 <!--SpringCloud openfeign -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

激活Sentinel對Feign的支持

spring:
application:
name: nacos-order-consumer
cloud:
nacos:
discovery:
#Nacos服務(wù)注冊中心地址
server-addr: localhost:8848
sentinel:
transport:
#配置Sentinel dashboard地址
dashboard: localhost:8080
#默認8719端口，假如被占用會自動從8719開始依次+1掃描,直至找到未被占用的端口
port: 8719
management:
endpoints:
web:
exposure:
include: '*'
# 激活Sentinel對Feign的支持
feign:
sentinel:
enabled: true

# 激活Sentinel對Feign的支持

feign:

sentinel:

enabled: true

增加業(yè)務(wù)類接口

@FeignClient(value = "nacos-payment-provider",fallback = PaymentFallbackService.class)//調(diào)用中關(guān)閉9003服務(wù)提供者
public interface PaymentService
{
    @GetMapping(value = "/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id);
}

@FeignClient(value = "nacos-payment-provider",fallback =PaymentFallbackService.class)//調(diào)用中關(guān)閉9003服務(wù)提供者

@Component
public class PaymentFallbackService implements PaymentService
{
    @Override
    public CommonResult<Payment> paymentSQL(Long id)
    {
        return new CommonResult<>(444,"服務(wù)降級返回,沒有該流水信息",new Payment(id, "errorSerial......"));
    }
}

調(diào)用失敗的時候，就會調(diào)用重寫的方法

修改控制類

 //==================OpenFeign
    @Resource
    private PaymentService paymentService;
    @GetMapping(value = "/consumer/openfeign/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id)
    {
        if(id == 4)
        {
            throw new RuntimeException("沒有該id");
        }
        return paymentService.paymentSQL(id);
    }

添加@EnableFeignClients啟動Feign的功能

@EnableDiscoveryClient
@SpringBootApplication
@EnableFeignClients
public class OrderNacosMain84
{
    public static void main(String[] args) {
            SpringApplication.run(OrderNacosMain84.class, args);
    }
}

測試

啟動9003 9004 84 端口

訪問：http://localhost:84/consumer/paymentSQL/1

測試84調(diào)用9003，此時故意關(guān)閉9003微服務(wù)提供者，看84消費側(cè)自動降級，不會被耗死

熔斷框架比較

業(yè)務(wù)降級，是指犧牲非核心的業(yè)務(wù)功能，保證核心功能的穩(wěn)定運行。簡單來說，要實現(xiàn)優(yōu)雅的業(yè)務(wù)降級，需要將功能實現(xiàn)拆分到相對獨立的不同代碼單元，分優(yōu)先級進行隔離。在后臺通過開關(guān)控制，降級部分非主流程的業(yè)務(wù)功能，減輕系統(tǒng)依賴和性能損耗，從而提升集群的整體吞吐率。

降級的重點是：業(yè)務(wù)之間有優(yōu)先級之分。降級的典型應(yīng)用是：電商活動期間關(guān)閉非核心服務(wù)，保證核心買買買業(yè)務(wù)的正常運行。