SpringCloud Ribbon 负载均衡的服务调用

Ribbon简介

实现负载均衡方式1：通过服务器端实现负载均衡(nginx)

()

实现负载均衡方式2：通过客户端实现负载均衡。

Ribbon是什么

Ribbon是Netflix发布的云中间层服务开源项目，其主要功能是提供客户端实现负载均衡算法。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，Ribbon是一个客户端负载均衡器，我们可以在配置文件中Load Balancer后面的所有机器，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。

下图展示了Eureka使用Ribbon时的大致架构：

创建一个user-service-8301模块

一，pom.xml需要添加的依赖：

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

二，application.yml的配置：

server:
  port: 8301
spring:
  application:
    name: user-service
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://replica1:8001/eureka/

三，在src目录下新建一些包，例如controller、domain、service

domain包下分别新建User类和CommonResult类

User类的代码：

package com.tiger.springcloud.domain;

public class User {
    private Long id;
    private String username;
    private String password;

    public User(){}

    public User(Long id, String username, String password){
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

CommonResult的代码：

package com.tiger.springcloud.domain;

public class CommonResult<T> {
    private T data;
    private String message;
    private Integer code;

    public CommonResult(){}

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

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

    public CommonResult(T data) {
        this(data, "操作成功", 200);
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }
}

service包下新建一个UserService接口和一个UserService实现类

UserService的代码：

package com.tiger.springcloud.service;

import com.tiger.springcloud.domain.User;

import java.util.List;

public interface UserService {
    void create(User user);

    User getUser(Long id);

    void update(User user);

    void delete(Long id);

    User getByUsername(String username);

    List<User> getUserByIds(List<Long> ids);
}

UserService实现类的代码:

package com.tiger.springcloud.service.impl;

import com.tiger.springcloud.domain.User;
import com.tiger.springcloud.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;

@Service
public class UserServiceImpl implements UserService {
    private List<User> userList;

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

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

    public void update(User user) {
        userList.stream().filter(userItem -> userItem.getId().equals(user.getId())).forEach(userItem -> {
            userItem.setUsername(user.getUsername());
            userItem.setPassword(user.getPassword());
        });
    }

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

    public User getByUsername(String username) {
        List<User> findUserList = userList.stream().filter(userItem -> userItem.getUsername().equals(username)).collect(Collectors.toList());
        if (!CollectionUtils.isEmpty(findUserList)) {
            return findUserList.get(0);
        }
        return null;
    }

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

    @PostConstruct
    public void initData() {
        userList = new ArrayList<>();
        userList.add(new User(1L, "tiger1_service1", "123456"));
        userList.add(new User(2L, "tiger2_service1", "123456"));
        userList.add(new User(3L, "tiger3_service1", "123456"));
    }
}

controller包下UserController的代码：

package com.tiger.springcloud.controller;


import com.tiger.springcloud.domain.CommonResult;
import com.tiger.springcloud.domain.User;
import com.tiger.springcloud.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;

@RestController
@RequestMapping("/user")
public class UserController {
    private Logger LOGGER = LoggerFactory.getLogger(this.getClass());

    @Autowired
    private UserService userService;

    @PostMapping("/create")
    public CommonResult create(@RequestBody User user) {
        userService.create(user);
        return new CommonResult("操作成功", 200);
    }

    @GetMapping("/{id}")
    public CommonResult<User> getUser(@PathVariable Long id) {
        User user = userService.getUser(id);
        LOGGER.info("根据id获取用户信息，用户名称为：{}",user.getUsername());
        return new CommonResult<>(user);
    }

    @GetMapping("/getUserByIds")
    public CommonResult<List<User>> getUserByIds(@RequestParam List<Long> ids) {
        List<User> userList= userService.getUserByIds(ids);
        LOGGER.info("根据ids获取用户信息，用户列表为：{}",userList);
        return new CommonResult<>(userList);
    }

    @GetMapping("/getByUsername")
    public CommonResult<User> getByUsername(@RequestParam String username) {
        User user = userService.getByUsername(username);
        return new CommonResult<>(user);
    }

