铁轨上的表演

Question

我对导轨的性能有疑问。当我像这样对控制器进行 ajax 调用时：

def test
    @hotels = Hotel.all
    render :json => ['hotels' => @hotels ], :include=> [:country, :city]
end

完成可能需要 2-5 秒。我的数据库中只有 40 家酒店。我认为它很长......例如，Django上的相同请求将需要400ms

我是不是忘了配置好我的环境？

我使用 Rails 企业版和乘客版。

编辑：我的日志文件：

     Started GET "/hotels/test.json" for 172.16.81.1 at Wed Oct 12 22:11:06 +0200 2011
    [paperclip] Duplicate URL for image with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in HotelImage class
    [paperclip] Duplicate URL for thumbnail with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in Hotel class
    [paperclip] Duplicate URL for map with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in Hotel class
    [paperclip] Duplicate URL for thumbnail with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in DestinationAlbumPhoto class
    [paperclip] Duplicate URL for map with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in Destination class
    [paperclip] Duplicate URL for image with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in Continent class
    [paperclip] Duplicate URL for thumbnail with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in Destination class
    [paperclip] Duplicate URL for image with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in Event class
    [paperclip] Duplicate URL for thumbnail with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in HotelAlbumPhoto class
    [paperclip] Duplicate URL for map with /system/:attachment/:id/:style/:filename. This will clash with attachment defined in Event class
      Processing by HotelController#test as JSON
      [1m[36mHotel Load (0.2ms)[0m  [1mSELECT `hotels`.* FROM `hotels`[0m
      [1m[35mCountry Load (0.1ms)[0m  SELECT `countries`.* FROM `countries` WHERE (`countries`.`id` = 3)
      [1m[36mCity Load (0.1ms)[0m  [1mSELECT `cities`.* FROM `cities` WHERE (`cities`.`id` = 2)[0m
    Completed 200 OK in 405ms (Views: 366.1ms | ActiveRecord: 0.3ms)

它的写入时间为 405 毫秒，但 Firefox 告诉我 3.7 秒。

我的酒店模型：

class Hotel < ActiveRecord::Base
  cattr_reader :per_page
  @@per_page = 16

  belongs_to :hotel_type
  belongs_to :hotel_theme
  belongs_to :country
  belongs_to :city
  belongs_to :destination
  belongs_to :continent

  has_many :hotel_comments, :dependent => :destroy

  has_many :hotel_album_photos, :dependent => :destroy

  has_many :hotel_activity_values

  has_many :hotel_service_values

  accepts_nested_attributes_for :hotel_album_photos

  has_attached_file :thumbnail, :styles => { :medium => "300x300>", :thumb => "191x134>"} , :default_url => '/images/default/missing.png' 
  has_attached_file :map, :styles => { :medium => "300x300>", :thumb => "191x134>"} , :default_url => '/images/default/missing.png' 

  scope :country, lambda { |country_id|
     self.scoped.where('country_id IN ( ? )', country_id) unless country_id.blank?
  }

  scope :selection, lambda { |selection|
     self.scoped.where('selection = ? ', 1) unless selection.blank?
  }

  scope :city, lambda { |city_id|
      self.scoped.where('city_id IN ( ? )', city_id) unless city_id.blank?
  }

  scope :hoteltype, lambda { |type|
      self.scoped.where('hotel_type_id IN ( ? )', type) unless type.blank?
   }

  scope :theme, lambda { |theme|
      self.scoped.where('hotel_theme_id IN ( ? )', theme) unless theme.blank?
   }

  scope :prices, lambda { |prices|
      condition = []
      prices.each do |price|
        pricesArray = price.split('-')
        condition.push '(price BETWEEN ' + pricesArray[0] + ' AND ' + pricesArray[1] + ')'
      end
      self.scoped.where(condition.join(' OR ')) 
   }

   scope :order_by_price, lambda { |direction|
     self.scoped.order('price ' + direction)
   }

   scope :order_by_rate, lambda { |rate|
     self.scoped.order('global_rate ' + rate)
   }

   scope :services, lambda { |services|
      {:joins => [:hotel_service_values ]  , :conditions => { :hotel_service_values => {:hotel_service_id  => services}}}
   }

  scope :limiter, lambda { |limiter|
      self.scoped.limit(limiter)
   }

end

感谢您的帮助。

Answer 1

我正在使用 VMWare 使我的 Web 服务器运行。我的表演问题与此有关。我在这里找到我的解决方案：

Webrick is very slow to respond. How to speed it up?

Answer 2

查看日志，Rails 似乎认为它在 405 毫秒内得到了响应。这让堆栈的其余部分需要考虑：

1. 导轨 (✓)
2. 乘客
3. 阿帕奇
4. 网络
5. DNS 解析
6. 浏览器渲染

首先，看看其他浏览器的表现如何。我在我们的一个（非 Rails）网站上看到偶尔出现问题，使用 Firefox，而基于 Webkit 的浏览器（Safari、Chrome）还可以。也许 Firefox 出于某种原因（例如 DNS resolving issues 或其他）阻塞了。

如果所有浏览器都相同（或者特别是如果 Firefox 是罪魁祸首），那么打开 Firebug 并查看Net 标签，尤其是其下的 XHR (AJAX) 标签。将鼠标悬停在其中一个查询的时间栏上可查看时间的细分：DNS、连接、发送、等待、接收。

如果 Firebug 表明时间花在请求本身上（发送、等待、接收），那么看看 Apache 日志 - 打开 CustomLog 时间报告（添加 %D - see documentation）并查看Apache 认为这些请求需要多长时间。

这应该会缩小您的问题范围以进一步分析原因。

Answer 3

看看你的代码，我猜你有一个简单的“N+1”问题。

即您将@hotels 加载到一个数组中，但是当您来生成json 你加载country和cityfor eachhotel。

因此，对于您的 40 家酒店，您总共需要进行 81 次数据库查询。

这可以通过在加载时执行include 来改进。

老式风格

Hotel.all(:include => [:country, :city])

Rails 3 风格

Hotel.includes(:country, :city).all

通过此更改，您总共应该只进行 3 次数据库调用。

有关详细信息，请参阅 Eager Loading 上的 Rails 指南。