Heroku and carrierwave don't load my s3 configuration

I have an application on Heroku that uses the Carrierwave gem to upload images to S3.

I have set the s3 configuration in an initializer called carrierwave.rb

CarrierWave.configure do |config|
  config.s3_access_key_id = 'XXXXXXXXXXXXXXXXXXXX'
  config.s3_secret_access_key = 'XXXXXXXXXXXXXXXXX'
  config.s3_bucket = 'XXXXX'
  config.storage = :s3
end

This works fine in development on my local machine, however once I deploy t开发者_运维百科o Heroku I get the following error

A Errno::EACCES occurred in events#update:

Permission denied - /app/public/uploads
/usr/ruby1.8.7/lib/ruby/1.8/fileutils.rb:243:in `mkdir'

Obviously it's trying to write to the heroku server which is read only and not picking up my s3 settings.

Does anyone know how I can get heroku to send my files to s3?

From CarrierWave wikki:

Heroku has a read-only filesystem, so uploads must be stored on S3 and cannot be cached in the public directory.

You can work around this by setting the cache_dir in your Uploader classes to the tmp directory:

Check out https://github.com/jnicklas/carrierwave/wiki and scroll to the bottom section labeled "CarrierWave on Heroku" to see how they set this up. Hope this helps someone.

Have you looked at this demo app.

In particular the uploaded class here