12.SpringCloud学习笔记--Ribbon

Ribbon入门介绍

是什么

Spring Cloud Ribbon是基于Netflix Ribbon实现的一套客户端负载均衡的工具。

简单的说，Ribbon是Netflix发布的开源项目，主要功能是提供客户端的软件负载均衡算法，将Netflix的中间层服务连接在一起。Ribbon客户端组件提供一系列完善的配置项如连接超时，重试等。简单的说，就是在配置文件中列出Load Balancer（简称LB）后面所有的机器，Ribbon会自动的帮助你基于某种规则（如简单轮询，随机连接等）去连接这些机器。我们也很容易使用Ribbon实现自定义的负载均衡算法。

官网资料

https://github.com/Netflix/ribbon/wiki/Getting-Started

https://github.com/Netflix/ribbon

Project Status: On Maintenance

Ribbon comprises of multiple components some of which are used in production internally and some of which were replaced by non-OSS solutions over time. This is because Netflix started moving into a more componentized architecture for RPC with a focus on single-responsibility modules. So each Ribbon component gets a different level of attention at this moment.

More specifically, here are the components of Ribbon and their level of attention by our teams:

ribbon-core: deployed at scale in production

ribbon-eureka: deployed at scale in production

ribbon-evcache: not used

ribbon-guice: not used

ribbon-httpclient: we use everything not under com.netflix.http4.ssl. Instead, we use an internal solution developed by our cloud security team

ribbon-loadbalancer: deployed at scale in production

ribbon-test: this is just an internal integration test suite

ribbon-transport: not used

ribbon: not used

用途

负载均衡LB（Load Banlance）是什么？

简单的说就是将用户的请求平摊的分配到多个服务上，从而达到系统的HA（高可用）。

常见的负载均衡有软件Nginx，LVS，硬件 F5等。

Ribbon本地负载均衡客户端与Nginx服务器端负载均衡区别

Nginx是服务器负载均衡，客户端所有请求交给 Nginx，然后由 Nginx 实现转发请求。即负载均衡是由服务器端实现，集中式LB。
Ribbon是本地负载均衡，在调用微服务接口时候，会在注册中心上获取注册信息服务列表之后缓存到 JVM 本地，从而在本地实现 RPC 远程服务调用技术。即在客户端实现负载均衡，进程内LB。

由上面的区别可以将负载均衡分为两种：

集中式LB：在服务的消费方和提供方之间使用独立的LB设施（Nginx）
进程内LB：将LB的逻辑继承到消费方，消费方从服务注册中心获知哪些提供方地址可用，然后自己进行选择（Ribbon）

Ribbon就是一个软负载均衡的客户端组件，就是负载均衡+RestTemplate调用

Ribbon的负载均衡和Rest调用

Ribbon就是一个软负载均衡的客户端组件，他可以和其他所需请求的客户端结合使用，和eureka结合只是其中的一个实例。

在这里插入图片描述

Ribbon在工作时分成两步：

第一步先选择 EurekaServer ,它优先选择在同一个区域内负载较少的server；

第二步再根据用户指定的策略，在从server取到的服务注册列表中选择一个地址。

其中Ribbon提供了多种策略：比如轮询、随机和根据响应时间加权。

之前实现了负载均衡就是基于 Ribbon，其实在使用eureka的新版本时，默认就集成了Ribbon。

<!--eureka client-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

单独引入ribbon

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

RestTemplate的使用

官网：https://docs.spring.io/spring-framework/docs/5.2.2.RELEASE/javadoc-api/org/springframework/web/client/RestTemplate.html

`<T> ResponseEntity<T>`	`getForEntity(String url, Class responseType, Map uriVariables)`Retrieve a representation by doing a GET on the URI template.
`<T> ResponseEntity<T>`	`getForEntity(String url, Class responseType, Object... uriVariables)`Retrieve an entity by doing a GET on the specified URL.
`<T> ResponseEntity<T>`	`getForEntity(URI url, Class responseType)`Retrieve a representation by doing a GET on the URL .
`T`	`getForObject(String url, Class responseType, Map uriVariables)`Retrieve a representation by doing a GET on the URI template.
`T`	`getForObject(String url, Class responseType, Object... uriVariables)`Retrieve a representation by doing a GET on the specified URL.
`T`	`getForObject(URI url, Class responseType)`Retrieve a representation by doing a GET on the URL .

