Question

我的Rails 3应用程序生成的页面将在指定的时间段内发生变化，然后在其余生中保持静态（无变化）（想想：体育记分牌）

这似乎是完整页面缓存的绝佳机会，因此我选择了Rack :: Cache，使用响应的Last-Modified部分来指示缓存何时无效。

缓存效果很好 - 太好了。即使使用晚于请求的If-Modified-Since字段的日期/时间更新Last-Modified字段并且响应生成状态200（而不是304），浏览器仍然会加载在服务器上缓存的页面版本。

以下是我在服务器调试日志中看到的内容：

App 16638 stdout: Started GET "/games/2014/2/10" for xx.xx.xx.xxx at 2014-02-11 04:04:11 +0000
App 16638 stdout: Processing by GamesController#index as HTML
App 16638 stdout:   Parameters: {"year"=>"2014", "month"=>"2", "day"=>"10"}
App 16638 stdout:   Game Load (2.8ms)  SELECT "games".* FROM "games" WHERE "games"."date" = '2014-02-10'
App 16638 stdout:   Game Load (2.8ms)  SELECT "games".* FROM "games" WHERE "games"."id" = 877 LIMIT 1
App 16638 stdout:   Team Load (1.3ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 10 LIMIT 1
App 16638 stdout:   Team Load (0.7ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 23 LIMIT 1
App 16638 stdout:   Game Load (4.2ms)  SELECT "games".* FROM "games" WHERE "games"."id" = 875 LIMIT 1
App 16638 stdout:   Team Load (0.6ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 17 LIMIT 1
App 16638 stdout:   Team Load (5.4ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 2 LIMIT 1
App 16638 stdout:   Game Load (7.0ms)  SELECT "games".* FROM "games" WHERE "games"."id" = 874 LIMIT 1
App 16638 stdout:   Team Load (0.7ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 9 LIMIT 1
App 16638 stdout:   Team Load (7.9ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 27 LIMIT 1
App 16638 stdout:   Game Load (0.7ms)  SELECT "games".* FROM "games" WHERE "games"."id" = 876 LIMIT 1
App 16638 stdout:   Team Load (0.4ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 18 LIMIT 1
App 16638 stdout:   Team Load (0.4ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 11 LIMIT 1
App 16638 stdout:   Game Load (0.6ms)  SELECT "games".* FROM "games" WHERE "games"."id" = 873 LIMIT 1
App 16638 stdout:   Team Load (4.0ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 12 LIMIT 1
App 16638 stdout:   Team Load (0.6ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 8 LIMIT 1
App 16638 stdout:   Game Load (5.4ms)  SELECT "games".* FROM "games" WHERE "games"."id" = 872 LIMIT 1
App 16638 stdout:   Team Load (0.6ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 28 LIMIT 1
App 16638 stdout:   Team Load (3.9ms)  SELECT "teams".* FROM "teams" WHERE "teams"."id" = 19 LIMIT 1
App 16638 stdout: Latest game: 2014-02-11 03:44:50 UTC
App 16638 stdout: Cache read: views/xxxx/games/2014/2/10
App 16638 stdout: Dalli::Server#connect 127.0.0.1:11211
App 16638 stdout: Read fragment views/xxxxx/games/2014/2/10 2.6ms
App 16638 stdout: Completed 200 OK in 618.2ms (ActiveRecord: 128.8ms)
App 15100 stderr: cache: [GET /games/2014/2/10] stale, invalid, store
App 16638 stdout: Started GET "/assets/bootstrap.css" for 66.55.150.181 at 2014-02-11 04:04:12 +0000
App 16638 stdout: Served asset /bootstrap.css - 304 Not Modified (12ms)
App 15100 stderr: cache: [GET /assets/bootstrap.css] stale, valid, store
App 15100 stderr: cache: [GET /assets/application-85cd667c6ae785b5d80f452fe6ad811e.js] fresh
App 15100 stderr: cache: [GET /assets/application-50dd9f33494a58a079e7417a68763e42.css] fresh

