第二章微服务网关基础组件 - zuul入门

向右看齐 2022-05-10 01:26 162阅读 0赞

[开发十年，就只剩下这套Java开发体系了 >>> ][Java_ _]  ![hot3.png][]

**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/][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）**

![866881-20170106171654316-977255062.png][]

说明：对应（二）的filter type来看

**四、zuul核心架构**

![866881-20170106191748566-1274562936.png][]

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。

[Java_ _]: https://my.oschina.net/u/3779583/blog/1862418
[hot3.png]: /images/20220510/878d47c3959a4c0f81dfb77893cf5501.png
[Filters]: https://github.com/Netflix/zuul/wiki/Filters
[https_github.com_Netflix_zuul]: https://github.com/Netflix/zuul/
[866881-20170106171654316-977255062.png]: /images/20220510/4596659d0b2f4f68a08f94f2334b8fed.png
[866881-20170106191748566-1274562936.png]: /images/20220510/1d27e34355c04424a269196c3ebcc5ec.png