`<T> ResponseEntity<T>`	`postForEntity(String url, Object request, Class responseType, Map uriVariables)`Create a new resource by POSTing the given object to the URI template, and returns the response as `HttpEntity`.
`<T> ResponseEntity<T>`	`postForEntity(String url, Object request, Class responseType, Object... uriVariables)`Create a new resource by POSTing the given object to the URI template, and returns the response as `ResponseEntity`.
`<T> ResponseEntity<T>`	`postForEntity(URI url, Object request, Class responseType)`Create a new resource by POSTing the given object to the URL, and returns the response as `ResponseEntity`.
`T`	`postForObject(String url, Object request, Class responseType, Map uriVariables)`Create a new resource by POSTing the given object to the URI template, and returns the representation found in the response.
`T`	`postForObject(String url, Object request, Class responseType, Object... uriVariables)`Create a new resource by POSTing the given object to the URI template, and returns the representation found in the response.
`T`	`postForObject(URI url, Object request, Class responseType)`Create a new resource by POSTing the given object to the URL, and returns the representation found in the response.

getForObject / postForObject（推荐使用）

返回对象为响应体中数据转化成的对象，基本上可以理解为Json

@GetMapping("/consumer/payment/get/{id}")
public CommonResult<Payment> getPayment(@PathVariable("id") Long id){
    return restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id,CommonResult.class);
}

@GetMapping("/consumer/payment/create")
public CommonResult<Payment> create(Payment payment){
    return restTemplate.postForObject(PAYMENT_URL + "/payment/create",payment,CommonResult.class);

}

getForEntity / postForEntity

返回对象为ResponseEntity对象，包含了响应中的一些重要信息，比如响应头、相应状态码，响应体等

@GetMapping("/consumer/payment/getForEntity/{id}")
public CommonResult<Payment> getPayment2(@PathVariable("id") Long id)
{
    ResponseEntity<CommonResult> entity = restTemplate.getForEntity(PAYMENT_URL+"/payment/get/"+id,CommonResult.class);

    if(entity.getStatusCode().is2xxSuccessful()){
        return entity.getBody();
    }else{
        return new CommonResult<>(444,"操作失败");
    }
}

@GetMapping("/consumer/payment/postForEntity/create")
public CommonResult<Payment> create2(Payment payment){
    return restTemplate.postForEntity(PAYMENT_URL + "/payment/create",payment,CommonResult.class).getBody();

}

修改后的cloud-consumer-order80\src\main\java\demo\yangxu\springcloud\controller\OrderController.java

package demo.yangxu.springcloud.controller;

import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import javax.annotation.Resource;

@RestController
@Slf4j
public class OrderController {

    public static final String PAYMENT_URL = "http://CLOUD-PAYMENT-SERVICE";

    @Resource
    private RestTemplate restTemplate;

    @GetMapping("/consumer/payment/create")
    public CommonResult<Payment> create(Payment payment){
        return restTemplate.postForObject(PAYMENT_URL + "/payment/create",payment,CommonResult.class);

    }

    @GetMapping("/consumer/payment/postForEntity/create")
    public CommonResult<Payment> create2(Payment payment){
        return restTemplate.postForEntity(PAYMENT_URL + "/payment/create",payment,CommonResult.class).getBody();

    }

    @GetMapping("/consumer/payment/get/{id}")
    public CommonResult<Payment> getPayment(@PathVariable("id") Long id){
        return restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id,CommonResult.class);
    }

    @GetMapping("/consumer/payment/getForEntity/{id}")
    public CommonResult<Payment> getPayment2(@PathVariable("id") Long id) {
        ResponseEntity<CommonResult> entity = restTemplate.getForEntity(PAYMENT_URL+"/payment/get/"+id,CommonResult.class);

        if(entity.getStatusCode().is2xxSuccessful()){
            log.info(entity.getStatusCode()+"\t" + entity.getHeaders());
            return entity.getBody();
        }else{
            return new CommonResult<>(444,"操作失败");
        }
    }
}

测试

http://localhost/consumer/payment/getForEntity/31

{"code":200,"message":"查询成功,serverPort:8002","data":{"id":31,"serial":"aaabbb01"}}

日志信息

2020-07-23 20:08:10.760  INFO 5608 --- [p-nio-80-exec-1] d.y.s.controller.OrderController         : 200 OK	[Content-Type:"application/json", Transfer-Encoding:"chunked", Date:"Thu, 23 Jul 2020 12:08:10 GMT", Keep-Alive:"timeout=60", Connection:"keep-alive"]

