SpringClub03-ribbon负载均衡和重试

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一、ribbon 服务消费者

ribbon 提供了负载均衡和重试功能, 它底层是使用 RestTemplate 进行 Rest api 调用

1.RestTemplate

RestTemplate 是SpringBoot提供的一个Rest远程调用工具

它的常用方法:

  • getForObject() – 执行get请求
  • postForObject() – 执行post请求

之前的系统结构是浏览器直接访问后台服务

后面我们通过一个Demo项目演示 Spring Cloud 远程调用

下面我们先不使用ribbon, 单独使用RestTemplate来执行远程调用

1.1 新建 sp06-ribbon 项目

1.2 修改pom文件

  • eureka-client 中已经包含 ribbon 依赖
  • 需要添加 sp01-commons 依赖
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>cn.tedu</groupId>
<artifactId>sp06-ribbon</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>sp06-ribbon</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Hoxton.RELEASE</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>cn.tedu</groupId>
<artifactId>sp01-commons</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

1.3 修改application.yml

spring:
application:
name: ribbon
server:
port: 3001
eureka:
client:
service-url:
defaultZone: http://eureka1:2001/eureka, http://eureka2:2002/eureka

1.4 主程序

  • 创建 RestTemplate 实例

    RestTemplate 是用来调用其他微服务的工具类，封装了远程调用代码，提供了一组用于远程调用的模板方法，例如： getForObject() 、 postForObject() 等 

package cn.tedu.sp06;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@EnableDiscoveryClient
@SpringBootApplication
public class Sp06RibbonApplication {
//创建 RestTemplate 实例，并存入 spring 容器
@Bean
public RestTemplate getRestTemplate() {
return new RestTemplate();
}
public static void main(String[] args) {
SpringApplication.run(Sp06RibbonApplication.class, args);
}
}

1.5 创建 RibbonController 类

package com.tedu.sp06.controller;
import cn.tedu.sp01.pojo.Item;
import cn.tedu.sp01.pojo.Order;
import cn.tedu.sp01.pojo.User;
import cn.tedu.web.util.JsonResult;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;
import java.util.List;
@RestController
@Slf4j
public class RibbonController {
@Autowired
private RestTemplate rt;
@GetMapping("/item-service/{orderId}")
public JsonResult<List<Item>> getItems(@PathVariable String orderId) {
// 调用远程的商品服务，获得订单的商品列表
// {1} - RestTemplate自己定义的一种站位符格式
return rt.getForObject("http://localhost:8001/{1}",
JsonResult.class,
orderId); //用 orderId 填充占位符 {1} }
@PostMapping("/item-service/decreaseNumber")
public JsonResult<?> decreaseNumber(@RequestBody List<Item> items) {
return rt.postForObject(
"http://localhost:8001/decreaseNumber",
items,
JsonResult.class);
}
@GetMapping("/user-service/{userId}")
public JsonResult<User> getUser(@PathVariable Integer userId) {
return rt.getForObject("http://localhost:8101/{1}",
JsonResult.class,
userId);
}
@GetMapping("/user-service/{userId}/score") //    ?score=1000
public JsonResult<?> addScore(@PathVariable Integer userId,
@RequestParam Integer score) {
return rt.getForObject("http://localhost:8101/{1}/score?score={2}",
JsonResult.class,
userId, score);
}
@GetMapping("/order-service/{orderId}")
public JsonResult<Order> getOrder(@PathVariable String orderId) {
return rt.getForObject("http://localhost:8201/{1}",
JsonResult.class,
orderId);
}
@GetMapping("/order-service/")
public JsonResult<?> addOrder() {
return rt.getForObject("http://localhost:8201/",JsonResult.class);
}
}

1.6 启动服务，并访问测试

http://eureka1:2001

http://localhost:3001/item-service/35

http://localhost:3001/item-service/decreaseNumber

使用postman，POST发送以下格式数据：

[{"id":1, "name":"abc", "number":23},{"id":2, "name":"def", "number":11}]

http://localhost:3001/user-service/7

http://localhost:3001/user-service/7/score?score=100

http://localhost:3001/order-service/123abc

http://localhost:3001/order-service/

2. ribbon 负载均衡和重试

2.1 Ribbon 负载均衡

2.1.1 添加 ribbon 依赖

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

2.1.2 RestTemplate 设置 @LoadBalanced

@LoadBalanced 负载均衡注解，会对 RestTemplate 实例进行封装，创建动态代理对象，并切入（AOP）负载均衡代码，把请求分发到集群中的服务器 

package cn.tedu.sp06;
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;
@EnableDiscoveryClient
@SpringBootApplication
public class Sp06RibbonApplication {
@LoadBalanced //负载均衡注解
@Bean
public RestTemplate getRestTemplate() {
return new RestTemplate();
}
public static void main(String[] args) {
SpringApplication.run(Sp06RibbonApplication.class, args);
}
}

