springcloud之Ribbon负载均衡及Feign消费者调用服务

微服务调用Ribbon

简介
这里要用到Ribbon，结合eureka，来实现服务的调用；

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，例如轮询、随机等。当然，我们也可为Ribbon实现自定义的负载均衡算法。
在Spring Cloud中，当Ribbon与Eureka配合使用时，Ribbon可自动从Eureka Server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。

应用
Ribbon是客户端负载均衡，所以肯定集成再消费端，也就是consumer端
我们修改microservice-student-consumer-80
首先，引入依赖，pom.xml 加入 ribbon相关依赖

<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-eurekaartifactId>
dependency>
<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-ribbonartifactId>
dependency>
<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-configartifactId>
dependency>

application.yml

server:
  port: 80
  context-path: /
eureka:
  client:
    service-url:
      defaultZone: http://eureka2001.zh.com:2001/eureka/,http://eureka2002.zh.com:2002/eureka/,http://eureka2003.zh.com:2003/eureka/
    register-with-eureka: false

ribbon结合eureka来调用服务提供者；

SpringCloudConfig也改成 要加个负载均衡配置 @LoadBalanced

因为和eureka整合，所以启动类StudentConsumerApplication_80 加个注解 @EnableEurekaClient

这里还有一个，要修改下StudentConsumerController的PRE_HOST，改成指定的微服务应用名称；
我们的微服务应用名称是 microservice-student
所以服务调用者这边的控制器里PRE_HOST改成 http://MICROSERVICE-STUDENT即可；
MICROSERVICE-STUDENT为Eureka注册中心的应用名称

当然这里要先在服务提供者microservice-student-provider-1001的application.yml加下配置，指定下应用名称：

application:
    name: microservice-student

配置好后，我们可以测试下；
先启动三个eureka，然后再启动服务提供者，再启动服务消费者；

结果就出来了，说明配置OK；

Ribbon负载均衡

按照它microservice-student-provider-1001建立一个microservice-student-provider子项目，然后将microservice-student-provider-1001这个子项目干掉；

前面搭建了初步例子，但是还没实现真正负载均衡，我们这里要先搞三个服务提供者集群，然后才能演示负载均衡，以及负载均衡策略；

新建项目microservice-student-provider-1002，microservice-student-provider-1003
pom.xml，application.yml，以及java类都复制一份，启动类名称对应的改下；
yml配置文件有两处要对应的改下，port端口改下，以及服务实例名称改下；

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>com.zhgroupId>
        <artifactId>springcloudartifactId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <artifactId>microservice-student-providerartifactId>

    <properties>
        <java.version>1.8java.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>com.zhgroupId>
            <artifactId>microservice-commonartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-data-jpaartifactId>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-tomcatartifactId>
        dependency>
        <dependency>
            <groupId>com.alibabagroupId>
            <artifactId>druid-spring-boot-starterartifactId>
        dependency>
        <dependency>
            <groupId>com.zhgroupId>
            <artifactId>microservice-commonartifactId>
            <version>1.0-SNAPSHOTversion>
            <scope>compilescope>
        dependency>

        
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-eurekaartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-configartifactId>
        dependency>
        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-actuatorartifactId>
        dependency>
    dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>

project>

启动类:

package com.zh.microservicestudentprovider;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@EntityScan("com.zh.*.*")
@EnableEurekaClient
@SpringBootApplication
public class MicroserviceStudentProviderApplication {

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

}

yml:

---
server:
  port: 1001
  context-path: /
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8
    username: root
    password: 123
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
  application:
    name: microservice-student
  profiles: provider-1001

eureka:
  instance:
    hostname: localhost
    appname: microservice-student
    instance-id: microservice-student:1001
    prefer-ip-address: true
  client:
    service-url:
      defaultZone: http://eureka2001.zh.com:2001/eureka/,http://eureka2002.zh.com:2002/eureka/,http://eureka2003.zh.com:2003/eureka/

info:
  groupId: com.zh.springcloud
  artifactId: microservice-student-provider-1001
  version: 1.0-SNAPSHOT
  userName: http://zh.com
  phone: 123456

---
server:
  port: 1002
  context-path: /
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8
    username: toot
    password: 123
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
  application:
    name: microservice-student
  profiles: provider-1002

eureka:
  instance:
    hostname: localhost
    appname: microservice-student
    instance-id: microservice-student:1002
    prefer-ip-address: true
  client:
    service-url:
      defaultZone: http://eureka2001.zh.com:2001/eureka/,http://eureka2002.zh.com:2002/eureka/,http://eureka2003.zh.com:2003/eureka/

info:
  groupId: com.zh.springcloud
  artifactId: microservice-student-provider-1002
  version: 1.0-SNAPSHOT
  userName: http://zh.com
  phone: 123456

---
server:
  port: 1003
  context-path: /
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8
    username: root
    password: 123
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
  application:
    name: microservice-student
  profiles: provider-1003

eureka:
  instance:
    hostname: localhost
    appname: microservice-student
    instance-id: microservice-student:1003
    prefer-ip-address: true
  client:
    service-url:
      defaultZone: http://eureka2001.zh.com:2001/eureka/,http://eureka2002.zh.com:2002/eureka/,http://eureka2003.zh.com:2003/eureka/

info:
  groupId: com.zh.springcloud
  artifactId: microservice-student-provider-1003
  version: 1.0-SNAPSHOT
  userName: http://zh.com
  phone: 123456

StudentProviderController.java

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

@RequestMapping("/ribbon")
public String ribbon(){
    return "工号【"+port+"】正在为您服务";
}

