微服务之间的调用(Ribbon与Feign)

概述

在前面的文章中,我们讲了使用Eureka作为服务注册中心,在服务启动后,各个微服务会将自己注册到Eureka server。那么服务之间是如何调用?又是如何进行负载均衡的呢?本文讲讲服务之间调用及负载均衡Ribbon。

目前,在Spring cloud 中服务之间通过restful方式调用有两种方式

  • restTemplate+Ribbon
  • feign

从实践上看,采用feign的方式更优雅(feign内部也使用了ribbon做负载均衡)。

本文使用如下的项目实例来分别演示这两种写法。

  • hello服务,读取数据库,返回信息
  • world服务,返回信息
  • helloworld服务,调用了hello服务和world服务(restTemplate+Ribbon方式)
  • helloworldfeign服务,调用了hello服务和world服务(feign方式)
项目之间关系.png

本文项目代码:springcloud-demo
如何理解客户端Ribbon
zuul也有负载均衡的功能,它是针对外部请求做负载,那客户端ribbon的负载均衡又是怎么一回事?

客户端ribbon的负载均衡,解决的是服务发起方(在Eureka注册的服务)对被调用的服务的负载,比如我们查询商品服务要调用显示库存和商品明细服务,通过商品服务的接口将两个服务组合,可以减少外部应用的请求,比如手机App发起一次请求即可,可以节省网络带宽,也更省电。

ribbon是对服务之间调用做负载,是服务之间的负载均衡,zuul是可以对外部请求做负载均衡。


Ribbon负载均衡.png

hello服务与world服务

hello服务
Git项目代码:hello
pom.xml

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>        
        <!--connect the db-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <version>1.5.4.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.31</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
            <version>1.5.6.RELEASE</version>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR2</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

启动类HelloApplication:

package com.example.hello;

import com.example.hello.model.Info;
import com.example.hello.repository.InfoRepository;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.context.annotation.Bean;


@EnableDiscoveryClient
@SpringBootApplication
public class HelloApplication {

    private static final Logger log= LoggerFactory.getLogger(HelloApplication.class);
    public static final String KEY="Database";
    public static final String VALUE="MYSQL FROM BILLJIANG";

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

    @Bean
    public CommandLineRunner initDatabase(InfoRepository repository){
        return (args) -> {
            repository.save(new Info(KEY,VALUE));
        };
    }
}


入口类HelloController:

package com.example.hello.controller;

import com.example.hello.HelloApplication;
import com.example.hello.model.HelloMessage;
import com.example.hello.model.Info;
import com.example.hello.repository.InfoRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;


@RestController
public class HelloController {

    @Autowired
    private DiscoveryClient discoveryClient;

    @Autowired
    private InfoRepository infoRepository;

    @GetMapping("/")
    public String home(){
        return "hello";
    }

    @GetMapping("/message")
    public HelloMessage getMessage() {
        HelloMessage helloMessage = new HelloMessage();
        helloMessage.setName(getLocalInstanceInfo());
        helloMessage.setMessage(getInfoFromDatabase());
        return helloMessage;
    }


    private String getLocalInstanceInfo() {
        ServiceInstance serviceInstance = discoveryClient.getLocalServiceInstance();
        return serviceInstance.getServiceId() + ":" + serviceInstance.getHost() + ":" + serviceInstance.getPort();
    }


    private String getInfoFromDatabase() {
        List<Info> infoList = infoRepository.findByName(HelloApplication.KEY);
        for (Info info : infoList) {
            return info.toString();
        }
        return "(no database info)";
    }
}

配置文件application.yml:


#随机端口
server:
  port: 0

#服务注册中心
eureka:
  client:
    service-url:
      default-zone: http://localhost:8761/eureka
  instance:
    instance-id: ${spring.application.name}:${spring.application.instance_id:${random.value}}

#数据源
spring:
  application:
    name: hello
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/${{MYSQL_DATABASE}:foodb}
    username: ${{MYSQL_USERNAME}:root}
    password: ${{MYSQL_PASSWORD}:billjiang}
    testWhileIdle: true
    validationQuery: SELECT 1
  jpa:
    show-sql: true
    hibernate:
      ddl-auto: update
      naming-strategy: org.hibernate.cfg.ImprovedNamingStrategy
      properties:
        hibernate:
        dialect: org.hibernate.dialect.MySQL5Dialect
  zipkin:
    base-url: http://127.0.0.1:9411

