前言

Github：https://github.com/yihonglei/thinking-in-springcloud

Eureka注册中心：eureka-server

服务提供者（订单服务）：eureka-provider-order

ribbon消费（用户服务）：eureka-consumer-ribbon

一 Ribbon概要

Ribbon是一个基于HTTP和TCP的客户端负载均衡器，Ribbon与Eureka结合使用时，

Ribbon会从Eureka注册中心获取服务端列表，通过某种轮询方式，达到负载均衡访问服务。

二启动eureka-server（注册中心）

执行eureka-server项目EurekaServerApplication类的main方法。

三启动eureka-provider-order（服务提供者）

1、注释掉eureka-provider-order配置文件application.properties中的instance-id配置，

使用默认配置，否则

eureka.instance.instance-id=eureka-provider-order-8001

2、打包eureka-provider-order项目，通过命令行启动两个服务。

java -jar eureka-provider-order-1.0-SNAPSHOT.jar —server.port=8081

java -jar eureka-provider-order-1.0-SNAPSHOT.jar —server.port=8082

启动后查看eureka注册中心，会发现注册了eureka-provider-order的8081，8082端口服务。

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四启动eureka-consumer-ribbon（服务消费者）

1、eureka-consumer-ribbon项目结构

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2、pom.xml依赖

引入Ribbon模块依赖。

<!-- Eureka Client -->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<!-- Ribbon负载均衡依赖 -->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>

3、application.properties

配置应用名称，服务端口，注册中心。

# 注册到eureka服务端的微服务名称
spring.application.name=eureka-consumer-ribbon
# 服务提供端口
server.port=8004
# 注册到eureka服务端的地址
eureka.client.service-url.defaultZone=http://localhost:9000/eureka/
# 显示指定微服务的名称，默认ip:应用名称:端口(192.168.1.7:eureka-consumer-ribbon:8004)
eureka.instance.instance-id=eureka-consumer-ribbon-8004
eureka.instance.prefer-ip-address=true

4、MainConfig

创建RestTemplate应用实例，通过@LoadBalanced注解开启客户端负载均衡。

package com.jpeony.ribbon.config;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;
/**
 * RestTemplate创建
 *
 * @author yihonglei
 */
@Configuration
public class MainConfig {
    @LoadBalanced
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

5、UserController控制类

通过RestTemplate发起服务访问，而不是具体的地址。

package com.jpeony.ribbon.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
/**
 * -- @RestController这个注解等价于spring mvc用法中的@Controller+@ResponseBody
 *
 * @author yihonglei
 */
@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private RestTemplate restTemplate;
    @RequestMapping(value = "/queryUserInfo", method = {RequestMethod.GET, RequestMethod.POST})
    public String queryUserInfo() {
        ResponseEntity<String> responseEntity =
                restTemplate.getForEntity("http://EUREKA-PROVIDER-ORDER/order/queryOrderInfo", String.class);
        return responseEntity.getBody();
    }
}

6、ConsumerRibbonApplication应用启动

通过注解@EnableDiscoveryClient让应用注册到Eureka客户端，具有获取服务发现的能力。

package com.jpeony.ribbon;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
/**
 * -- @SpringBootApplication 启动一个Spring Boot应用程序
 * -- @EnableDiscoveryClient 服务发现与注册，当应用启动时，将应用注册到配置的注册中心
 *
 * @author yihonglei
 */
@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerRibbonApplication {
    public static void main(String[] args) {
        SpringApplication.run(ConsumerRibbonApplication.class, args);
    }
}

7、运行RibbonConsumerApplication类启动服务

注册中心多了eureka-consumer-ribbon服务。

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五访问eureka-consumer-ribbon服务，通过ribbon负载，

消费eureka-provider-order服务

http://localhost:8004/user/queryUserInfo

Ribbon从服务端获取eureka-consumer-ribbon服务列表，包含各个实例的位置，

然后Ribbon按照列表信息进行轮询访问，实现基于客户端的负载均衡。

关于eureka-consumer-ribbon访问时控制台打印的关于客户端负载均衡日志。

2019-06-22 17:02:08.118  INFO 90932 --- [nio-8004-exec-1] c.n.l.DynamicServerListLoadBalancer: 
DynamicServerListLoadBalancer for client EUREKA-PROVIDER-ORDER initialized: 
-- 服务列表
DynamicServerListLoadBalancer:{NFLoadBalancer:name=EUREKA-PROVIDER-ORDER,
current list of Servers=[192.168.102.186:8081, 192.168.102.186:8082],
-- 负载均衡
Load balancer stats=Zone stats: 
{
    defaultzone=[
        Zone:defaultzone;    Instance count:2;    
        Active connections count: 0;    
        Circuit breaker tripped count: 0;    
        Active connections per server: 0.0;
    ]
},
-- 服务状态
Server stats: [
    [
        Server:192.168.102.186:8082;    
        Zone:defaultZone;    
        Total Requests:0;    
        Successive connection failure:0;    
        Total blackout seconds:0;    
        Last connection made:Thu Jan 01 08:00:00 CST 1970;    
        First connection made: Thu Jan 01 08:00:00 CST 1970;    
        Active Connections:0;    
        total failure count in last (1000) msecs:0;    
        average resp time:0.0;    
        90 percentile resp time:0.0;    
        95 percentile resp time:0.0;    
        min resp time:0.0;    
        max resp time:0.0;    
        stddev resp time:0.0
    ], 
    [
        Server:192.168.102.186:8081;    
        Zone:defaultZone;    
        Total Requests:0;    
        Successive connection failure:0;    
        Total blackout seconds:0;    
        Last connection made:Thu Jan 01 08:00:00 CST 1970;    
        First connection made: Thu Jan 01 08:00:00 CST 1970;    
        Active Connections:0;    
        total failure count in last (1000) msecs:0;    
        average resp time:0.0;    
        90 percentile resp time:0.0;    
        95 percentile resp time:0.0;    
        min resp time:0.0;    
        max resp time:0.0;    
        stddev resp time:0.0
    ]
]}
ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@7abc34b6
2019-06-22 17:02:09.106  INFO 90932 --- [erListUpdater-0] c.netflix.config.ChainedDynamicProperty: 
Flipping property: 
 EUREKA-PROVIDER-ORDER.ribbon.ActiveConnectionsLimit to use NEXT property: 
 niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647