以下是一个示例请求/响应（请参阅200状态）：

    Request URL:http://xxxxxxx.com/games/2014/2/10
Request Method:GET
Status Code:200 OK
Request Headersview source
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Charset:ISO-8859-1,utf-8;q=0.7,*;q=0.3
Accept-Encoding:gzip,deflate,sdch
Accept-Language:en-US,en;q=0.8
Cache-Control:max-age=0
Connection:keep-alive
Cookie:_gamestory_app_session=BAh7B0kiD3Nlc3Npb25faWQGOgZFVEkiJWIwYjAwNWQ3NTBmYTk4YjQ0YWRjYjEwMWQ5Y2ZjYTA2BjsAVEkiEF9jcx3JmX3Rva2VuBjsARkkiMXdKNWZZUWFhZDVHN3hEeEJjaWxYclp1NmN4OGUrSkI4VzJ2eXdWOUsrc1E9BjsARg%3D%3D--6f99b71bca632560c069c371fdb6a4477a26dfa3
Host:xxxxxxxxx.com
If-Modified-Since:Tue, 11 Feb 2014 03:43:06 GMT
If-None-Match:"e282d8be52fbe437d3c2d3908288100d"
User-Agent:Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.56 Safari/537.17
Response Headersview source
Age:0
Cache-Control:public
Connection:keep-alive
Content-Length:10411
Content-Type:text/html; charset=utf-8
Date:Tue, 11 Feb 2014 04:04:11 GMT

ETag:"d6d4c1f573a56353e0abbe14de76e306"
Last-Modified:Tue, 11 Feb 2014 03:44:50 GMT
Server:nginx/1.4.4 + Phusion Passenger 4.0.29
Status:200 OK
X-Content-Digest:7b2caeed19cc4674669f4c386271054427342b5e
X-Powered-By:Phusion Passenger 4.0.29
X-Rack-Cache:stale, invalid, store
X-Request-Id:c19584efff9941bf5c456cb68d85b192
X-Runtime:0.661659
X-UA-Compatible:IE=Edge,chrome=1

在相关的控制器中，我对给定的操作使用了before_filter，在该过滤器中，我在页面上最后更新的对象上使用了fresh_when。这似乎在响应中生成了正确的日期/时间，但我包含了任何可能错误的代码（为了简洁，我删除了show动作）：

class GamesController < ApplicationController
  helper ApplicationHelper
  before_filter :set_index_cache_headers, :only => [:index]
  caches_action :index

  def set_index_cache_headers
    @date = Date.today

    if params[:year] && params[:month] && params[:day]
      @date = Date.new(params[:year].to_i, params[:month].to_i, params[:day].to_i)
    else
      most_recent_game = Game.where(status: [:final, :in_progress]).order("date DESC").first

      if most_recent_game != nil
        @date = most_recent_game.date
      end
    end

    @games = Game.where(:date => @date).compact

    @game_infos = []

    @games.each do |g|
      @game_infos.push GameInfo.new(g.id)
    end

    @latest_game = @games.max_by{|g| g.updated_at}

    Rails.logger.debug "Latest game: #{@latest_game.updated_at}"
    fresh_when(@latest_game, public: true)
  end

  def index

  end
end

Answer 1

如果我理解你的尝试，我相信你需要设置expires_in（最好是在after_filter中，这样你就不会缓存500状态的响应）。现在，看起来机架缓存无限期地缓存您的页面（或者无论默认值是什么），并且您的请求永远不会触及rails后端。 Rack-cache认为您的缓存是“新鲜的”，因此不会回过头来重新生成页面。本文对其工作原理给出了很好的解释：

http://blog.tonycode.com/archives/418

仅当您实际通过机架缓存中间件和rails层时，才会调用“fresh_when”。如果这样做，除非您更新了记录（@latest_game），否则它将返回304。

希望有所帮助，祝你好运！缓存失效是一种痛苦。

Answer 2

事实证明，控制器中的这一行：

caches_action :index

是罪魁祸首。我的意图是只使用Rack :: Cache HTTP缓存，但是这一行激活了Rails动作缓存，这不是我的意图。让两个缓存系统一起运行是导致问题的原因。删除此行已解决问题。

使用Rails + Rack :: Cache的HTTP缓存无效

2 个答案: