memcached作为Rails中的Object存储

Question

我在我的Rails应用程序中使用Memcached作为Object Store,我在其中存储了memcached中User对象的搜索结果

现在,当我获取数据时,我得到了Memcached Undefined Class/Module Error.我在这个博客中找到了解决这个问题的方法

http://www.philsergi.com/2007/06/rails-memcached-undefinded-classmodule.html

 before_filter :preload_models
  def preload_models
    Model1
    Model2
  end

建议事先预装模型.我想知道是否有一个更优雅的解决方案来解决这个问题,并且使用预加载技术有任何缺点.

提前致谢

Answer 1

我也有这个问题,我想我想出了一个很好的解决方案.

您可以覆盖fetch方法并挽救错误并加载正确的常量.

module ActiveSupport
  module Cache
    class MemCacheStore
      # Fetching the entry from memcached
      # For some reason sometimes the classes are undefined
      #   First rescue: trying to constantize the class and try again.
      #   Second rescue, reload all the models
      #   Else raise the exception
      def fetch(key, options = {})
        retries = 2 
        begin
          super
        rescue ArgumentError, NameError => exc         
          if retries == 2
            if exc.message.match /undefined class\/module (.+)$/
              $1.constantize
            end
            retries -= 1
            retry          
          elsif retries == 1
            retries -= 1
            preload_models
            retry
          else 
            raise exc
          end
        end
      end

      private

      # There are errors sometimes like: undefined class module ClassName.
      # With this method we re-load every model
      def preload_models     
        #we need to reference the classes here so if coming from cache Marshal.load will find them     
        ActiveRecord::Base.connection.tables.each do |model|       
          begin       
            "#{model.classify}".constantize 
          rescue Exception       
          end     
        end       
      end
    end
  end
end

Answer 2

今天就这样,设法提出了一个应该适用于所有课程的更简洁的解决方案.

Rails.cache.instance_eval do
  def fetch(key, options = {}, rescue_and_require=true)
    super(key, options)

  rescue ArgumentError => ex
    if rescue_and_require && /^undefined class\/module (.+?)$/ =~ ex.message
      self.class.const_missing($1)
      fetch(key, options, false)
    else
      raise ex
    end
  end
end

不知道为什么[MemCacheStore]没有[MemCacheStore.const_missing]调用方法,一切都以正常的"Rails-y"方式调用.但是,这应该效仿!

干杯,

克里斯