Spring Cloud Ribbon

Spring Cloud Ribbon:负载均衡的服务调用

---

前言

• 什么是Ribbon？

Spring Cloud Ribbon是一套实现客户端负载均衡的工具，注意是客户端，当然也有服务端的负载均衡工具，如Ngnix，可以认为Ribbon就是一个负载均衡(Load Balancer)。负载均衡就是将用户的请求平摊的分配到多个服务器，从而达到系统的高可用。

简单来说，Ribbon的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。

• 在微服务架构中，很多服务都会部署多个，其他服务去调用该服务的时候，如何保证负载均衡是个不得不去考虑的问题。负载均衡可以增加系统的可用性和扩展性，当我们使用RestTemplate来调用其他服务时，Ribbon可以很方便的实现负载均衡功能。

RestTemplate的使用

RestTemplate是一个HTTP客户端，使用它我们可以方便的调用HTTP接口，支持GET、POST、PUT、DELETE等方法。

GET请求方法

<T> T getForObject(String url, Class<T> responseType, Object... uriVariables);

<T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables);

<T> T getForObject(URI url, Class<T> responseType);

<T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables);

<T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables);

<T> ResponseEntity<T> getForEntity(URI var1, Class<T> responseType);

• getForObject方法

返回对象为响应体中数据转化成的对象，如下：

@GetMapping("/findByName/{userName}")
public CommonResult getByUserName(@PathVariable String userName) {
    return restTemplate.getForObject(userServiceUrl + "/user/findByName/{1}", CommonResult.class, userName);
}

• getForEntity方法

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、响应状态码、响应体等，如下：

@GetMapping("/getEntityByUsername")
public CommonResult getEntityByUsername(@RequestParam String username) {
    ResponseEntity<CommonResult> entity = restTemplate.getForEntity(userServiceUrl + "/user/getByUsername?username={1}", CommonResult.class, username);
    if (entity.getStatusCode().is2xxSuccessful()) {
        return entity.getBody();
    } else {
        return new CommonResult("操作失败", 500);
    }
}

POST请求方法

<T> T postForObject(String url, @Nullable Object request, Class<T> responseType, Object... uriVariables);

<T> T postForObject(String url, @Nullable Object request, Class<T> responseType, Map<String, ?> uriVariables);

<T> T postForObject(URI url, @Nullable Object request, Class<T> responseType);

<T> ResponseEntity<T> postForEntity(String url, @Nullable Object request, Class<T> responseType, Object... uriVariables);

<T> ResponseEntity<T> postForEntity(String url, @Nullable Object request, Class<T> responseType, Map<String, ?> uriVariables);

<T> ResponseEntity<T> postForEntity(URI url, @Nullable Object request, Class<T> responseType);

• postForObject示例

@PostMapping("/create")
public CommonResult create(@RequestBody User user) {
    restTemplate.postForObject(userServiceUrl + "/user/create", user, CommonResult.class);
    return new CommonResult(200, "操作成功");
}

• postForEntity

@PostMapping("/create")
public CommonResult create(@RequestBody User user) {
    return restTemplate.postForEntity(userServiceUrl + "/user/create", user, CommonResult.class).getBody();
}

PUT请求方法

void put(String url, @Nullable Object request, Object... uriVariables);

void put(String url, @Nullable Object request, Map<String, ?> uriVariables);

void put(URI url, @Nullable Object request);

示例

@PutMapping("/update")
public CommonResult update(@RequestBody User user) {
    restTemplate.put(userServiceUrl + "/user/update", user);
    return new CommonResult("操作成功",200);
}

DELETE请求方法

void delete(String url, Object... uriVariables);

void delete(String url, Map<String, ?> uriVariables);

void delete(URI url);

示例

@DeleteMapping("/delete/{id}")
public CommonResult delete(@PathVariable Long id) {
   restTemplate.delete(userServiceUrl + "/user/delete/{1}", null, id);
   return new CommonResult("操作成功",200);
}

