Spring-Cloud-Ribbon学习笔记（一）：入门

简介

Spring Cloud Ribbon是一个基于Http和TCP的客户端负载均衡工具，它是基于Netflix Ribbon实现的。它不像服务注册中心、配置中心、API网关那样独立部署，但是它几乎存在于每个微服务的基础设施中。理解Ribbon对于我们使用Spring Cloud来讲非常的重要，因为负载均衡是对系统的高可用、网络压力的缓解和处理能力扩容的重要手段之一。

在Spring Cloud中，有两种服务调用方式，一种是Ribbon+RestTemplate，另一种是Feign。文本先讲解下基于Ribbon+RestTemplate的用法。

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。

实现

新建服务spring-cloud-ribbon

pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.yan</groupId>

    <artifactId>spring-cloud-ribbon</artifactId>

    <version>1.0-SNAPSHOT</version>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.1.0.RELEASE</version>

        <relativePath/>

    </parent>

    <dependencyManagement>

        <dependencies>

            <dependency>

                <groupId>org.springframework.cloud</groupId>

                <artifactId>spring-cloud-dependencies</artifactId>

                <version>Finchley.RELEASE</version>

                <type>pom</type>

                <scope>import</scope>

            </dependency>

        </dependencies>

    </dependencyManagement>

    <dependencies>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-ribbon</artifactId>

            <version>RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-config</artifactId>

            <version>RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-eureka</artifactId>

            <version>RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

            <version>RELEASE</version>

        </dependency>

    </dependencies>

</project>

配置

yml

server:

  port: 8004

spring:

  application:

    name: spring-cloud-ribbon

  cloud:

    config:

      discovery:

        enabled: true

        service-id: spring-cloud-config-server

  profiles:

    active: dev

eureka:

  client:

    serviceUrl:

      defaultZone: http://localhost:8761/eureka/

启动类

核心是配有注解@LoadBalanced的RestTemplate的Bean配置

package com.yan;

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.context.annotation.Configuration;

import org.springframework.web.client.RestTemplate;

@SpringBootApplication

@Configuration

@EnableDiscoveryClient

public class RibbonApplication {

    public static void main(String[] args) {

        SpringApplication.run(RibbonApplication.class, args);

    }

    @Bean

    @LoadBalanced

    public RestTemplate restTemplate() {

        return new RestTemplate();

    }

}

Controller

package com.yan.controller;

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.http.HttpEntity;

import org.springframework.web.bind.annotation.*;

import org.springframework.web.client.RestTemplate;

import java.util.StringJoiner;

@RestController

@RequestMapping("/ribbon")

public class RibbonController {

    private final RestTemplate template;

    @Autowired

    public RibbonController(RestTemplate template) {

        this.template = template;

    }

    @GetMapping("/get")

    public Object get(String svcName, String url, String className) {

        Class<?> clazz = getResponseType(className);

        String uri = getUrl(svcName, url);

        return template.getForObject(uri, clazz);

    }

    @PostMapping("/post")

    public Object post(@RequestParam String svcName, @RequestParam String url, @RequestParam String className, @RequestBody HttpEntity<?> httpEntity) throws JsonProcessingException {

        Class<?> clazz = getResponseType(className);

        String url1 = getUrl(svcName, url);

        Object res = template.postForObject(url1, httpEntity, clazz);

        String resJson = new ObjectMapper().writeValueAsString(res);

        System.out.println(resJson);

        return res;

    }

    private Class<?> getResponseType(@RequestParam String className) {

        Class<?> clazz;

        try {

            clazz = Class.forName(className);

        } catch (ClassNotFoundException e) {

            clazz = String.class;

        }

        return clazz;

    }

    private String getUrl(String svcName, String url) {

        StringJoiner stringJoiner = new StringJoiner("/");

        String uri = stringJoiner.add(svcName).add(url).toString().replaceAll("/+", "/");

        return "http://" + uri;

    }

}

测试

假如我有两个名叫svcA的服务，同时注册到同一个Eureka上，只是端口号不同，它们都有一个post接口定义如下：

    @Value("${server.port}")

    private int port;

    @PostMapping("/post/{name}")

    public String post(@PathVariable String name, @RequestBody String type) {

        return "svcA:" + port + "===>\n" + "name:" + name + "\ntype:" + type;

    }

打开Postman：

发送请求：http://localhost:8004/ribbon/post?svcName=SVCA&url=/post/xixi&className=java.lang.String

Header：{'Content-Type': 'application/json'}

Body: {'raw': {

{

"headers": {"Content-Type": ["application/json"]},

"body": "haha"

}

}}

多次点击发送请求，在ribbon服务下看到日志:

"svcA:8081===>\nname:xixi\ntype:haha"

"svcA:8087===>\nname:xixi\ntype:haha"

"svcA:8081===>\nname:xixi\ntype:haha"

"svcA:8087===>\nname:xixi\ntype:haha"

"svcA:8081===>\nname:xixi\ntype:haha"

"svcA:8087===>\nname:xixi\ntype:haha"

两个服务交替接收请求，这说明Ribbon配置生效了。

巴特西

Spring-Cloud-Ribbon学习笔记（一）：入门

简介

实现

新建服务spring-cloud-ribbon

配置

启动类

Controller

测试

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