just wouldn't play the signature game by amazon's rules ... couldn't get anything to work, until I stumbled on http://www.mail-archive.com/heroku@googlegroups.com/msg05407.html in which the great and goodly Dan Croak recommends you put this in config/environment.rb:

AWS::S3::DEFAULT_HOST = "s3-eu-west-1.amazonaws.com"

Well lo and behold I was finally able to upload stuff, my pretty pictures are showing up in my AWS console.

But you're not done yet: you still need to generate the correct URL (my_model.my_attachment.url) for your pictures and mp3s and videos and Large Objects and whatever your pushing up to the clouds there ... Paperclip::Storage::S3 kindly hard-codes "s3.amazonaws.com" for you, and it doesn't work.

Here's the fix:

# in config/initializers/something.rb
Paperclip.interpolates(:s3_eu_url) { |attachment, style|
  "#{attachment.s3_protocol}://s3-eu-west-1.amazonaws.com/#{attachment.bucket_name}/#{attachment.path(style).gsub(%r{^/}, "")}"
}

# in your model
has_attached_file :image, 
  :storage => :s3,
  :s3_credentials => "#{Rails.root}/config/s3.yml",
  :path => "for/example/:id/:style.:extension",
  :url  => ":s3_eu_url"

This is a big song and dance to simply tell paperclip how to construct the s3 url. Left to itself, paperclip will replace your url setting with one of its own (":s3_path_url") if it doesn't match /^:s3.*url$/. Hence, the interpolation above is called "s3_eu_url", you can write your own for singapore or whatever far-flung place you've dumped your bucket.