微服务网关Zuul服务降级

当消费者调用提供者时由于各种原因出现无法调用的情况时，消费者可以进行服务降级。那么，若客户端通过网关调用消费者无法调用时，zuul具有服务降级功能。

一、基本环境搭建

• 一个eureka项目
• 一个zuul项目

二、创建网关zuul

（1）创建项目00-zuul-fallback-9000

（2）依赖

    4.0.0

    com.abc
    00-zuul-fallback-9000
    0.0.1-SNAPSHOT
    jar

    
        org.springframework.boot
        spring-boot-starter-parent
        2.1.3.RELEASE
         
    

    
        1.8
        Greenwich.SR1
    

    
        
            org.projectlombok
            lombok
            true
        
        
            org.springframework.boot
            spring-boot-starter-actuator
        
        
            org.springframework.cloud
            spring-cloud-starter-netflix-eureka-client
        
        
        
            org.springframework.cloud
            spring-cloud-starter-netflix-zuul
        
    


    
        
            
                org.springframework.cloud
                spring-cloud-dependencies
                ${spring-cloud.version}
                pom
                import
            
        
    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    

（3）application.yml配置

server:
  port: 9000

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8000/eureka

spring:
  application:
    name: abcmsc-zuul-depart

zuul:
  routes:
    # 指定微服务的路由规则
    abcmsc-consumer-depart-8080: /abc8080/**
    abcmsc-consumer-depart-8090: /abc8090/**

（4）降级类

package com.abc.zuul.fallback;

import org.springframework.cloud.netflix.zuul.filters.route.FallbackProvider;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.stereotype.Component;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;

@Component
public class ConsumerFallback implements FallbackProvider {

    // 指定要降级的微服务名称
    @Override
    public String getRoute() {
        // 对所有微服务降级
        return "*";
        // 仅对指定的微服务进行降级
        // return "abcmsc-consumer-depart-8080";
    }

    // 定制降级响应
    // route参数：当前请求所访问的微服务名称
    @Override
    public ClientHttpResponse fallbackResponse(String route, Throwable cause) {
        System.out.println("route = " + route);
        return new ClientHttpResponse() {
            @Override
            public HttpStatus getStatusCode() throws IOException {
                // 返回状态常量
                return HttpStatus.SERVICE_UNAVAILABLE;
            }

            @Override
            public int getRawStatusCode() throws IOException {
                // 返回状态码，这里为503
                return HttpStatus.SERVICE_UNAVAILABLE.value();
            }

            @Override
            public String getStatusText() throws IOException {
                // 返回状态码对应的状态短语，这里为"Service Unavailable"
                return HttpStatus.SERVICE_UNAVAILABLE.getReasonPhrase();
            }

            @Override
            public void close() { }

            @Override
            public InputStream getBody() throws IOException {
                // 设置降级信息
                // String msg = "fallback:" + ConsumerFallback.this.getRoute();
                String msg = "fallback:" + route;
                return new ByteArrayInputStream(msg.getBytes());
            }

            @Override
            public HttpHeaders getHeaders() {
                // 设置降级响应头信息
                HttpHeaders headers = new HttpHeaders();
                headers.setContentType(MediaType.APPLICATION_JSON);
                return headers;
            }
        };
    }
}

（5）启动类

package com.abc.zuul;

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

@EnableZuulProxy    // 开启zuul代理模式
@SpringBootApplication
public class ZuulApplication {

    public static void main(String[] args) {
        SpringApplication.run(ZuulApplication.class, args);
    }

}

三、创建eureka

（1）创建00-eurekaserver-8000项目

（2）依赖

    4.0.0

    com.abc
    00-eurekaserver-8000
    0.0.1-SNAPSHOT
    jar

    
        org.springframework.boot
        spring-boot-starter-parent
        2.1.7.RELEASE
         
    

    
        1.8
        Greenwich.SR2
    

    
        
            org.springframework.cloud
            spring-cloud-starter-netflix-eureka-server
        

        
            org.springframework.boot
            spring-boot-starter-test
            test
        
    

    
        
            
                org.springframework.cloud
                spring-cloud-dependencies
                ${spring-cloud.version}
                pom
                import
            
        
    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    

（3）application.yml配置

server:
  port: 8000

eureka:
  instance:
    hostname: localhost  # 指定Eureka主机
  client:
    register-with-eureka: false   # 指定当前主机是否向Eureka服务器进行注册
    fetch-registry: false    # 指定当前主机是否要从Eurka服务器下载服务注册列表
    service-url:   # 服务暴露地址
     defaultZone: http://localhost:8000/eureka
#     defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka

#  server:
#    enable-self-preservation: false    # 关闭自我保护

（4）启动类

package com.abc.eureka;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer   // 开启Eureka服务
public class EurekaServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class, args);
    }
}

四、测试

（1）启动eureka

（2）启动zuul网关

（3）效果

访问 ：http://localhost:9000//abc8080/consumer/depart/get/1被降级处理

访问 ：http://localhost:9000//abc8090/consumer/depart/get/1被降级处理