思考middleware

Transcript

1. rack-middleware 是如何⼯工作的 覃明圆（盛安德武汉分公司）
2. 主要内容 • 什么是 rack-middleware - middleware 的⺫⽬目的 - middleware 单个实现 - middleware 如何协同⼯工作 • rack-middleware 模拟实现 - module + 函数式编程 - include + super（ancestors)
3. rack是什么？
4. • 定义web server(Thin / WebRick) 接⼝口 • 定义rack-based app 接⼝口（middleware） • 提供middleware
5. 每⼀一个middleware，本质上都是⼀一个rack- based app
6. rack-based app • 统⼀一⽅方法名：响应call⽅方法 • 统⼀一参数：env（输⼊入request） • 统⼀一返回值：code, header, body（输出 response）
7. class ContentLength
 
 def initialize(app)
 @app = app
 end
 
 def call(env)
 status, headers, body = @app.call(env)
 
 headers[CONTENT_LENGTH] = body.length.to_s
 
 [status, headers, body]
 end
 
 end
8. 多个middleware如何协同 ⼯工作
9. 1. 为所有middleware初始化⼀一个实例对象 （initialize instance） 2. 在initialize的时候定义实例变量:@app 3. @app 是下⼀一个middleware 对象 4. 在当前call⽅方法中调⽤用@app.call(env)
11. # File lib/rack/builder.rb, line 81
 def use(middleware, *args, &block)
 if @map
 mapping, @map = @map, nil
 @use << proc { |app| generate_map app, mapping }
 end
 @use << proc { |app| middleware.new(app, *args, &block) }
 end 初始化所有middleware
12. 开始运⾏行 run Application 实际在web server中执⾏行
15. @app变量 在initia⽅方法定义 module Rack
 class ContentLength
 
 def initialize(app)
 @app = app
 end
 
 end
 end
16. 第⼀一个对象 Rack::ContentLength 的实例变量 @app
17. 字符：234358个
18. #<Rack::Lock:0x007fa65a8ab828>
 #<Daifu::Application:0x007fa653dfc720>
 #<Rack::Sendfile:0x007fa659a3eb50>
 #<ActionDispatch::Static:0x007fa659a3edd0>
 #<Rack::Lock:0x007fa659a3ee48>
 #<Rack::Runtime:0x007fa659a3ee98>
 #<Rack::MethodOverride:0x007fa659a3eec0>
 #<Rails::Rack::Logger:0x007fa659a3ef10>
 #<ActionDispatch::ShowExceptions:0x007fa659a3ef38>
 #<ActionDispatch::DebugExceptions:0x007fa659a3ef60>
 #<ActionDispatch::RemoteIp:0x007fa659a3ef88>
 #<ActionDispatch::Reloader:0x007fa659a3efb0>
 #<ActionDispatch::Callbacks:0x007fa659a3efd8>
 #<ActiveRecord::Migration::CheckPending:0x007fa659a3f000>
 #<ActiveRecord::ConnectionAdapters::ConnectionManagement:0x007fa659a3f140>
 #<ActiveRecord::QueryCache:0x007fa659a3f280>
 #<ActionDispatch::Cookies:0x007fa659a3f398>
 #<ActionDispatch::Session::CookieStore:0x007fa659a3f438>
 #<ActionDispatch::Flash:0x007fa659a3f460>
 #<ActionDispatch::ParamsParser:0x007fa659a3f528>
 #<Rack::Head:0x007fa659a3f550>
 #<Rack::ConditionalGet:0x007fa659a3f578>
 #<Rack::ETag:0x007fa659a3f5a0>
 #<ActionDispatch::Routing::RouteSet:0x007fa657658538>
19. 开始调⽤用第⼀一个中间件 status, headers, body = @app.call(env) 第⼀一个 middleware Rack::ContentLength
20. def call(env)
 status, headers, body = @app.call(env)
 