正是开始Spring Cloud Ribbon的实战代码学习

user-service

首先创建一个user-service模块提供服务，用于给Ribbon调用

创建模块user-service，并在pom.xml中添加依赖

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

创建application.yml文件进行配置

作为Ribbon调用的服务端，主要配置了服务名、端口和注册中心地址

server:
  port: 8001    #端口

spring:
  application:
    name: user-service    #应用名，后面Ribbon调用可直接通过应用名调用
eureka:
  instance:
    hostname: localhost
  client:
    fetch-registry: true    #指定是否从注册中心获取服务列表
    register-with-eureka: true    #指定是否要注册到注册中心
    service-url:
      defaultZone: http://jamie:123456@localhost:8761/eureka/     #注册中心地址

创建UserController用于提供调用接口

UserController控制层类定义了对User对象常见的CRUD接口。

package com.jamieLove.controller;

import com.jamieLove.domain.CommonResult;
import com.jamieLove.domain.User;
import com.jamieLove.service.UserService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

/**
 * @Author:JamieLove
 * @Date:2019-12-10 13:42
 * @Description:
 */
@RestController
@RequestMapping("/user")
public class UserController {
    private static Logger LOGGER = LoggerFactory.getLogger(UserController.class);

    @Autowired
    private UserService userService;

    @PostMapping("/create")
    public CommonResult create(@RequestBody User user) {
        userService.create(user);
        LOGGER.info("新增用户:{}", user);
        return new CommonResult(200, "新增成功");
    }

    @GetMapping("/all")
    public CommonResult getAllUserList() {
        List<User> userLists = userService.getAllUserList();
        LOGGER.info("查询所有 的用户列表:{}", userLists);
        return new CommonResult(200, "查询成功", userLists);
    }

    @GetMapping("/getUser/{id}")
    public CommonResult getUser(@PathVariable Long id) {
        User user = userService.getUser(id);
        LOGGER.info("通过id:{}查询用户信息:", id);
        return new CommonResult(200, "操作成功", user);
    }

    @PostMapping("/update")
    public CommonResult update(@RequestBody User user) {
        userService.update(user);
        LOGGER.info("更新用户信息:{}", user);
        return new CommonResult(200, "更新成功");
    }

    @GetMapping("/delete/{id}")
    public CommonResult delete(@PathVariable Long id) {
        userService.delete(id);
        LOGGER.info("根据id:{}删除用户信息", id);
        return new CommonResult(200, "删除成功");
    }

    @GetMapping("/findByName/{userName}")
    public CommonResult findByName(@PathVariable String userName) {
        User user = userService.getUserByName(userName);
        LOGGER.info("根据用户名:{}查询用户信息", userName);
        return new CommonResult(200, "查询成功", user);
    }

    @PostMapping("/getUserList")
    public CommonResult getUserList(@RequestBody List<Long> ids) {
        List<User> userList = userService.getUserList(ids);
        LOGGER.info("根据id集合:{}查询用户列表:{}", ids, userList);
        return new CommonResult(200, "查询成功", userList);
    }
}

创建User实体类和结果返回对象封装类

package com.jamieLove.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

/**
 * @Author:JamieLove
 * @Date:2019-12-10 12:48
 * @Description:
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User implements Serializable {
    private static final long serialVersionUID = 9085447891383824313L;

    private Long id;

    private String userName;

    private String passWord;
}

package com.jamieLove.domain;

import lombok.Data;

/**
 * @Author:JamieLove
 * @Date:2019-12-10 12:51
 * @Description:
 */
@Data
public class CommonResult<T> {

    private Integer code;

    private String message;

    private T data;

    public CommonResult() {
    }

    public CommonResult(Integer code, String message, T data) {
        this.code = code;
        this.message = message;
        this.data = data;
    }

    public CommonResult(Integer code, String message) {
        this.code = code;
        this.message = message;
    }

    public CommonResult(T data) {
        this.data = data;
    }
}

创建User对象CRUD的service类

接口类：

package com.jamieLove.service;

import com.jamieLove.domain.User;

import java.util.List;