StudentConsumerController.java

@RequestMapping("/ribbon")
public String ribbon(){
    return restTemplate.getForObject(SERVER_IP_PORT + "/student/ribbon", String.class);
}

测试
有这种的话，就说明没问题

然后再启动服务消费者：
http://localhost/student/ribbon 多刷新几次 看控制台，我们看到 有默认的轮询策略，访问对应的服务提供者；

但是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； 所以我们看下ribbon默认给我们提供的策略有哪些；

策略名	策略声明	策略描述	实现说明
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。
RetryRulepublic 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。

服务消费端 SpringCloudConfig配置类
这里用了RetryRule,各位可以使用别的

 /**
     * 自定义轮询算法
     * @return
     */
    @Bean
    public IRule myRule(){
        return new RetryRule();
    }

解决问题

Feign简介及应用

简介
Feign是一个声明式的Web Service客户端，它使得编写Web Serivce客户端变得更加简单。我们只需要使用Feign来创建一个接口并用注解来配置它既可完成。它具备可插拔的注解支持，包括Feign注解和JAX-RS注解。Feign也支持可插拔的编码器和解码器。Spring Cloud为Feign增加了对Spring MVC注解的支持，还整合了Ribbon和Eureka来提供均衡负载的HTTP客户端实现。
应用
1、在common项目里建一个service（实际项目肯定是多个service）作为Feign客户端，用Feign客户端来调用服务器提供者，当然可以配置负载均衡；Feign客户端定义的目的，就是为了方便给其他项目调用；
修改 microservice-common
pom.xml引入Feign依赖：

<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-feignartifactId>
dependency>

我们定义了 FeignClient，同时指定了调用的服务名称MICROSERVICE-STUDENT
common项目修改后，maven clean下 然后install下；
建StudentClientService接口；

package com.zh.microservicecommon.service;

import com.zh.microservicecommon.entity.Student;
import org.springframework.cloud.netflix.feign.FeignClient;
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 java.util.List;

/**
 * Student Feign接口客户端
 * @author Administrator
 *
 */
@FeignClient(value="MICROSERVICE-STUDENT")
public interface StudentClientService {
 
    /**
     * 根据id查询学生信息
     * @param id
     * @return
     */
    @GetMapping(value="/student/get/{id}")
    public Student get(@PathVariable("id") Integer id);
     
    /**
     * 查询学生信息
     * @return
     */
    @GetMapping(value="/student/list")
    public List<Student> list();
     
    /**
     * 添加或者修改学生信息
     * @param student
     * @return
     */
    @PostMapping(value="/student/save")
    public boolean save(Student student);
     
    /**
     * 根据id删除学生信息
     * @return
     */
    @GetMapping(value="/student/delete/{id}")
    public boolean delete(@PathVariable("id") Integer id);

    @RequestMapping("/student/ribbon")
    public String ribbon();
}

2、新建一个Feign消费者项目；
参考microservice-student-consumer-80建一个microservice-student-consumer-feign-80
代码都复制一份，包括pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>com.zhgroupId>
        <artifactId>springcloudartifactId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <artifactId>microservice-student-consumer-feign-80artifactId>

    <properties>
        <java.version>1.8java.version>
    properties>
    <dependencies>
        <dependency>
            <groupId>com.zhgroupId>
            <artifactId>microservice-commonartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-data-jpaartifactId>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-tomcatartifactId>
        dependency>
        
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>springloadedartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-devtoolsartifactId>
        dependency>

        
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-eurekaartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-ribbonartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-configartifactId>
        dependency>

        
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-feignartifactId>
        dependency>
    dependencies>


    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>

project>

3、修改启动类名称，和加注解
启动类名称改下，改成StudentConsumerFeignApplication_80，同时加个注解@EnableFeignClients支持下Feign；

package com.zh.microservicestudentconsumerfeign80;

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;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

@EnableEurekaClient
@EnableFeignClients(value = "com.zh.*.*")
@SpringBootApplication(exclude={DataSourceAutoConfiguration.class, HibernateJpaAutoConfiguration.class})
public class MicroserviceStudentConsumerFeign80Application {

    public static void main(String[] args) {
        SpringApplication.run(MicroserviceStudentConsumerFeign80Application.class, args);
    }

}

因为现在用Fiegn，所以把restTemplate去掉，改成注入service，调用service方法来实现服务的调用；

package com.zh.microservicestudentconsumerfeign80.controller;

import com.zh.microservicecommon.entity.Student;
import com.zh.microservicecommon.service.StudentClientService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;

import java.util.List;

@RestController
@RequestMapping("/student")
public class StudentConsumerController {

    @Autowired
    private StudentClientService studentClientService;

    @Autowired
    private RestTemplate restTemplate;

    @PostMapping(value = "/save")
    private boolean save(Student student) {
        return studentClientService.save(student);
    }

    @GetMapping(value = "/list")
    public List<Student> list() {
        return studentClientService.list();
    }

    @GetMapping(value = "/get/{id}")
    public Student get(@PathVariable("id") Integer id) {
        return studentClientService.get(id);
    }

    @GetMapping(value = "/delete/{id}")
    public boolean delete(@PathVariable("id") Integer id) {
        try {
            studentClientService.delete(id);
            return true;
        } catch (Exception e) {
            return false;
        }
    }

    @RequestMapping("/ribbon")
    public String ribbon(){
        return studentClientService.ribbon();
    }
}

5、测试负载均衡；
SpringCloudConfig类的myRule，各位自行修改测试即可；