 # 对拿到返回的response进⾏行加⼯工
 headers['Content-Length'] = body.size 
 [status, headers, body]
 end 下⼀一个 middleware Rack::Lock 当前middleware Rack::ContentLength
21. def call(env)
 old, env[FLAG] = env[FLAG], false
 @mutex.lock
 response = @app.call(env)
 body = BodyProxy.new(response[2]) { @mutex.unlock }
 response[2] = body
 response
 end 下⼀一个 middleware Rails::Application 当前middleware Rack::Lock
22. def call(env)
 env.merge!(env_config)
 app.call(env)
 end 当前middleware Rails::Application 下⼀一个 middleware Rack::Sendfile
23. 
 def call(env)
 status, headers, body = @app.call(env)
 if body.respond_to?(:to_path)
 if type == 'X-Sendfile'
 path = F.expand_path(body.to_path)
 headers[CONTENT_LENGTH] = '0'
 headers[type] = path
 obody = body
 body = Rack::BodyProxy.new([]) do
 obody.close if obody.respond_to?(:close)
 end
 end
 end
 [status, headers, body]
 end 当前 middleware Rack::Sendfile 下⼀一个 middleware ……
26. def call(env)
 status, headers, body = @app.call(env)
 
 if etag_status?(status)
 headers[ETAG_STRING] = %(W/"#{digest}") if digest
 end
 
 unless headers[CACHE_CONTROL]
 headers[CACHE_CONTROL] = @cache_control if @cache_control
 end
 
 [status, headers, body]
 end 当前 middleware Rack::ETag 下⼀一个 middleware ActionDispatch::Routing::RouteSet
27. self #<Rack::ETag:0x007fe547a41918 @app=#<ActionDispatch::Routing::RouteSet: 0x007fe54560b558>, @cache_control="max-age=0, private, must-revalidate", @no_cache_control="no-cache">
28. #<ActionDispatch::Routing::RouteSet: 0x007f95a82b8870> @app
29. def call(env)
 req = request_class.new(env)
 req.path_info = Journey::Router::Utils.normalize_path(req.path_info)
 @router.serve(req)
 end 当前 middleware ActionDispatch::Routing::RouteSet 下⼀一个 middleware？ ActionDispatch::Journey::Router
30. 谁是最后⼀一个 middleware
31. 这不是重点
32. def serve(req)
 find_routes(req).each do |match, parameters, route|
 set_params = req.path_parameters
 path_info = req.path_info
 script_name = req.script_name
 
 unless route.path.anchored
 req.script_name = (script_name.to_s + match.to_s).chomp('/')
 req.path_info = match.post_match
 req.path_info = "/" + req.path_info unless req.path_info.start_with? "/"
 end
 
 req.path_parameters = set_params.merge parameters
 
 status, headers, body = route.app.serve(req)
 
 if 'pass' == headers['X-Cascade']
 req.script_name = script_name
 req.path_info = path_info
 req.path_parameters = set_params
 next
 end
 
 return [status, headers, body]
 end
 
 return [404, {'X-Cascade' => 'pass'}, ['Not Found']]
 end ActionDispatch::Journey::Router
33. 补充⼀一些好玩的ruby知识
34. #< Rack::ETag:0x007fa659a3f5a0 @app=#<ActionDispatch::Routing::RouteSet:0x007fa657658538>, @cache_control="max-age=0, private, must-revalidate", @no_cache_control=“no-cache" > Ruby Object Notation（ruby 对象表⽰示法，RON)
35. { "app": "#<ActionDispatch::Routing::RouteSet:0x007ff9dfb4b848>", "cache_control": "max-age=0, private, must-revalidate", "no_cache_control": "no-cache" } @instance.instance_values
36. middleware基本就是做这样⼏几件事 • 修改参数 • 修改body • 修改headers • 修改status code
37. • 开销1：提前初始化所有Middleware • 开销2：@app变量占⽤用内存较⾼高（包含所有剩余 的中间件信息）
38. 题外话：为什么⾯面向对象的程序语⾔言性能往往 不如函数式编程语⾔言？
39. middleware们 • 按⼀一定顺序分解并处理任务 • 能够调整位置
40. • 统⼀一的⽅方法：call • 统⼀一的信息传递：env • 统⼀一的返回：[]
41. 递归调⽤用的特点 • 原路返回 • 调⽤用堆栈越深越消耗性能
42. 模拟middleware
43. module + 函数式编程
44. 函数式编程：ruby是⾯面向对象的语⾔言中对函数 式编程⽀支持的最完美的语⾔言 ⾯面向对象编程：ruby是最纯粹的⾯面向对象的语⾔言
45. 演⽰示代码
46. module + ancestors
47. • include • prepend • ancestors
48. 演⽰示代码
49. Any Question?