Amazon::Ecs response caching to memcached

amazon_ecs_with_memcache.rb

# -*- coding: utf-8 -*-

require 'amazon/ecs'
require 'dalli'
require 'active_support/core_ext'

module Amazon
  class Ecs
    class << self
      def send_request_with_memcache(opts)
        opts = options.merge(opts) if options
        
        begin
          if content = get_content_from_memcache(opts)
            response = Response.new(content)
          else
            response = send_request_without_memcache(opts)
            dalli_client.set(memcache_key(opts), response.doc.to_xml)
          end
        rescue Dalli::RingError
          # nocache silently
        end

        response
      end
      alias_method_chain :send_request, :memcache

      def dalli_client
        @dc ||= Dalli::Client.new('localhost:11211')
      end

      def get_content_from_memcache(opts)
        if %w{ItemSearch ItemLookup SimilarLookup}.include? opts[:operation]
          dalli_client.get(memcache_key(opts))
        else
          nil
        end
      end

      def memcache_key(opts)
        o = opts.dup
        ignore_options_key_for_memcache.each do |key|
          o.delete(key)
        end

        CGI.escape(o.sort.join('-').gsub(/\s/, '%2F'))
      end

      # to keep memcache key short
      def ignore_options_key_for_memcache
        [:service, :version, :AWS_access_key_id, :AWS_secret_key, :associate_tag]
      end
    end
  end
end

amazon_ecs_with_memcache_spec.rb

# -*- coding: utf-8 -*-

require 'amazon_ecs_with_memcache.rb'

describe "Amazon::Ecs" do
  describe "send_request_with_memcache" do
    let(:request_opts) do
      Amazon::Ecs.options.merge({:Title => 'Rails', :search_index => 'Books', :operation => 'ItemSearch'})
    end
    let(:dc) { Dalli::Client.new('localhost:11211') }

    before do
      dc.delete(Amazon::Ecs.memcache_key(request_opts))
      @res = Amazon::Ecs.item_search('Rails', :type => 'Title', :search_index => 'Books')
    end

    describe "request" do
      subject {@res}
      it { should be_is_valid_request }
      its(:error) { should be_nil }
      its(:items) { should have(10).items }
    end

    describe "memcache" do
      subject {dc.get(Amazon::Ecs.memcache_key(request_opts))}
      it { should_not == nil }
    end
  end
end