/**
 * @Author:JamieLove
 * @Date:2019-12-10 12:55
 * @Description:
 */
public interface UserService {

    void create(User user);

    User getUser(Long id);

    void update(User user);

    void delete(Long id);

    User getUserByName(String userName);

    List<User> getUserList(List<Long> ids);

    List<User> getAllUserList();
}

接口实现类：

package com.jamieLove.service.impl;

import com.jamieLove.domain.User;
import com.jamieLove.service.UserService;
import org.springframework.stereotype.Service;
import org.springframework.util.CollectionUtils;

import javax.annotation.PostConstruct;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

/**
 * @Author:JamieLove
 * @Date:2019-12-10 12:58
 * @Description:
 */
@Service
public class UserServiceImpl implements UserService {

    private List<User> userList;

    @Override
    public void create(User user) {
        userList.add(user);
    }

    @Override
    public User getUser(Long id) {
        List<User> findUserList = userList.stream().filter(userList -> userList.getId().equals(id)).collect(Collectors.toList());
        if (!CollectionUtils.isEmpty(findUserList)) {
            return findUserList.get(0);
        }
        return null;
    }

    @Override
    public void update(User user) {
        userList.stream().filter(userItem -> userItem.getId().equals(user.getId())).forEach(userItem -> {
            userItem.setUserName(user.getUserName());
            userItem.setPassWord(user.getPassWord());
        });
    }

    @Override
    public void delete(Long id) {
        User user = getUser(id);
        if (user != null) {
            userList.remove(user);
        }
    }

    @Override
    public User getUserByName(String userName) {
        List<User> findList = userList.stream().filter(userItem -> userItem.getUserName().equals(userName)).collect(Collectors.toList());
        if (!CollectionUtils.isEmpty(findList)) {
            return findList.get(0);
        }
        return null;
    }

    @Override
    public List<User> getUserList(List<Long> ids) {
        List<User> findUserList = userList.stream().filter(userItem -> ids.contains(userItem.getId())).collect(Collectors.toList());
        return findUserList;
    }

    @Override
    public List<User> getAllUserList() {
        return userList;
    }

    @PostConstruct
    public void initUser() {
        userList = new ArrayList<>();
        userList.add(new User(1L, "张三", "123456"));
        userList.add(new User(2L, "李四", "223456"));
        userList.add(new User(3L, "王五", "323456"));
    }
}

ribbon-service

创建ribbon-service模块来调用user-service模块实现负载均衡的服务调用。

创建模块ribbon-service，并在pom.xml中添加相关依赖

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

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

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

创建application.yml配置文件进行配置

这里主要配置端口、应用名、注册中心地址、user-service的调用路径(通过应用名调用)以及ribbon相关的配置。

server:
  port: 8003
spring:
  application:
    name: ribbon-service
eureka:
  instance:
    hostname: localhost
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://jamie:123456@localhost:8761/eureka/

serice-url:
  user-service: http://user-service

user-service:
  ribbon:
    ConnectTimeout: 1000 #服务请求连接超时时间（毫秒）
    ReadTimeout: 3000 #服务请求处理超时时间（毫秒）
    OkToRetryOnAllOperations: true #对超时请求启用重试机制
    MaxAutoRetriesNextServer: 1 #切换重试实例的最大个数
    MaxAutoRetries: 1 # 切换实例后重试最大次数
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RoundRobinRule
#    com.netflix.loadbalancer.RandomRule #修改负载均衡算法

使用@LoadBalanced注解可以赋予RestTemplate负载均衡的能力

package com.jamieLove.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;
/**
 * @Author:JamieLove
 * @Date:2019-12-10 18:34
 * @Description:
 */
@Configuration
public class RibbonConfig {

    @Bean
    @LoadBalanced   //赋予了restTemplate具有负载均衡的能力
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