其他类略,请参照源码:

world
world服务与hello服务类似,不过没有连接数据库
项目代码:world

helloworld调用hello服务和world服务

采用restTemplate+Ribbon调用服务。
项目代码:helloworld

启动类HelloworldApplication:
配置restTemplate的Bean

package com.example.helloworld;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
public class HelloworldApplication {

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

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

入口类HelloworldController:

package com.example.helloworld.controller;

import com.example.helloworld.model.HelloMessage;
import com.example.helloworld.model.HelloworldMessage;
import com.example.helloworld.model.WorldMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * @author billjiang 475572229@qq.com
 * @create 17-8-22
 */
@RestController
public class HelloworldController {

    private static final Logger log = LoggerFactory.getLogger(HelloworldController.class);

    private static final String HELLO_SERVICE_NAME = "hello";

    private static final String WORLD_SERVICE_NAME = "world";

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/")
    public String home() {
        return "hello world";
    }

    @GetMapping("/message")
    public HelloworldMessage getMessage() {
        HelloMessage hello = getMessageFromHelloService();
        WorldMessage world = getMessageFromWorldService();
        HelloworldMessage helloworld = new HelloworldMessage();
        helloworld.setHello(hello);
        helloworld.setWord(world);
        log.debug("Result helloworld message:{}", helloworld);
        return helloworld;
    }

    private HelloMessage getMessageFromHelloService() {
        HelloMessage hello = restTemplate.getForObject("http://hello/message", HelloMessage.class);
        log.debug("From hello service : {}.", hello);
        return hello;
    }

    private WorldMessage getMessageFromWorldService() {
        WorldMessage world = restTemplate.getForObject("http://world/message", WorldMessage.class);
        log.debug("From world service : {}.", world);
        return world;
    }


}

测试:

helloworldfeign调用hello服务和world服务

feign方式调用服务,项目代码参考:helloworldfeign
pom.xml引入feignx

       <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>

配置启动类注解:

package com.example.helloworldfeign;

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

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class HelloworldFeignApplication {

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

被调用接口HelloService

package com.example.helloworldfeign.service;

import com.example.helloworldfeign.model.HelloMessage;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

/**
 * @author billjiang 475572229@qq.com
 * @create 17-8-23
 */
@FeignClient(value="hello")
public interface HelloService {

    @GetMapping("/message")
    HelloMessage hello();


}

被调用接口WorldService

package com.example.helloworldfeign.service;

import com.example.helloworldfeign.model.WorldMessage;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

/**
 * @author billjiang 475572229@qq.com
 * @create 17-8-23
 */
@FeignClient(value="world")
public interface WorldService {

    @GetMapping("/message")
    WorldMessage world();

}

入口类HelloworldController:

package com.example.helloworldfeign.controller;

import com.example.helloworldfeign.model.HelloMessage;
import com.example.helloworldfeign.model.HelloworldMessage;
import com.example.helloworldfeign.model.WorldMessage;
import com.example.helloworldfeign.service.HelloService;
import com.example.helloworldfeign.service.WorldService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author billjiang 475572229@qq.com
 * @create 17-8-23
 */
@RestController
public class HelloworldController {

    private static final Logger log = LoggerFactory.getLogger(HelloworldController.class);

    private static final String HELLO_SERVICE_NAME = "hello";

    private static final String WORLD_SERVICE_NAME = "world";

    @Autowired
    private HelloService helloService;

    @Autowired
    private WorldService worldService;

    @GetMapping("/")
    public String home() {
        return "hello world";
    }

    @GetMapping("/message")
    public HelloworldMessage getMessage() {
        HelloMessage hello = helloService.hello();
        WorldMessage world = worldService.world();
        HelloworldMessage helloworld = new HelloworldMessage();
        helloworld.setHello(hello);
        helloworld.setWord(world);
        log.debug("Result helloworld message:{}", helloworld);
        return helloworld;
    }

}

为了更好的地查看效果,hello服务和world服务可以启动多个实例,并把调用实例的ip和端口输出来。

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