Ribbon负载均衡器

andrew7676

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SpringCloud

SpringCloud

1. Ribbon简介

Ribbon是Netflix发布的负载均衡器，它有助于控制HTTP和TCP的客户端的行为。为Ribbon配置服务提供者地址后，Ribbon就可基于某种负载均衡算法，自动地帮助服务消费者去请求。Ribbon默认为我们提供了很多负载均衡算法，例如随机、轮询等。当然，我们也可为Ribbon实现自定义的负载均衡算法。

在SpringCloud中，当Ribbon与Eureka配合使用时，Ribbon可自动从EurekaServer获取服务提供者地址列表，并基于负载均衡算法，请求其中一个服务提供者实例。展示了Ribbon与Eureka配合使用时的架构。

使用Ribbon，结合eureka集群，来实现服务的调用。

2. Ribbon初步应用

2.1) 服务消费者microservice-student-consumer-80增加pom.xml依赖

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

2.2) 服务消费者microservice-student-consumer-80增加application.yml支持eureka

server:
  port: 80
  context-path: /
eureka:
  client:
    #false 由于注册中心的职责就是维护服务实例，它并不需要去检索服务，所以也设置为false
    register-with-eureka: false
    service-url: 
      defaultZone: http://eureka2001.andrew.com:2001/eureka/,http://eureka2002.andrew.com:2002/eureka/,http://eureka2003.andrew.com:2003/eureka/

2.3) 服务消费者microservice-student-consumer-80增加SpringCloudConfig.java注解@LoadBalanced

package com.andrew.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 SpringCloudConfig {
    @Bean
    @LoadBalanced // 引入ribbon负载均衡
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }
}

2.4) 服务消费者microservice-student-consumer-80增加StudentConsumerApplication_80.java注解@EnableEurekaClient

package com.andrew;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class, HibernateJpaAutoConfiguration.class })
@EnableEurekaClient
public class StudentConsumerApplication_80 {
    public static void main(String[] args) {
        SpringApplication.run(StudentConsumerApplication_80.class, args);
    }
}

2.5)服务消费者 microservice-student-consumer-80修改StudentConsumerController.java属性PRE_HOST

package com.andrew.controller;

import java.util.List;
import javax.annotation.Resource;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import com.andrew.entity.Student;

@RestController
@RequestMapping("/student")
public class StudentConsumerController {
    @Resource
    private RestTemplate restTemplate;
    
    // private final static String PRE_HOST="http://localhost:1001";
    private final static String PRE_HOST="http://MICROSERVICE-STUDENT";

    @PostMapping(value = "/save")
    private boolean save(Student student) {
        return restTemplate.postForObject(PRE_HOST+"/student/save", student, Boolean.class);
    }
    @SuppressWarnings("unchecked")
    @GetMapping(value = "/list")
    public List<Student> list() {
        return restTemplate.getForObject(PRE_HOST+"/student/list", List.class);
    }
    @GetMapping(value = "/get/{id}")
    public Student get(@PathVariable("id") Integer id) {
        return restTemplate.getForObject(PRE_HOST+"/student/get/" + id, Student.class);
    }

    @GetMapping(value = "/delete/{id}")
    public boolean delete(@PathVariable("id") Integer id) {
        try {
            restTemplate.getForObject(PRE_HOST+"/student/delete/" + id, Boolean.class);
            return true;
        } catch (Exception e) {
            return false;
        }
    }
}

2.6) 服务提供者microservice-student-provider-1001增加application.yml配置

spring:
  application: 
    name: microservice-student

启动microservice-eureka-server-2001
启动microservice-eureka-server-2002
启动microservice-eureka-server-2003
启动microservice-student-provider-1001
启动microservice-student-consumer-80

执行
http://localhost/student/list
[{"id":1,"name":"zhangsan","grade":"11"},{"id":2,"name":"lisi","grade":"12"},{"id":3,"name":"wangwu","grade":"13"},{"id":4,"name":"student04","grade":"14"},{"id":5,"name":null,"grade":null},{"id":6,"name":"student06","grade":"16"}]

3. Ribbon负载均衡

3.1) 新建两个module 服务提供者microservice-student-provider-1002 服务提供者microservice-student-provider-1003

new -> Maven Module
    -> create a simple project
Module Name:microservice-student-provider-1002
Parent Project:microservice
Working set:SpringCloud
    -> Artifact
Group Id:com.andrew.springcloud
Artifact Id:microservice-student-provider-1002
Version:0.0.1-SNAPSHOT
Packaging:jar

代码与microservice-student-provider-1001相同

new -> Maven Module
    -> create a simple project
Module Name:microservice-student-provider-1003
Parent Project:microservice
Working set:SpringCloud
    -> Artifact
Group Id:com.andrew.springcloud
Artifact Id:microservice-student-provider-1003
Version:0.0.1-SNAPSHOT
Packaging:jar