创建ribbon-service的控制层类

package com.jamieLove.controller;

import com.jamieLove.domain.CommonResult;
import com.jamieLove.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;

/**
 * @Author:JamieLove
 * @Date:2019-12-10 18:36
 * @Description:
 */
@RestController
@RequestMapping("/user")
public class RibbonServiceController {

    @Autowired
    private RestTemplate restTemplate;

    @Value("${serice-url.user-service}")
    private String userServiceUrl;

    @RequestMapping("/all")
    public CommonResult getAllUserList() {
        return restTemplate.getForObject(userServiceUrl + "/user/all", CommonResult.class);
    }

    @PostMapping("/create")
    public CommonResult create(@RequestBody User user) {
        restTemplate.postForObject(userServiceUrl + "/user/create", user, CommonResult.class);
        return new CommonResult(200, "操作成功");
    }

    @GetMapping("/getUser/{id}")
    public CommonResult getUser(@PathVariable Long id) {
        return restTemplate.getForObject(userServiceUrl + "/user/getUser/{1}", CommonResult.class, id);
    }

    @GetMapping("/findByName/{userName}")
    public CommonResult getByUserName(@PathVariable String userName) {
        return restTemplate.getForObject(userServiceUrl + "/user/findByName/{1}", CommonResult.class, userName);
    }
}

启动类

package com.jamieLove;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

/**
 * @Author:JamieLove
 * @Date:2019-12-10 18:30
 *
 * @Description:
 */
@SpringBootApplication
@EnableDiscoveryClient
public class RibbonServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(RibbonServiceApplication.class, args);
    }
}

负载均衡功能演示

• 启动eureka-server:8761
• 启动user-service:8001
• 启动user-service:8002，可以通过修改IDEA中SpringBoot的启动配置实现：

• 启动ribbon-service:8003

注：以上服务启动成功，可在http://localhost:8761/eureka/有如下显示：

• 可通过网页或者postman工具调用接口进行测试:http://localhost:8003/user/all

可以发现运行在8001和8002的user-service控制台交替打印如下信息：

可以通过修改ribbon的配置，改变负载均衡策略选择实例。

user-service:
  ribbon:
    ConnectTimeout: 1000 #服务请求连接超时时间（毫秒）
    ReadTimeout: 3000 #服务请求处理超时时间（毫秒）
    OkToRetryOnAllOperations: true #对超时请求启用重试机制
    MaxAutoRetriesNextServer: 1 #切换重试实例的最大个数
    MaxAutoRetries: 1 # 切换实例后重试最大次数
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RoundRobinRule
#    com.netflix.loadbalancer.RandomRule #修改负载均衡算法

与全局配置的区别就是ribbon节点挂在服务名称下面，如上就是对ribbon-service调用user-service时的单独配置

Ribbon的负载均衡策略

所谓负载均衡策略，就是当A服务调用B服务时，此时B服务有多个实例，这时A服务以何种方式来选择调用B服务的实例，Ribbon可以选择以下几种负载均衡策略。

1. com.netflix.loadbalancer.RandomRule：从提供服务的实例中以随机的方式；
2. com.netflix.loadbalancer.RoundRobinRule：以线性轮询的方式，就是维护一个计数器，从提供服务的实例中按顺序选取，第一次选第一个，第二次选第二个，以此类推，到最后一个以后再从头来过；
3. com.netflix.loadbalancer.RetryRule：在RoundRobinRule的基础上添加重试机制，即在指定的重试时间内，反复使用线性轮询策略来选择可用实例；
4. com.netflix.loadbalancer.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；
5. com.netflix.loadbalancer.BestAvailableRule：选择并发较小的实例；
6. com.netflix.loadbalancer.AvailabilityFilteringRule：先过滤掉故障实例，再选择并发较小的实例；
7. com.netflix.loadbalancer.ZoneAwareLoadBalancer：采用双重过滤，同时过滤不是同一区域的实例和故障实例，选择并发较小的实例。