Zuul简介及代码示例

zuul它是一种怪兽,可能是因为长相太可怕了,百度居然搜不到,我们打开Spring Cloud文档

https://cloud.spring.io/spring-cloud-netflix/reference/html/#_router_and_filter_zuul

Router and Filter: Zuul

路由器和过滤器Zuul

在2微服务架构里面呢,路由是微服务架构的一部分,根路径会映射到你的WEB引用,/api/user他可能会映射到用户

微服务,这个路径会映射到你的商店微服务,Zuul是Netflix开发的,基于JVM的,路由器和服务器端的负载均衡器,我们之前

讲过客户端负载均衡机制,Ribbon,Zuul他还是服务端的负载均衡

Routing is an integral part of a microservice architecture. For example, / may be mapped to your 

web application, /api/users is mapped to the user service and /api/shop is mapped to the 

shop service. Zuul is a JVM-based router and server-side load balancer from Netflix.

认证,压力测试,动态路由,服务的迁移,减轻各个负载,静态的响应处理,还有流量的管理

Netflix uses Zuul for the following:

Authentication

Insights

Stress Testing

Canary Testing

Dynamic Routing

Service Migration

Load Shedding

Security

Static Response handling

Active/Active traffic management

Zuul的规则引擎呢,使用任意的JVM语言写的,内置可以使用JAVA和Groovy,但是理论上所有的JVM语言都可以玩,

Zuul’s rule engine lets rules and filters be written in essentially any JVM language, 

with built-in support for Java and Groovy.

这个配置项被两个配置项代替了

The configuration property zuul.max.host.connections has been replaced by two new properties, 

zuul.host.maxTotalConnections and zuul.host.maxPerRouteConnections, 

which default to 200 and 20 respectively.

隔离一个是SEMAPHORE,一个是THREAD,一个是信号,一个是线程,他在这个里面使用的信号,你也可以使用这个配置,

去把它指定成Thread

The default Hystrix isolation pattern (ExecutionIsolationStrategy) for all routes is SEMAPHORE. 

zuul.ribbonIsolationStrategy can be changed to THREAD if that isolation pattern is preferred.

http://www.github.com/netflix/hystrix

我们讲hystrix的时候有讲过他的隔离

https://github.com/netflix/hystrix/wiki

https://github.com/Netflix/Hystrix/wiki/Configuration

一个是THREAD,一个是SEMAPHORE,他说了默认的是Thread

How to Include Zuul

你要在Spring Cloud里面引入某个组建的话,你就要加上某某starter

To include Zuul in your project, use the starter with a group ID of org.springframework.cloud 

and a artifact ID of spring-cloud-starter-netflix-zuul. 

Spring Cloud创建了一个嵌入式的代理,他去简化了一种非常常见的开发,开发的方式,这种方式是什么呢,

其中UI应用程序想要去代理,一个或者是多个后端的服务的调用,他说这种特性呢,他说这种特性是比较有用的,

对于用户界面他去代理,后端的服务,对于所有后端去处理跨域,和认证的需要,CORS是Cross Orginal Resouce 

Sharing,其实就是跨域请求,可以这样理解,如果你想要使用它的话,在你的主类加上@EnableZuulProxy,本地的请求

会转发到相应的服务,按照约定,假设一个服务它的ID是users,它会用这种路径去接收请求,然后他把前缀省略掉了,

Zuul他使用的是Ribbon,通过Ribbon查询服务注册的组件,Eureka转发你要的实例,所有的请求都会在Hystrix Command

里面去执行,我们之前解析过了Hystrix Command是什么东西了,所有使用@HystrixCommand这个注解,这样所有的失败

都会在Hystrix的指标里面去显示,因为断路器都打开了,不会请求远程的服务了,相对于后端的服务Zuul

Spring Cloud has created an embedded Zuul proxy to ease the development of a common use case where 

a UI application wants to make proxy calls to one or more back end services. This feature is useful 

for a user interface to proxy to the back end services it requires, avoiding the need to manage CORS 

and authentication concerns independently for all the back ends.

To enable it, annotate a Spring Boot main class with @EnableZuulProxy. Doing so causes local calls 

to be forwarded to the appropriate service. By convention, a service with an ID of users receives 

requests from the proxy located at /users (with the prefix stripped). The proxy uses Ribbon to 

locate an instance to which to forward through discovery. All requests are executed in a hystrix 

command, so failures appear in Hystrix metrics. Once the circuit is open, the proxy does not 

try to contact the service.