代码与microservice-student-provider-1001相同

3.2) 修改两个项目application.yml的server.port和客户端实例名称

server:
  port: 1002
  context-path: /
eureka:
  instance:
    instance-id: microservice-student:1002 #客户端实例名称

server:
  port: 1003
  context-path: /
eureka:
  instance:
    instance-id: microservice-student:1003 #客户端实例名称

3.3) 修改三个项目StudentProviderController.java增加调用区分代码

@GetMapping(value = "/list")
public List<Student> list() {
    System.out.println("list----------------------------------1001");
    return studentService.list();
}

@GetMapping(value = "/list")
public List<Student> list() {
    System.out.println("list----------------------------------1002");
    return studentService.list();
}

@GetMapping(value = "/list")
public List<Student> list() {
    System.out.println("list----------------------------------1003");
    return studentService.list();
}

启动microservice-eureka-server-2001
启动microservice-eureka-server-2002
启动microservice-eureka-server-2003
启动microservice-student-provider-1001
启动microservice-student-provider-1002
启动microservice-student-provider-1003

先测试服务提供者：
http://localhost:1001/student/list
http://localhost:1002/student/list
http://localhost:1003/student/list

再测试下eureka：
http://eureka2001.andrew.com:2001/
http://eureka2002.andrew.com:2002/
http://eureka2003.andrew.com:2003/

然后再启动服务消费者
microservice-student-consumer-80

http://localhost/student/list
list----------------------------------1001 - 1003随机调用

3.4) ribbon默认策略

这种默认的轮询策略肯定是不能满足实际需求的，比如有3个服务提供者，突然挂了一个，这样的话，默认轮询，总有1/3的概率访问失败； ribbon默认给我们提供的策略有哪些；

BestAvailableRule	public class BestAvailableRule extends ClientConfigEnabledRoundRobinRule	选择一个最小的并发请求的server	逐个考察Server，如果Server被tripped了，则忽略，在选择其中ActiveRequestsCount最小的server
AvailabilityFilteringRule	public class AvailabilityFilteringRule extends PredicateBasedRule	过滤掉那些因为一直连接失败的被标记为circuit tripped的后端server，并过滤掉那些高并发的的后端server（active connections 超过配置的阈值）	使用一个AvailabilityPredicate来包含过滤server的逻辑，其实就就是检查status里记录的各个server的运行状态
WeightedResponseTimeRule	public class WeightedResponseTimeRule extends RoundRobinRule	根据响应时间分配一个weight，响应时间越长，weight越小，被选中的可能性越低。	一个后台线程定期的从status里面读取评价响应时间，为每个server计算一个weight。Weight的计算也比较简单responsetime 减去每个server自己平均的responsetime是server的权重。当刚开始运行，没有形成status时，使用roubine策略选择server。
RetryRule	public class RetryRule extends AbstractLoadBalancerRule	对选定的负载均衡策略机上重试机制。	在一个配置时间段内当选择server不成功，则一直尝试使用subRule的方式选择一个可用的server
RoundRobinRule	public class RoundRobinRule extends AbstractLoadBalancerRule	roundRobin方式轮询选择server	轮询index，选择index对应位置的server
RandomRule	public class RandomRule extends AbstractLoadBalancerRule	随机选择一个server	在index上随机，选择index对应位置的server
ZoneAvoidanceRule	public class ZoneAvoidanceRule extends PredicateBasedRule	复合判断server所在区域的性能和server的可用性选择server	使用ZoneAvoidancePredicate和AvailabilityPredicate来判断是否选择某个server，前一个判断判定一个zone的运行性能是否可用，剔除不可用的zone（的所有server），AvailabilityPredicate用于过滤掉连接数过多的Server

3.5) 服务消费者microservice-student-consumer-80中配置轮询策略

package com.andrew.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;
import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RetryRule;

@Configuration
public class SpringCloudConfig {
    @Bean
    @LoadBalanced // 引入ribbon负载均衡，此处没有用
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }
    /**
     * 自定义轮询算法
     */
    @Bean
    public IRule myRule(){
        return new RetryRule();
    }
}

启动microservice-eureka-server-2001
启动microservice-eureka-server-2002
启动microservice-eureka-server-2003
启动microservice-student-provider-1001
启动microservice-student-provider-1002
启动microservice-student-provider-1003

先测试服务提供者：
http://localhost:1001/student/list
http://localhost:1002/student/list
http://localhost:1003/student/list

再测试下eureka：
http://eureka2001.andrew.com:2001/
http://eureka2002.andrew.com:2002/
http://eureka2003.andrew.com:2003/

然后再启动服务消费者
microservice-student-consumer-80

http://localhost/student/list
list----------------------------------1001 - 1003根据轮询原理调用

或者挂掉其中某个服务再调用