db_cache.rb

# -*- coding: utf-8 -*-
require 'memcache_client'
require 'singleton'
class DBCache

  include Singleton

  attr_accessor :connection

  def load_config
    self.connection = MemcacheClient.new("YOUR_HOST_WITH_PORT", {
                        :timeout => 5.0,
                        :check_size => false,
                        :prefix_key => "", 
                        :prefix_delimiter => ":",
                      })
  end

  def self.platform_prefix_key
    pkey = Rails.env
    return AppResources.mixi? ? pkey : "#{AppResources[:application_platform]}_#{pkey}"
  end

  module DummyClassMethods
    def set(k, v, ttl=0, marshal=true)
    end

    def get(k, marshal=true)
    end

    def delete(k)
    end

    def server_by_key(key)
    end

    def reconnect!
      # no implementation
    end
  end

  module ClassMethods
    def set(k, v, ttl=0, marshal=true)
      # key, value, ttl=604800, marshal=true
      return self.connection.set(k, v, ttl, marshal)
    end

    def get(k, marshal=true)
      # keys, marshal=true
      return autoload_missing_constants { self.connection.get(k, marshal) }
    end

    def delete(k)
      return self.connection.delete(k)
    end

    def reconnect!
      # no implementation
    end

    def autoload_missing_constants
      begin
        yield
      rescue ArgumentError => error
        lazy_load ||= Hash.new { |hash, hash_key| hash[hash_key] = true; false }
        if error.to_s[/undefined class|referred/] && !lazy_load[error.to_s.split.last.sub(/::$/, '').constantize]
          retry
        else
          raise error
        end
      end
    end
  end

  def self.connection
    self.instance.load_config if self.instance.connection.nil?
    return self.instance.connection
  end

  def self.enabled
    return AppResources['db_cache_enabled']
  end

  if DBCache.enabled
    extend ClassMethods
  else
    extend DummyClassMethods
  end
end