Amazon CloudFront cache invalidator for Paperclip & Fog for use with various defined image styles

cloud_front_invalidator.rb

require 'openssl'
require 'digest/sha1'
require 'net/https'
require 'base64'

class CloudFrontInvalidator
	#file - The Paperclip attachment
	#style - The defined style to invalidate (e.g. :original, :thumbnail...)
	def initialize(file, style = :original)
		@aws_account = aws_access_key_id
		@aws_secret = aws_secret_access_key
		@path = URI.parse(file.url(style)).path
	end

	def invalidate
		date = Time.now.strftime("%a, %d %b %Y %H:%M:%S %Z")
		digest = Base64.encode64(OpenSSL::HMAC.digest(OpenSSL::Digest::Digest.new('sha1'), @aws_secret, date)).strip
		#Bucket_ID - This is the the Amazon Cloud Front Distribution ID for your bucket
		#2010-11-01 identifies the version of the CloudFront API you use
		uri = URI.parse("https://cloudfront.amazonaws.com/2010-11-01/distribution/#{Bucket_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" % [@aws_account, digest]
		})
		#Caller_Ref - This is a unique value that you provide to Amazon Cloudfront
		req.body = %|<InvalidationBatch><Path>#{@path}</Path><CallerReference>#{Caller_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)
		return res.code == '201'
	end
end