Zuul其实并没有发现服务发现的客户端,他没有包含Eureka的Client,因此如果你想通过serviceId去路由的话,

你得提供依赖

microservice-gateway-zuul

<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-zuul</artifactId>
</dependency>

Zuul的依赖加好了,这个时候我们是不是还得加Eureka的依赖

the Zuul starter does not include a discovery client, so, for routes based on service IDs, 

you need to provide one of those on the classpath as well (Eureka is one choice).

@EnableZuulProxy
@SpringBootApplication
public class EurekaApplication {
  public static void main(String[] args) {
    SpringApplication.run(EurekaApplication.class, args);
  }
}

@EnableZuulProxy它是一个组合注解

@EnableCircuitBreaker
@EnableDiscoveryClient
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(ZuulProxyConfiguration.class)
public @interface EnableZuulProxy {
}

这就是为什么,我只要一个注解就可以把它注册到Eureka

localhost:7900/simple/1

localhost:8040/microservice-simple-provider-user/simple/1

所以这个就是Eureka里面的serviceId,

Mapped URL path [/microservice-simple-provider-user/**] onto handler of type 

[class org.springframework.cloud.netflix.zuul.web.ZuulController]

他其实是有一个映射的,规则也是非常简单的,比如你在eureka上有一个微服务叫abc,abc的端口

是8000,他有一个接口是/simple/1,我们使用zuul去访问的,abc是应用的名称,这就可以访问了,

但是没有完全达到我的要求,这么长一个我不喜欢,我想要改成user,我想改成这样的

localhost:8040/user/simple/1


zuul:
  routes:
    user-route:                   # 该配置方式中，user-route只是给路由一个名称，可以任意起名。
      service-id: microservice-provider-user
      path: /user/**              # service-id对应的路径
zuul.routes.user-route.service-id=microservice-simple-provider-user
zuul.routes.user-route.path=/user/** 

假设我现在有个user微服务,有个电影微服务,反向代理微服务,

默认所有注册到Eureka上的微服务

microservice-consumer-movie-ribbon-hystrix

localhost:8040/microservice-consumer-movie-ribbon-hystrix/movie/1

localhost:8010/movie/1

如果我只想代理user微服务,不想代理电影微服务,第一种办法是把所有的微服务ignore,只有你配的微服务才反向代理,

https://cloud.spring.io/spring-cloud-netflix/reference/html/#_router_and_filter_zuul

 zuul:
  ignoredServices: '*'
  routes:
    users: /myusers/**
	
第二种就是配置

zuul.ignoredServices=microservice-consumer-movie-ribbon-hystrix

多个我可以用逗号

/**
 * Set of service names not to consider for proxying automatically. By default all
 * services in the discovery client will be proxied.
 */
private Set<String> ignoredServices = new LinkedHashSet<>();

他是一个Set,我们可以用逗号分隔开

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.learn.cloud</groupId>
	<artifactId>microservice-gateway-zuul</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	 <parent>
	   <groupId>cn.learn</groupId>
	   <artifactId>microcloud02</artifactId>
	   <version>0.0.1</version>
	 </parent>
	
	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>	
	
	<dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka-server</artifactId>
            <version>1.4.2.RELEASE</version>
        </dependency>
		<dependency>
		    <groupId>org.springframework.cloud</groupId>
		    <artifactId>spring-cloud-starter-zuul</artifactId>
		</dependency>
	</dependencies>
	
	<!-- 这个插件,可以将应用打包成一个可执行的jar包 -->
	<build>
	    <plugins>
	        <plugin>
	            <groupId>org.springframework.boot</groupId>
	            <artifactId>spring-boot-maven-plugin</artifactId>
	        </plugin>
	    </plugins>
	</build>

  
</project>

server.port=8040
spring.application.name=microservice-gateway-zuul
eureka.instance.prefer-ip-address=true
eureka.instance.instance-id=${spring.application.name}:${spring.cloud.client.ipAddress}:${spring.application.instance_id:${server.port}}
eureka.client.serviceUrl.defaultZone=http://admin:[email protected]:8761/eureka
eureka.instance.appname=microservice-gateway-zuul
zuul.routes.user-route.service-id=microservice-simple-provider-user
#zuul.ignoredServices=microservice-consumer-movie-ribbon-hystrix
zuul.routes.user-route.path=/user/**

package com.learn.cloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;

@EnableZuulProxy
@SpringBootApplication
public class GateWayZuulApplication {
  public static void main(String[] args) {
    SpringApplication.run(GateWayZuulApplication.class, args);
  }
}