0.9.0.RELEASE版本的spring cloud alibaba sentinel+feign降級處理實例

　　既然用到了feign，那么主要是針對服務消費方的降級處理。我們基於0.9.0.RELEASE版本的spring cloud alibaba nacos+feign實例添油加醋，把sentinel功能加上去：

　　1、pom引入sentinel依賴：

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

　　2、application配置哨兵控制台地址、開啟feign+sentinel：

#哨兵
spring.cloud.sentinel.transport.dashboard=localhost:8080
#打開sentinel
feign.sentinel.enabled=true

　　3、啟動類在@FeignClient注解中指定降級處理類和配置類：

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class TransConsumerApplication {

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

    @Slf4j
    @RestController
    static class TestController {

        @Autowired
        private ApplicationApi applicationApi;

        @GetMapping("/sayhello")
        public String sayhello() {
            return "say: " + applicationApi.hello();
        }

        @GetMapping("/sayhey")
        public String sayhey() {
            return "say: " + applicationApi.hey();
        }

    }

    @FeignClient(name = "lxytrans-provider", fallback = TestFallback.class, configuration = FeignConfiguration.class)
    interface ApplicationApi {

        @GetMapping("/hello")
        String hello();

        @GetMapping("/hey")
        String hey();

    }

    class TestFallback implements ApplicationApi {

        @Override
        public String hello() {
            return "hello feign fallback.";
        }

        @Override
        public String hey() {
            return "hey feign fallback.";
        }
    }

    class FeignConfiguration {
        @Bean
        public TestFallback testFallback() {
            return new TestFallback();
        }
    }

}

　　跑起來后，調用一把這兩個接口，可以發現哨兵控制台多了消費方：

　　此處無需配置流控、降級，我們的服務方維持原來的流控、降級處理（參見0.9.0.RELEASE版本的spring cloud alibaba sentinel限流、降級處理實例）。調用sayhey，服務方時延2秒，超時直接熔斷：

 

　　再讓消費方通過jmeter調用sayhello，前面3個正常返回，后面兩個因為服務方限流而熔斷：