Ribbon默认自带的负载规则

IRule: 根据特定算法中从服务列表中选取一个要访问的服务

在这里插入图片描述

com.netflix.loadbalancer.RoundRobinRule：轮询
com.netflix.loadbalancer.RandomRule：随机
com.netflix.loadbalancer.RetryRule：先按照RoundRobinRule的策略获取服务，如果获取服务失败则在指定时间内会进行重试，获取可用的服务
WeightedResponseTimeRule：对RoundRobinRule的扩展，响应速度越快的实例选择权重越大，越容易被选择
BestAvailableRule：会先过滤掉由于多次访问故障而处于断路器跳闸状态的服务，然后选择一个并发量最小的服务
AvailabilityFilteringRule：先过滤掉故障实例，再选择并发较小的实例
ZoneAvoidanceRule：默认规则，复合判断server所在区域的性能和server的可用性选择服务器

Ribbon负载规则替换

修改cloud-consumer-order80

注意配置细节

规则：这个自定义配置类不能放在 @ComponentScan 所扫描的当前包下以及子包下，否则自定义的配置类就会被所有的 Ribbon 客户端所共享，达不到特殊化定制的目的了。而 @ComponentScan 所扫描的当前包下以及子包下则就是 Spring Boot 主程序所在的包下，因为 @SpringBootApplication 注解里就包含 @ComponentScan。

Customizing the Ribbon Client

You can configure some bits of a Ribbon client using external properties in <client>.ribbon.*, which is no different than using the Netflix APIs natively, except that you can use Spring Boot configuration files. The native options can be inspected as static fields in CommonClientConfigKey (part of ribbon-core).

Spring Cloud also lets you take full control of the client by declaring additional configuration (on top of the RibbonClientConfiguration) using @RibbonClient. Example:
@Configuration
@RibbonClient(name = "foo", configuration = FooConfiguration.class)
public class TestConfiguration {
}
In this case the client is composed from the components already in RibbonClientConfiguration together with any in FooConfiguration (where the latter generally will override the former).

Warning The FooConfiguration has to be @Configuration but take care that it is not in a @ComponentScan for the main application context, otherwise it will be shared by all the @RibbonClients. If you use @ComponentScan (or @SpringBootApplication) you need to take steps to avoid it being included (for instance put it in a separate, non-overlapping package, or specify the packages to scan explicitly in the @ComponentScan).

参考：https://bushkarl.gitbooks.io/spring-cloud/content/spring_cloud_netflix/client_side_load_balancer_ribbon.html

新建package: demo.yangxu.myrule

上面的包下新建MySelfRule规则类

demo.yangxu.myrule.MySelfRule

package demo.yangxu.myrule;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MySelfRule {

    @Bean
    public IRule myRule(){
        
        //轮询
        //return new RoundRobinRule();
        
        //随机
        return new RandomRule();
        
        //先按照RoundRobinRule的策略获取服务，如果获取服务失败则在指定时间内会进行重试，获取可用的服务
        //return new RetryRule();
        
        //对RoundRobinRule的扩展，响应速度越快的实例选择权重越大，越容易被选择
        //return new WeightedResponseTimeRule();
        
        //会先过滤掉由于多次访问故障而处于断路器跳闸状态的服务，然后选择一个并发量最小的服务
        //return new BestAvailableRule();
        
        //先过滤掉故障实例，再选择并发较小的实例
        //return new AvailabilityFilteringRule();
        
        //默认规则，复合判断server所在区域的性能和server的可用性选择服务器
        //return new ZoneAvoidanceRule();
    }
}

主启动类添加@RibbonClient

demo.yangxu.springcloud.OrderMain80

package demo.yangxu.springcloud;

import demo.yangxu.myrule.MySelfRule;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.ribbon.RibbonClient;

@SpringBootApplication
@EnableEurekaClient
@RibbonClient(name = "CLOUD-PAYMENT-SERVICE",configuration = MySelfRule.class)
public class OrderMain80 {
    public static void main(String[] args) {
        SpringApplication.run(OrderMain80.class,args);
    }
}

测试

启动

EurekaMain7001
EurekaMain7002
PaymentMain8001
PaymentMain8002
OrderMain80

访问：http://localhost/consumer/payment/get/31

使用RandomRule的参考结果：

{"code":200,"message":"查询成功,serverPort:8002","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8001","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8002","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8001","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8001","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8001","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8002","data":{"id":31,"serial":"aaabbb01"}}{"code":200,"message":"查询成功,serverPort:8002","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8001","data":{"id":31,"serial":"aaabbb01"}}
{"code":200,"message":"查询成功,serverPort:8002","data":{"id":31,"serial":"aaabbb01"}}

