Spring Cloud学习笔记-Ribbon 源码分析

利用 RibbonLoadBalancerClient

新建一个工程

三个模块：

• user-api：公用 API
• user-robbon-client：客户端应用
• user-service-provider：服务端应用

实现 user-robbon-client

配置信息

application.properties:

## 用户 Ribbon 客户端应用
spring.application.name = user-ribbon-client

## 服务端口
server.port = 8080

## 提供方服务名称
provider.service.name = user-service-provider
## 提供方服务主机
provider.service.host = localhost
## 提供方服务端口
provider.service.port = 9090

## 关闭 Eureka Client，显示地通过配置方式注册 Ribbon 服务地址
eureka.client.enabled = false

## 定义 user-service-provider Ribbon 的服务器地址
## 为 RibbonLoadBalancerClient 提供服务列表
user-service-provider.ribbon.listOfServers = \
  http://${provider.service.host}:${provider.service.port}

编写客户端调用

package com.segumentfault.spring.cloud.lesson7.user.ribbon.client.web.controller;

import com.segumentfault.spring.cloud.lesson7.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import javax.ws.rs.GET;
import java.io.IOException;

/**
 * 用户 Ribbon Controller
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since 0.0.1
 */
@RestController
public class UserRibbonController {

    /**
     * 负载均衡器客户端
     */
    @Autowired
    private LoadBalancerClient loadBalancerClient;

    @Value("${provider.service.name}")
    private String providerServiceName;


    @GetMapping("")
    public String index() throws IOException {

        User user = new User();
        user.setId(1L);
        user.setName("小马哥");

        // 选择指定的 service Id
        ServiceInstance serviceInstance = loadBalancerClient.choose(providerServiceName);

        return loadBalancerClient.execute(providerServiceName, serviceInstance, instance -> {

            //服务器实例，获取 主机名（IP） 和 端口
            String host = instance.getHost();
            int port = instance.getPort();
            String url = "http://" + host + ":" + port + "/user/save";
            RestTemplate restTemplate = new RestTemplate();

            return restTemplate.postForObject(url, user, String.class);

        });

    }

}

编写引导类

package com.segumentfault.spring.cloud.lesson7.user.ribbon.client;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.ribbon.RibbonClient;

/**
 * 引导类
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since 0.0.1
 */
@SpringBootApplication
@RibbonClient("user-service-provider") // 指定目标应用名称
public class UserRibbonClientApplication {

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

实现 user-service-provider

配置信息

application.properties:

## 用户服务提供方应用信息
spring.application.name = user-service-provider

## 服务端口
server.port = 9090

## 关闭 Eureka Client，显示地通过配置方式注册 Ribbon 服务地址
eureka.client.enabled = false

实现 UserService

package com.segumentfault.spring.cloud.lesson7.user.service.provider.service;

import com.segumentfault.spring.cloud.lesson7.api.UserService;
import com.segumentfault.spring.cloud.lesson7.domain.User;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 内存实现{@link UserService}
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since 0.0.1
 */
@Service
public class InMemoryUserService implements UserService {

    private Map<Long, User> repository = new ConcurrentHashMap<>();

    @Override
    public boolean saveUser(User user) {
        return repository.put(user.getId(), user) == null;
    }

    @Override
    public List<User> findAll() {
        return new ArrayList(repository.values());
    }
}

实现 Web 服务

package com.segumentfault.spring.cloud.lesson7.user.service.web.controller;

import com.segumentfault.spring.cloud.lesson7.api.UserService;
import com.segumentfault.spring.cloud.lesson7.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

/**
 * 用户服务提供方 Controller
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since 0.0.1
 */
@RestController
public class UserServiceProviderController {

    @Autowired
    private UserService userService;

    @PostMapping("/user/save")
    public boolean user(@RequestBody User user){
        return userService.saveUser(user);
    }

