Ribbon 服务消费者

1.1 RestTemplate

Ribbon对RestTemplate进行了封装，提供负载均衡和重试功能。RestTemplate是Spring Boot提供的一个远程调用工具，可以执行GET和POST等请求。

RestTemplate 的方法

getForObject("url", 转换类型, 提交的参数)

`postForObject("url", 协议体数据, 转换类型)"

修改 sp06-ribbon 项目

新建项目

项目名称：sp06-ribbon

依赖项：
- spring-boot-starter-parent
- spring-boot-starter-web
- spring-cloud-starter-netflix-eureka-client
- sp01-commons

application.yml

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

主程序

添加 @EnableDiscoveryClient 注解

创建 RestTemplate 实例

1.2 RibbonController

@RestControllerpublic class RibbonController {    @Autowired    private RestTemplate rt;    @GetMapping("/item-service/{orderId}")    public JsonResult getItem(@PathVariable String orderId) {        return rt.getForObject("http://item-service/{1}", JsonResult.class, orderId);    }    @PostMapping("/item-service/decreaseNumber")    public JsonResult decreaseNumber(@RequestBody List
   
     items) {        return rt.postForObject("http://item-service/decreaseNumber", items, JsonResult.class);    }    @GetMapping("/user-service/{userId}")    public JsonResult getUser(@PathVariable Integer userId) {        return rt.getForObject("http://user-service/{1}", JsonResult.class, userId);    }    @GetMapping("/user-service/{userId}/score")    public JsonResult addScore(@PathVariable Integer userId, Integer score) {        return rt.getForObject("http://user-service/{1}/score?score={2}", JsonResult.class, userId, score);    }    @GetMapping("/order-service/{orderId}")    public JsonResult 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/", JsonResponse.class);    }}

1.3 启动服务并测试

项目启动
```
mvn spring-boot:run
```

访问测试
- http://eureka1:2001
- http://localhost:3001/item-service/decreaseNumber
- 使用 Postman Sending POST 请求，请求体为 [{"id":1, "name":"abc", "number":23},{"id":2, "name":"def", "number":11}]

2.1 Ribbon 负载均衡

修改项目

添加 ripple 依赖


        
     
      org.springframework.cloud
         
     
      spring-cloud-starter-netflix-ribbon

在主程序中加 @LoadBalanced 注解

访问路径改为服务ID

2.2 Ribbon 重试

添加 retry 依赖


        
     
      org.springframework.retry
         
     
      spring-retry

在 application.yml 配置重试参数

spring:  application:    name: ribbon    server:      port: 3001  eureka:    client:      service-url:        defaultZone: http://eureka1:2001/eureka, http://eura2:2002/eureka      ribbon:        MaxAutoRetries: 1        MaxAutoRetriesNextServer: 2        OkToRetryOnAllOperations: true

设置超时时间

@Beanpublic RestTemplate getRestTemplate() {    SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();    factory.setConnectTimeout(1000);    factory.setReadTimeout(1000);    return new RestTemplate(factory);}

修改 ItemController 添加延迟

@Slf4j@RestControllerpublic class ItemController {    @Autowired    private ItemService itemService;    @Value("${server.port}")    private int port;    @GetMapping("/{orderId}")    public JsonResult getItem(@PathVariable String orderId) throws Exception {        log.info("server.port = {}, orderId = {}", port, orderId);        if (Math.random() < 0.6) {            log.info("temp sleep: {}", new Random().nextInt(5000));            Thread.sleep(new Random().nextInt(5000));        }        List
    
      items = itemService.getItems(orderId);        return JsonResult.ok(items);    }}

测试

负载均衡测试
- 同时访问 http://localhost:3001/item-service/decreaseNumber

重试测试
- ItemService 降低响应速度，测试Ribbon的自动重试能力

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