Ribbon默认负载轮训算法原理

负载均衡算法

轮询算法：

rest 接口第几次请求数 % 服务器集群总数量 = 时机调用服务器位置下标

每次服务重启后 rest 接口计数从 1 开始。

List<ServiceInstance> instances = discoverClient.getInstances("CLOUD-PROVIDER-SERVICE");

如： List [0] instances = 127.0.0.1:8002

List[1] instances = 127.0.0.1:8001

8001 + 8002 组合为集群，共计 2 台服务器，集群总数为 2 ，按照轮询算法原理：

当请求总数为 1 时：1%2 = 1, 对应下标位置为 1，则获得服务地址为 127.0.0.1：8001
当请求总数为 2 时：2%2 = 0, 对应下标位置为 0，则获得服务地址为 127.0.0.1：8002
当请求总数为 3 时：2%2 = 1, 对应下标位置为 1，则获得服务地址为 127.0.0.1：8001

例如我们现在有两台服务器用于负载均衡

请求次数	计算公式	取得下标
1	1%2=1	对应 127.0.0.1:8001
2	2%2=0	对应 127.0.0.1:8002
3	3%2=1	对应 127.0.0.1:8001
…	…	…

RoundRobinRule源码

/*
 *
 * Copyright 2013 Netflix, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package com.netflix.loadbalancer;

import com.netflix.client.config.IClientConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * The most well known and basic load balancing strategy, i.e. Round Robin Rule.
 *
 * @author stonse
 * @author Nikos Michalakis <[email protected]>
 *
 */
public class RoundRobinRule extends AbstractLoadBalancerRule {

    private AtomicInteger nextServerCyclicCounter;
    private static final boolean AVAILABLE_ONLY_SERVERS = true;
    private static final boolean ALL_SERVERS = false;

    private static Logger log = LoggerFactory.getLogger(RoundRobinRule.class);

    public RoundRobinRule() {
        nextServerCyclicCounter = new AtomicInteger(0);
    }

    public RoundRobinRule(ILoadBalancer lb) {
        this();
        setLoadBalancer(lb);
    }

    public Server choose(ILoadBalancer lb, Object key) {
        if (lb == null) {
            log.warn("no load balancer");
            return null;
        }

        Server server = null;
        int count = 0;
        while (server == null && count++ < 10) {
            List<Server> reachableServers = lb.getReachableServers();
            List<Server> allServers = lb.getAllServers();
            int upCount = reachableServers.size();
            int serverCount = allServers.size();

            if ((upCount == 0) || (serverCount == 0)) {
                log.warn("No up servers available from load balancer: " + lb);
                return null;
            }

            int nextServerIndex = incrementAndGetModulo(serverCount);
            server = allServers.get(nextServerIndex);

            if (server == null) {
                /* Transient. */
                Thread.yield();
                continue;
            }

            if (server.isAlive() && (server.isReadyToServe())) {
                return (server);
            }

            // Next.
            server = null;
        }

        if (count >= 10) {
            log.warn("No available alive servers after 10 tries from load balancer: "
                    + lb);
        }
        return server;
    }

    /**
     * Inspired by the implementation of {@link AtomicInteger#incrementAndGet()}.
     *
     * @param modulo The modulo to bound the value of the counter.
     * @return The next value.
     */
    private int incrementAndGetModulo(int modulo) {
        for (;;) {
            int current = nextServerCyclicCounter.get();
            int next = (current + 1) % modulo;
            if (nextServerCyclicCounter.compareAndSet(current, next))
                return next;
        }
    }

    @Override
    public Server choose(Object key) {
        return choose(getLoadBalancer(), key);
    }

    @Override
    public void initWithNiwsConfig(IClientConfig clientConfig) {
    }
}

Ribbon之手写轮询算法

7001 / 7002 集群启动

8001 / 8002 微服务改造

Controller

demo.yangxu.springcloud.controller.PaymentController

package demo.yangxu.springcloud.controller;

import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import demo.yangxu.springcloud.service.PaymentService;

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;
import java.util.List;

@RestController
@Slf4j
public class PaymentController {

    @Resource
    private PaymentService paymentService;

    @Resource
    private DiscoveryClient discoveryClient;

    @Value("${server.port}")
    private String serverPort;

    @PostMapping(value = "/payment/create")
    public CommonResult create(@RequestBody Payment payment){
        int result = paymentService.create(payment);
        log.info("*****插入结果：" + result);

        if(result > 0){
            return new CommonResult(200,"插入数据库成功,serverPort:"+serverPort,result);
        }else{
            return new CommonResult(444,"插入数据库失败",null);
        }
    }

