A module to invalidate cache on Amazon CloudFront

cloud_front.rb

require 'openssl'
require 'net/http'
require 'net/https'

module CloudFront
  extend self

  def invalidate(path)
    date   = Time.now.utc
    date   = date.strftime("%a, %d %b %Y %H:%M:%S %Z")
    digest = OpenSSL::HMAC.digest("sha1", s3_secret_key, date)

    # 2010-11-01 is the API version
    uri = URI.parse('https://cloudfront.amazonaws.com/2010-11-01/distribution/' + distribution_id + '/invalidation')
    req = Net::HTTP::Post.new(uri.path)
    req.initialize_http_header 'x-amz-date'    => date,
                               'Content-Type'  => 'text/xml',
                               'Authorization' => "AWS %s:%s" % [s3_access_key, Base64.encode64(digest)]

    req.body = "<InvalidationBatch>" + "<Path>#{path}</Path>" + "<CallerReference>ref_#{Time.now.utc.to_i}</CallerReference></InvalidationBatch>"

    http             = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl     = true
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE
    res              = http.request(req)
    
    # res.code == 201 # 201 for successful response
    res.body
  end

  private

  def s3_access_key
    s3_config[Rails.env]['access_key_id']
  end

  def s3_secret_key
    s3_config[Rails.env]['secret_access_key']
  end

  def distribution_id
    s3_config[Rails.env]['cloud_front_distribution_id']
  end

  def s3_config
    @s3_config ||= YAML.load(File.read('config/amazon_s3.yml'))
  end
end