2.1.3 访问路径设置为服务id

package cn.tedu.sp06.controller;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
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.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import cn.tedu.sp01.pojo.Item;
import cn.tedu.sp01.pojo.Order;
import cn.tedu.sp01.pojo.User;
import cn.tedu.web.util.JsonResult;
@RestController
public class RibbonController {
@Autowired
private RestTemplate rt;
@GetMapping("/item-service/{orderId}")
@HystrixCommand(fallbackMethod = "getItemsFB")
public JsonResult<List<Item>> getItems(@PathVariable String orderId) {
//调用远程的商品服务，获得订单的商品列表
//{1} - RestTemplate自己定义的一种站位符格式
@PostMapping("/item-service/decreaseNumber")
public JsonResult<?> decreaseNumber(@RequestBody List<Item> items) {
return rt.postForObject("http://item-service/decreaseNumber", items, JsonResult.class);
}
@GetMapping("/user-service/{userId}")
public JsonResult<User> getUser(@PathVariable Integer userId) {
return rt.getForObject("http://user-service/{1}", JsonResult.class, userId);
}
@GetMapping("/user-service/{userId}/score") // ?score=1000
public JsonResult<?> addScore(@PathVariable Integer userId, @RequestParam Integer score) {
return rt.getForObject("http://user-service/{1}/score?score={2}", JsonResult.class, userId, score);
}
@GetMapping("/order-service/{orderId}")
public JsonResult<Order> getOrder(@PathVariable String orderId) {
return rt.getForObject("http://order-service/{1}", JsonResult.class, orderId);
}
@GetMapping("/order-service")
public JsonResult<?> addOrder() {
return rt.getForObject("http://order-service", JsonResult.class);
}

2.1.4 访问测试

2.2 ribbon 重试

2.2.1 添加 ribbon 依赖

<dependency>
<groupId>org.springframework.retry</groupId>
<artifactId>spring-retry</artifactId>
</dependency>

2.2.2 配置 application.yml

spring:
application:
name: ribbon
server:
port: 3001
#连接eureka
eureka:
client:
service-url:
defaultZone: http://eureka1:2001/eureka, http://eureka2:2002/eureka
ribbon:
#单台重试次数
MaxAutoRetries: 1
#更换服务器次数
MaxAutoRetriesNextServer: 2

2.2.3 主程序设置 RestTemplate 的请求工厂的超时属性

package com.tedu.sp06;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
@EnableCircuitBreaker//启用断路器
public class Sp06RibbonApplication {
public static void main(String[] args) {
SpringApplication.run(Sp06RibbonApplication.class, args);
}
//创建 RestTemplate 实例，并存入 spring 容器
@LoadBalanced//负载均衡注解,对 RestTemplate 进行封装,增强RestTemplate的功能
@Bean
public RestTemplate getRestTemplate (){
SimpleClientHttpRequestFactory f=new SimpleClientHttpRequestFactory();
//两个超时参数默认-1，表示不启用
f.setConnectTimeout(1000);
f.setReadTimeout(1000);
return new RestTemplate();
}
}

2.2.4 ItemController 添加延迟代码，以便测试 ribbon 的重试机制

package cn.tedu.sp02.item.controller;
import cn.tedu.sp01.pojo.Item;
import cn.tedu.sp01.service.ItemService;
import cn.tedu.web.util.JsonResult;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.*;
import java.util.List;
import java.util.Random;
@RestController
@Slf4j
public class ItemController {
@Autowired
private ItemService itemService;
// 为了后面测试集群多台服务器，这里注入端口号
@Value("${server.port}")
private int port;
@GetMapping("/{orderId}")
public JsonResult<List<Item>> getItems(@PathVariable String orderId) throws InterruptedException {
log.info("orderId="+orderId+", port="+port);
//添加随机延迟代码
if (Math.random()<0.9){
//随机产生0到5000的随机延迟时长
long t=new Random().nextInt(5000);
log.info("延迟:"+t);
Thread.sleep(t);
}
//
List<Item> items = itemService.getItems(orderId);
return JsonResult.ok().msg("port="+port).data(items);
}
// 只处理post请求
// @RequestBody 注解，完整接收post请求协议体数据
@PostMapping("/decreaseNumber")
public JsonResult<?> decreaseNumber(@RequestBody List<Item> items) {
itemService.decreaseNumber(items);
return JsonResult.ok().msg("减少商品库存成功");
}
}

2.2.5 测试 ribbon 重试机制

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