}

编写引导类

package com.segumentfault.spring.cloud.lesson7.user.service;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.ribbon.RibbonClient;

/**
 * 引导类
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since 0.0.1
 */
@SpringBootApplication
public class UserServiceProviderApplication {

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

分析调用链路

选择服务器逻辑

LoadBalancerClient（LoadBalancerClient） -> ILoadBalancer（ZoneAwareLoadBalancer） -> IRule (ZoneAvoidanceRule)

自定义实现 IRule

扩展 AbstractLoadBalancerRule ： MyRule

package com.segumentfault.spring.cloud.lesson7.user.ribbon.client.rule;

import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.ILoadBalancer;
import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.Server;

import java.util.List;

/**
 * 自定义{@link IRule} 实现，永远选择最后一台可达服务器
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since 0.0.1
 */
public class MyRule extends AbstractLoadBalancerRule {

    @Override
    public void initWithNiwsConfig(IClientConfig clientConfig) {

    }

    @Override
    public Server choose(Object key) {

        ILoadBalancer loadBalancer = getLoadBalancer();

        //获取所有可达服务器列表
        List<Server> servers = loadBalancer.getReachableServers();
        if (servers.isEmpty()) {
            return null;
        }

        // 永远选择最后一台可达服务器
        Server targetServer = servers.get(servers.size() - 1);
        return targetServer;
    }

}

将 MyRule 暴露成 Bean

通过RibbonClientConfiguration学习源码：

@Bean
@ConditionalOnMissingBean
public IRule ribbonRule(IClientConfig config) {
   if (this.propertiesFactory.isSet(IRule.class, name)) {
      return this.propertiesFactory.get(IRule.class, config, name);
   }
   ZoneAvoidanceRule rule = new ZoneAvoidanceRule();
   rule.initWithNiwsConfig(config);
   return rule;
}

/**
 * 将 {@link MyRule} 暴露成 {@link Bean}
 *
 * @return {@link MyRule}
 */
@Bean
public IRule myRule() {
    return new MyRule();
}

配置化实现组件

通过学习PropertiesFactory 源码：

  public PropertiesFactory() {
      classToProperty.put(ILoadBalancer.class, "NFLoadBalancerClassName");
      classToProperty.put(IPing.class, "NFLoadBalancerPingClassName");
      classToProperty.put(IRule.class, "NFLoadBalancerRuleClassName");
      classToProperty.put(ServerList.class, "NIWSServerListClassName");
      classToProperty.put(ServerListFilter.class, "NIWSServerListFilterClassName");
  }

可知NFLoadBalancerClassName 等是可以配置的

实现 IPing : MyPing

package com.segumentfault.spring.cloud.lesson7.user.ribbon.client.ping;

import com.netflix.loadbalancer.IPing;
import com.netflix.loadbalancer.Server;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.util.UriComponentsBuilder;

import java.net.URI;

/**
 * 实现 {@link IPing} 接口：检查对象 /health 是否正常状态码:200
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since 0.0.1
 */
public class MyPing implements IPing {

    @Override
    public boolean isAlive(Server server) {

        String host = server.getHost();
        int port = server.getPort();
        // /health endpoint
        // 通过 Spring 组件来实现URL 拼装
        UriComponentsBuilder builder = UriComponentsBuilder.newInstance();
        builder.scheme("http");
        builder.host(host);
        builder.port(port);
        builder.path("/health");
        URI uri = builder.build().toUri();

        RestTemplate restTemplate = new RestTemplate();

        ResponseEntity responseEntity = restTemplate.getForEntity(uri, String.class);
        // 当响应状态等于 200 时，返回 true ，否则 false
        return HttpStatus.OK.equals(responseEntity.getStatusCode());
    }
    
}

增加配置

application.properties:

## 扩展 IPing 实现
user-service-provider.ribbon.NFLoadBalancerPingClassName = \
  com.segumentfault.spring.cloud.lesson7.user.ribbon.client.ping.MyPing