web 应用中常用的各种 cache详解

class ArticlesController
 def show
  @article = Article.find(params[:id])
  fresh_when :last_modified => @article.updated_at.utc, :etag => @article
 end
end

  fresh_when :etag => [@article.cache_key, current_user.id]
  fresh_when :etag => [@article.cache_key, current_user_favorited]

  //ngx_http_clear_etag(r); 

  config.middleware.use Rack::Deflater

curl -v http://localhost:3000/articles/1
< Etag: "bf328447bcb2b8706193a50962035619"
< X-Runtime: 0.286958
curl -v http://localhost:3000/articles/1 --header 'If-None-Match: "bf328447bcb2b8706193a50962035619"'
< X-Runtime: 0.293798
用fresh_when：

 
curl -v http://localhost:3000/articles/1 --header 'If-None-Match: "bf328447bcb2b8706193a50962035619"'
< X-Runtime: 0.033884

class CategoriesController < ActionController::Base
 after_filter :generate_static_file, :only => [:index]

 def index
  @categories = Category.all
 end

 def generate_static_file
  File.open(Rails.root.join('public', 'categories'), 'w') do |f|
   f.write response.body
  end
 end
end

class Category < ActiveRecord::Base
 after_save :delete_static_file
 after_destroy :delete_static_file

 def delete_static_file
  File.delete Rails.root.join('public', 'categories')
 end
end

class CategoriesController < ActionController::Base
 caches_page :index

 def update
  #...
  expire_page action: 'index'
 end
end

 upstream redis {
  server redis_server_ip:6379;
 }

 upstream ruby_backend {
  server unicorn_server_ip1 fail_timeout=0;
  server unicorn_server_ip2 fail_timeout=0;
 }

 location /categories {
  set $redis_key $uri;
  default_type  text/html;
  redis_pass redis;
  error_page 404 = @httpapp;
 }

 location @httpapp {
  proxy_pass http://ruby_backend;
 }

 redis_cache.set('categories', response.body)
 redis_cache.del('categories')

 redis_cache.setex('categories', 3.hours.to_i, response.body)

class CategoriesController
 caches_action :index, :expires_in => 1.day, :cache_path => proc {"categories/index/#{params[:page].to_i}"}
end

class ArticlesController
 caches_action :index, :expires_in => 8.hours, :if => proc {request.format.rss?}
end

class HomeController
 caches_action :index, :expires_in => 3.hours, :if => proc {!user_signed_in?}
end

- if advert = Advert.where(:name => request.controller_name + request.action_name, :enable => true).first
 div.ad
  = advert.content

- cache "adverts/#{request.controller_name}/#{request.action_name}", :expires_in => 1.day do
 - if advert = Advert.where(:name => request.controller_name + request.action_name, :enable => true).first
  div.ad
   = advert.content

- cache "articles/#{@article.id}/#{@article.updated_at.to_i}" do
 div.article
  = @article.content.markdown2html

- cache "trips/show/seo/#{@trip.fragment_cache_key}", :expires_in => 1.day do
 title #{trip_name @trip}
 meta name="description" content="..."
 meta name="keywords" content="..."

body
 div
  ...
- cache "trips/show/viewer/#{@trip.fragment_cache_key}", :expires_in => 1.day do
 - @trip.eager_load_all

 def eager_load_all
  ActiveRecord::Associations::Preloader.new([self], {:trip_days => [:weather_station_data, :nodes => [:entry, :notes => [:photo, :video, :audio]]]}).run
 end

 def cache_if (condition, name = {}, cache_options = {}, &block)
  if condition
   cache(name, cache_options, &block)
  else
   yield
  end
 end

- cache_if !user_signed_in?, "xxx", :expires_in => 1.day do

class Article
 has_many :comments
end

class Comment
 belongs_to :article, :touch => true
end

# controller
 def index
  @articles = Article.first(10)
 end

# view
- @articles.each do |article|
 h1 = article.name
 span = article.category.name

SELECT `categories`.* FROM `categories` WHERE `categories`.`id` = ?

 def index
  @articles = Article.includes(:category).first(10)
 end

SELECT `categories`.* FROM `categories` WHERE `categories`.`id` in (?,?,?...)

class User < ActiveRecord::Base
 include IdentityCache
end

class Article < ActiveRecord::Base
 include IdentityCache
 cached_belongs_to :user
end

# 都会命中缓存

User.fetch(1)
Article.find(2).user

class User < ActiveRecord::Base
 acts_as_cached(:version => 1, :expires_in => 1.week)
end