    @PostMapping("/update")
    public CommonResult update(@RequestBody User user) {
        userService.update(user);
        return new CommonResult("操作成功", 200);
    }

    @PostMapping("/delete/{id}")
    public CommonResult delete(@PathVariable Long id) {
        userService.delete(id);
        return new CommonResult("操作成功", 200);
    }
}

启动类的代码：

package com.tiger.springcloud;

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

@EnableDiscoveryClient
@SpringBootApplication
public class UserServiceApplication8301 {
    public static void main(String[] args) {
        SpringApplication.run(UserServiceApplication8301.class, args);
    }
}

再创建一个user-service-8302模块

user-service-8302模块参考user-service-8301模块的依赖和配置。

user-service-8302的application.yam的配置：

server:
  port: 8302
spring:
  application:
    name: user-service
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://replica1:8001/eureka/

创建一个ribbon-service模块

一，pom.xml需要添加的依赖：

<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>

二，application.yml的配置：

server:
  port: 8303
spring:
  application:
    name: ribbon-service
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://replica1:8001/eureka/
service-url:
  user-service: http://user-service

注意：service-url.user-service指向的是user-service这个名字，也就是user-service-8301模块和user-service-8302模块的spring.application.name

三，src目录下相关的包有config,controller, domain

domain包下的User类和CommonResult类的代码跟user-service-8301模块和user-service-8302模块的User类和CommonResult类的代码一样。

config包下的RibbonConfig类的代码：

package com.springcloud.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;

@Configuration
public class RibbonConfig {

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }
}

controller包下的UserRibbonController代码：

package com.springcloud.ribbon.controller;

import com.springcloud.ribbon.domain.CommonResult;
import com.springcloud.ribbon.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;

@RestController
@RequestMapping("/user")
public class UserRibbonContoller {

    @Autowired
    private RestTemplate restTemplate;

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

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

    @GetMapping("/getByUsername")
    public CommonResult getByUsername(@RequestParam String username) {
        return restTemplate.getForObject(userServiceUrl + "/user/getByUsername?username={1}", CommonResult.class, username);
    }

    @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);
        }
    }

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

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

    @PostMapping("/delete/{id}")
    public CommonResult delete(@PathVariable Long id) {
        return restTemplate.postForObject(userServiceUrl + "/user/delete/{1}", null, CommonResult.class, id);
    }
}

结果演示

• 启动eureka-server-8001启动类
• 启动user-service-8301启动类
• 启动user-service-8302启动类
• 启动ribbon-service-8303启动类

访问http://replica1:8001，如下图所示：

访问http://replica1:8303/user/1

刷新或刷新几次http://replica1:8303/user/1的页面变化如下图所示：

Ribbon的常用配置

全局配置

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.RandomRule #修改负载均衡算法

指定服务进行配置

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

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.RandomRule #修改负载均衡算法

Ribbon的负载均衡策略

所谓的负载均衡策略，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的B实例，ribbon可以选择以下几种负载均衡策略。

• com.netflix.loadbalancer.RandomRule：从提供服务的实例中以随机的方式；
• 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；
• 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；
• 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；
• com.netflix.loadbalancer.BestAvailableRule：选择并发较小的实例；
• com.netflix.loadbalancer.AvailabilityFilteringRule：先过滤掉故障实例，再选择并发较小的实例；
• 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。

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，举例如下：

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

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，举例如下：

@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) {
    return restTemplate.postForObject(userServiceUrl + "/user/create", user, CommonResult.class);
}

postForEntity示例

@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);

PUT请求示例

@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);

DELETE请求示例

@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);
}

注意：以上内容学习于掘金博主MacroZheng

参考：

SpringCloud实战微服务之——Ribbon详解 https://blog.csdn.net/u013087513/article/details/79775306

Spring Cloud Ribbon：负载均衡的服务调用 https://juejin.im/post/5d7f9006f265da03951a260c#heading-22