Rake task for copying Rails compiled assets to S3

assets_deploy.rb

require 'aws/s3'
require 'digest/md5'
require 'mime/types'

## These are some constants to keep track of my S3 credentials and 
## bucket name. Nothing fancy here.    

AWS_ACCESS_KEY_ID = ENV['S3_KEY']
AWS_SECRET_ACCESS_KEY = ENV['S3_SECRET']
AWS_BUCKET = ENV['S3_BUCKET']


## This defines the rake task `assets:deploy`. 
namespace :assets do  
  desc "Deploy all assets in public/assets to S3/Cloudfront"
  task :deploy, :env, :branch do |t, args|

## Use the `s3` gem to connect my bucket
    puts "== Uploading assets to S3/Cloudfront"
		AWS::S3::Base.establish_connection!(
    :access_key_id     => AWS_ACCESS_KEY_ID,
    :secret_access_key => AWS_SECRET_ACCESS_KEY
  	)
    service = AWS::S3::Service.new(
      :access_key_id => AWS_ACCESS_KEY_ID,
      :secret_access_key => AWS_SECRET_ACCESS_KEY)
    bucket = AWS::S3::Bucket.find(AWS_BUCKET)

## Needed to show progress
    STDOUT.sync = true

## Find all files (recursively) in ./public/assets and process them.
    Dir.glob("public/assets/*").each do |file|

## Only upload files, we're not interested in directories
      if File.file?(file)

## Slash 'public/' from the filename for use on S3
        remote_file = file.gsub("public/", "")

## Try to find the remote_file, an error is thrown when no
## such file can be found, that's okay.  
        begin
          obj = bucket[remote_file]
        rescue
          obj = nil
        end

## If the object does not exist, or if the MD5 Hash / etag of the 
## file has changed, upload it.
        if !obj || (obj.etag != Digest::MD5.hexdigest(File.read(file)))
            print "U"

## Simply create a new object, write the content and set the proper 
## mime-type. `obj.save` will upload and store the file to S3.
            AWS::S3::S3Object.store(remote_file, open(file), AWS_BUCKET)
        else
          print "."
        end
      end
    end
    STDOUT.sync = false # Done with progress output.

    puts
    puts "== Done syncing assets"
  end
end