This document discusses caching techniques in Rails, including page caching, action caching, and fragment caching. Page caching stores entire static HTML pages to serve cached content quickly without running Rails. Action caching runs controllers but caches output. Fragment caching caches portions of views. Caches can be expired based on model changes or timed expiration. Plugins like cache_fu and sweeper generators help manage caching.

1. Rails Cache
级别：基础
徐祥军
martin@recity.net
http://www.recity.net

2. About ReCity
ReCity -- 城市信息分享平台
• 所有信息均来自于用户
• 用户创建、拥有、维护和分享
• 创新机制使得信息能自动趋于准确、及时、
有效
• 不仅仅分享信息，还分享收益
Shanghai On Rails 2007

3. Rails Cache
• Page Cache
• Action Cache
• Fragment Cache
Shanghai On Rails 2007

4. Use Cache
config.action_controller.perform_caching = true
Shanghai On Rails 2007

5. Page Cache
• Rails 内速度最快的一种缓存
• 简单，容易使用
• Cached Page,不必再执行Rails,直接由Web Server
加载静态的Html页面
Shanghai On Rails 2007

6. Page Cache Example
class UsersController < ApplicationController
caches_page :show
def show
…
end
…
end
Shanghai On Rails 2007

7. http://localhost/users/show/100
Rendering users/show
Cached page: /users/show/100.html
$ ls public/users/show
100.html
Shanghai On Rails 2007

8. Page Cache Sweeper
class UserSweeper < ActionController::Caching::Sweeper
observe User
def after_update(record)
expire_page :controller=>:users,:action=>:show,:id=>record.id
end
…
end
class UsersController < ApplicationController
cache_sweeper :user_sweeper
caches_page :show
Shanghai On Rails 2007

9. User.find(100).update_attribute :login,’something’
Expired page: /users/show/100.html (0.00000)
Shanghai On Rails 2007

10. Page Cache Problems
• Page Cache的内容是静态的html，是完全public，所有用
户看到完全一样的页面，如何处理极少量的不一致或个性
化的内容或有有权限验证的内容
1. Ajax
2. Client Javascript
3. 放弃，改用Action Cache或其他Cache
Shanghai On Rails 2007

11. Page Cache Problems
• Page Caches生成的文件名是通过url_for生成的，参数不
会被保存
分页?page=1
复杂?sort=score&user_id=100&category_id=1
1：将参数配置到routes里面去，
/users/list/page
2：放弃，采用其他的cache
Shanghai On Rails 2007

12. Action Cache
• 类似Page Cache
• Action Cache 执行
调用controller
1.
执行before_filter
2.
检测cache是否存在，如果存在则返回cache
3.
• 要比Page Cache慢，但是也够快
• 底层调用的Fragment Cache
Shanghai On Rails 2007

13. Action Cache Example
类似于Page Cache：caches_action，expire_action
class UsersController < ApplicationController
before_filter :authenticate
caches_page :show
cache_sweeper :user_sweeper
def show
…
end
end
Shanghai On Rails 2007

14. http://localhost/users/show/100
Rendering users/show
Cached fragment: localhost/users/show/100 (0.00000)
$ ls -al tmp/cache/localhost/users/show/*
… tmp/cache/localhost/users/show/100.cache
Fragment read: localhost/users/show/100 (0.00000)
Shanghai On Rails 2007

15. expire_action :controller=>:users,:action=>:show,:id=>record.id
Shanghai On Rails 2007

16. Action Cache Problem
• 查询字符
caches_action_with_params
expire_action_with_params
Shanghai On Rails 2007

17. Fragment Cache
• 用于cache 视图中代码块
• 默认会在/tmp/cache目录下生成.cache文件
• 清除缓存 expire_fragment
Shanghai On Rails 2007

18. Fragment Cache Example
<%cache do%>
<ul>
<%@users.each do |user|%>
<li><%=link_to user.login,user_path(user)%></li>
<%end%>
</ul>
<%end%>
Shanghai On Rails 2007

19. 但是还是执行了查询？
unless read_fragment()
@users = User.paginate :all, :page=>params[:page]||1
end
Shanghai On Rails 2007

20. Fragment Cache
• 自定义片段的名称
页面中的fragment cache多于一个时，需指定额外名称
类似url_for
cache(:action=>’show’,:part=>’users’)
cache(:action=>’show’,:part=>’users’,:page=>1 [,…])
localhost/users/show?page=1
localhost/users/show?page=1&part=users
expire_fragment [params…]
Shanghai On Rails 2007

21. Action/Fragment Cache 存储方式
内存
•
文件
•
• DRB
• MemCached
Shanghai On Rails 2007

22. Expiring Strategy
• Model状态
• 时间
• Others
Shanghai On Rails 2007

23. Useful Plugins
• sweeper generator
• timed_fragment_cache
• cache_fu
• cached_model
Shanghai On Rails 2007

24. sweeper generator
./script/generate sweeper SweeperName callback1 callback2
Shanghai On Rails 2007

25. timed_fragment_cache
• View
<% cache 'fragment_name', 10.minutes.from_now do %>
#the cached fragment which does something intensive
<% end %>
• Controller
when_fragment_expired 'fragment_name', 10.minutes_from_now do
#some intensive code
end
Shanghai On Rails 2007

26. cache_fu
class User < ActiveRecord::Base
acts_as_cached
end
Shanghai On Rails 2007

27. CachedModel
class User < CachedModel
end
Shanghai On Rails 2007

28. More
• Mode Cache
• Query Cache(Edge Rails)
Shanghai On Rails 2007

29. Questions?
Martin@Recity.Net
Shanghai On Rails 2007