SpringCloud（5）-使用斷路器

由於網絡原因或者自身的原因，服務並不能保證100%可用，如果單個服務出現問題，調用這個服務就會出現線程阻塞，此時若有大量的請求涌入，Servlet容器的線程資源會被消耗完畢，導致服務癱瘓。服務與服務之間的依賴性，故障會傳播，會對整個微服務系統造成災難性的嚴重後果，這就是服務故障的“雪崩”效應。

爲了解決這個問題，業界提出了斷路器模型

斷路器的使用

1. pom.xml的配置依賴

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

2. application.properties的配置

   server.port=85
   spring.application.name=consume
   eureka.client.service-url.defaultZone=http://master:81/eureka/
   feign.hystrix.enabled=true
   

3. 啓動類

   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
   import org.springframework.cloud.netflix.hystrix.EnableHystrix;
   import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
   import org.springframework.cloud.openfeign.EnableFeignClients;
   
   @SpringBootApplication
   @EnableFeignClients
   @EnableDiscoveryClient
   @EnableHystrix
   @EnableHystrixDashboard
   public class EurekaHelloConsumeApplication {
   
       public static void main(String[] args) {
           SpringApplication.run(EurekaHelloConsumeApplication.class, args);
       }
   }
   

4. Feign請求的接口類

   import org.springframework.cloud.openfeign.FeignClient;
   import org.springframework.web.bind.annotation.RequestMapping;
   import org.springframework.web.bind.annotation.RequestMethod;
   import org.springframework.web.bind.annotation.RequestParam;
   
   @FeignClient(value = "provider",fallback = FeignServiceImpl.class)
   public interface FegionService {
   
       @RequestMapping(method = RequestMethod.GET)
        String feignHello(@RequestParam(value = "name") String name);
   }
   

5. 在fegin中使用，寫一個feginServiceImpl繼承接口FegionService

   import org.springframework.stereotype.Component;
   
   @Component
   public class FeignServiceImpl implements FegionService {
       @Override
       public String feignHello(String name) {
           return "暫時無法訪問";
       }
   }
   

6. 在Ribbon中使用斷路器

   import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.stereotype.Service;
   import org.springframework.web.client.RestTemplate;
   
   @Service
   public class ConsumeService {
       @Autowired
       private RestTemplate restTemplate;
       @HystrixCommand(fallbackMethod = "consumeHelloError")
       public String consumeHello(){
           return restTemplate.getForObject("http://provider?name=唐陳",String.class);
       }
       public String consumeHelloError(){
           return "暫時無法訪問";
       }
   }