    @GetMapping(value = "/payment/get/{id}")
    public CommonResult<Payment> getPaymentById(@PathVariable("id") Long id){
        Payment payment = paymentService.getPaymentById(id);
        log.info("*****查询结果：" + payment + "热部署测试123456");

        if(payment != null){
            return new CommonResult(200,"查询成功,serverPort:"+serverPort,payment);
        }else{
            return new CommonResult(444,"没有对应记录，查询ID："+id,null);
        }
    }

    @GetMapping(value="/payment/discovery")
    public Object discovery(){
        //服务清单列表
        List<String> services = discoveryClient.getServices();
        for (String element : services) {
            log.info("*******element: "+element);
        }

        //一个微服务下的全部实例
        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        for (ServiceInstance instance : instances) {
            log.info(instance.getServiceId()+"\t"+instance.getHost()+"\t"+instance.getPort()+"\t"+instance.getUri());
        }

        return this.discoveryClient;
    }

    @GetMapping(value = "/payment/lb")
    public String getPaymentLB(){
        return serverPort;
    }

}

80订单微服务改造

ApplicationContextBean去掉注解@LoadBalanced

demo.yangxu.springcloud.config.ApplicationContextConfig

LoadBalancer接口

demo.yangxu.springcloud.lb.LoadBalancer

package demo.yangxu.springcloud.lb;

import org.springframework.cloud.client.ServiceInstance;

import java.util.List;

public interface LoadBalancer {
    ServiceInstance instances(List<ServiceInstance> serviceInstances);
}

MyLB

demo.yangxu.springcloud.lb.MyLB

package demo.yangxu.springcloud.lb;

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

@Component
public class MyLB implements LoadBalancer {

    private AtomicInteger atomicInteger = new AtomicInteger(0);

    public final int getAndIncrement(){
        int current;
        int next;

        do {
            current = this.atomicInteger.get();
            next = current >= 2147483647 ? 0 : current+1;
        }while(!this.atomicInteger.compareAndSet(current,next));
        System.out.println("*****第几次访问，次数next: "+next);
        return next;
    }

    //负载均衡算法：rest接口第几次请求数 % 服务器集群总数量 = 实际调用服务器位置下标  ，每次服务重启动后rest接口计数从1开始。
    @Override
    public ServiceInstance instances(List<ServiceInstance> serviceInstances) {
        int index = getAndIncrement() % serviceInstances.size();
        return serviceInstances.get(index);
    }
}

OrderController

demo.yangxu.springcloud.controller.OrderController

package demo.yangxu.springcloud.controller;

import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import demo.yangxu.springcloud.lb.LoadBalancer;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import javax.annotation.Resource;
import java.net.URI;
import java.util.List;

@RestController
@Slf4j
public class OrderController {

    public static final String PAYMENT_URL = "http://CLOUD-PAYMENT-SERVICE";

    @Resource
    private RestTemplate restTemplate;

    @Resource
    private LoadBalancer loadBalancer;

    @Resource
    private DiscoveryClient discoveryClient;

    @GetMapping("/consumer/payment/create")
    public CommonResult<Payment> create(Payment payment){
        return restTemplate.postForObject(PAYMENT_URL + "/payment/create",payment,CommonResult.class);

    }

    @GetMapping("/consumer/payment/postForEntity/create")
    public CommonResult<Payment> create2(Payment payment){
        return restTemplate.postForEntity(PAYMENT_URL + "/payment/create",payment,CommonResult.class).getBody();

    }

    @GetMapping("/consumer/payment/get/{id}")
    public CommonResult<Payment> getPayment(@PathVariable("id") Long id){
        return restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id,CommonResult.class);
    }

    @GetMapping("/consumer/payment/getForEntity/{id}")
    public CommonResult<Payment> getPayment2(@PathVariable("id") Long id) {
        ResponseEntity<CommonResult> entity = restTemplate.getForEntity(PAYMENT_URL+"/payment/get/"+id,CommonResult.class);

        if(entity.getStatusCode().is2xxSuccessful()){
            log.info(entity.getStatusCode()+"\t" + entity.getHeaders());
            return entity.getBody();
        }else{
            return new CommonResult<>(444,"操作失败");
        }
    }

    @GetMapping(value = "/consumer/payment/lb")
    public String getPaymentLB(){
        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");

        if(instances == null || instances.size() <= 0){
            return null;
        }

        ServiceInstance serviceInstance = loadBalancer.instances(instances);
        URI uri = serviceInstance.getUri();

        return restTemplate.getForObject(uri+"/payment/lb", String.class);
    }
}

测试

http://localhost/consumer/payment/lb