微服务网关基础组件 - zuul入门

未来已来2018-11-25 11:16

此文已由作者赵计刚薪授权网易云社区发布。

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一、zuul简介

1、作用

zuul使用一系列的filter实现以下功能

  • 认证和安全 - 对每一个resource进行身份认证
  • 追踪和监控 - 实时观察后端微服务的TPS、响应时间,失败数量等准确的信息
  • 日志 - 记录所有请求的访问日志数据,可以为日志分析和查询提供统一支持
  • 动态路由 - 动态的将request路由到后端的服务上去
  • 压力测试 - 逐渐的增加访问集群的压力,来测试集群的性能
  • 限流 - allocating capacity for each type of request and dropping requests that go over the limit
  • 静态响应 - 直接在网关返回一些响应,而不是通过内部的服务返回响应

2、组件:

  • zuul-core:library which contains the core functionality of compiling and executing Filters
  • zuul-netflix:library which adds other NetflixOSS components to Zuul - using Ribbon for routing requests, for example.

3、例子:

  • zuul-simple-webapp:webapp which shows a simple example of how to build an application with zuul-core
  • zuul-netflix-webapp:webapp which packages zuul-core and zuul-netflix together into an easy to use package

github地址:https://github.com/Netflix/zuul/

 

二、zuul filter

1、关键元素

  • Type:most often defines the stage during the routing flow when the Filter will be applied (although it can be any custom string)
    • 值可以是:pre、route、post、error、custom
  • Execution Order: filter执行的顺序(applied within the Type, defines the order of execution across multiple Filters)
  • Criteria:filter执行的条件(the conditions required in order for the Filter to be executed)
  • Action: filter执行的动作(the action to be executed if the Criteria is met)

注意点:

  • filters之间不会直接进行通讯交流,他们通过一个RequestContext共享一个state
    • 该RequestContext对于每一个request都是唯一的
  • filter当前使用groovy来写的,也可以使用java
  • The source code for each Filter is written to a specified set of directories on the Zuul server that are periodically polled for changes
  • zuul可以动态的read, compile, and run these Filters
    • 被更新后的filter会被从disk读取到内存,并动态编译到正在运行的server中,之后可以用于其后的每一个请求(Updated filters are read from disk, dynamically compiled into the running server, and are invoked by Zuul for each subsequent request)

2、filter type(与一个典型的request的生命周期相关的filter type)

  • PRE Filters
    • 执行时机: before routing to the origin.
    • 这类filter可能做的事
      • request authentication
      • choosing origin servers(选机器)
      • logging debug info.
      • 限流
  • ROUTING Filters
    • 这类filter可能做的事:真正的向service的一台server(这台server是pre filter选出来的)发请求,handle routing the request to an origin,This is where the origin HTTP request is built and sent using Apache HttpClient or Netflix Ribbon.
  • POST Filters
    • 执行时机:after the request has been routed to the origin
    • 这类filter可能做的事
      • adding standard HTTP headers to the response
      • gathering statistics and metrics
      • streaming the response from the origin to the client
  • ERROR Filters
    • 执行时机:其他三个阶段任一阶段发生错误时执行(when an error occurs during one of the other phases)
  • CUSTOM Filters
    • 沿着默认的filter流,zuul允许我们创建一些自定义的Filter type,并且准确的执行他们。
    • 例如:我们自定义一个STATIC type的filter,用于从zuul直接产生响应,而不是从后边的services(we have a custom STATIC type that generates a response within Zuul instead of forwarding the request to an origin)

 

三、zuul request lifecycle(filter流)


说明:对应(二)的filter type来看

 

四、zuul核心架构


zuul的核心就是:filter、filter流与核心架构。这些在下一章会以代码的形式做展示。


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