一服務降級的說明

1.1 服務降級說明

"服務器忙，請稍后在試"不讓客戶達等待，立即返回一個友好的提示。

1.2 服務降級的觸發情況

1.程序運行異常；

2.超時；

3.服務熔斷觸發服務降級；4

.線程池/信號量打滿也會導致服務降級

1.3 通用注解

1.4? hystrix的作用

在springcloud的框架里，熔斷機制是通過hystrix實現，hystrix會監控服務之間的調用。當失敗調用達到一定的閾值，默認是5s內失敗20次，就會啟用hystrix的熔斷機制，使用命令@HystrixCommand。

二案例：對每一個方法實行降級處理

2.1 消費端

2.1.1 pom文件

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

2.1.2 設置降級規則

代碼

 @GetMapping(value = "/consumer/payment/nacos/{id}")@HystrixCommand(fallbackMethod = "dealFallBackInfo",commandProperties = {@HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="1500")})public String paymentInfo(@PathVariable("id") Long id){System.out.println("獲取服務器配置信息serverUrl:"+serverURL);System.out.println("9008的controller獲取id:"+id);String str=orderConsumerService.getPaymentByIdLjf22222(id);return "ok:"+serverURL+""+str;}@GetMapping(value = "/consumer/getinfo/{id}")public Object getUserInfo(@PathVariable("id") Long id){User u=new User(id.intValue(),"beijing"+id);return  orderConsumerService.postQueryParams(u);}public String dealFallBackInfo(@PathVariable("id") Long id){return "我是消費者9008,服務出錯了，進行服務降級"+id;}

?2.1.3 開啟hystrix熔斷

添加：@EnableHystrix 注解

?2.2?服務端

2.2.1 pom文件

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

2.2.2?設置降級規則

1.代碼

    @GetMapping(value = "/ljf/getinfo/{id}")@HystrixCommand(fallbackMethod = "dealFallBackInfo",commandProperties = {@HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="3000")})public String getPayment(@PathVariable("id") Integer id){try {Thread.sleep(5000);} catch (InterruptedException e) {e.printStackTrace();}int k=10/0;System.out.println("================服務9009 獲取到的參數id:"+id);return "服務9009 獲取到的參數id:"+id;}@PostMapping("/path")public  String postQueryParams(@RequestBody User user) throws JsonProcessingException {String str=  new JsonMapper().writeValueAsString(user);System.out.println("post提交....");return str;}public String dealFallBackInfo(@PathVariable("id") Long id){return "我是消費者9009,服務出錯了，進行服務降級"+id;}

2.截圖

?2.2.3 開啟hystrix熔斷

??2.3?啟動服務測試

1.啟動nacos，啟動sleuth

2.啟動consumer9008? ?provider9009

?3.測試

三案例：設置全局降級處理辦法

3.1 消費端設置

1.代碼

package com.ljf.mscloud.controller;import com.ljf.mscloud.model.User;
import com.ljf.mscloud.service.OrderConsumerService;
import com.netflix.hystrix.contrib.javanica.annotation.DefaultProperties;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;/*** @ClassName: OrderConsumerController* @Description: TODO* @Author: admin* @Date: 2023/08/14?18:09:14?* @Version: V1.0**/
@RestController
@Slf4j
@RefreshScope //支持Nacos的動態刷新功能。
//@DefaultProperties(defaultFallback = "globalFallBackInfo")
public class OrderConsumerController {@Value("${service-url.nacos-user-service}")private String serverURL;@Autowiredprivate OrderConsumerService orderConsumerService;@GetMapping(value = "/consumer/payment/nacos/{id}")@HystrixCommand(fallbackMethod = "dealFallBackInfo",commandProperties = {@HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="1500")})public String paymentInfo(@PathVariable("id") Long id){System.out.println("獲取服務器配置信息serverUrl:"+serverURL);System.out.println("9008的controller獲取id:"+id);String str=orderConsumerService.getPaymentByIdLjf22222(id);return "ok:"+serverURL+""+str;}@GetMapping(value = "/consumer/getinfo/{id}")public Object getUserInfo(@PathVariable("id") Long id){User u=new User(id.intValue(),"beijing"+id);return  orderConsumerService.postQueryParams(u);}public String dealFallBackInfo(@PathVariable("id") Long id){return "我是消費者9008,服務出錯了，進行服務降級"+id;}public String globalFallBackInfo(){return "Global異常處理信息，請稍后再試，客戶端9008";}
}

2.截圖

?原因在沒有在制定方法加：@HystrixCommand? 那么加上此注解后：

?再次訪問：http://localhost:9008/consumer/getinfo/666

四案例：給Feginclient注解的接口上添加降級規則

4.1 controller

package com.ljf.mscloud.controller;import com.ljf.mscloud.model.User;
import com.ljf.mscloud.service.OrderConsumerService;
import com.netflix.hystrix.contrib.javanica.annotation.DefaultProperties;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;/*** @ClassName: OrderConsumerController* @Description: TODO* @Author: admin* @Date: 2023/08/14?18:09:14?* @Version: V1.0**/
@RestController
@Slf4j
@RefreshScope //支持Nacos的動態刷新功能。
//
//@DefaultProperties(defaultFallback = "globalFallBackInfo")
public class OrderConsumerController {@Value("${service-url.nacos-user-service}")private String serverURL;@Autowiredprivate OrderConsumerService orderConsumerService;@GetMapping(value = "/consumer/payment/nacos/{id}")//   @HystrixCommand(fallbackMethod = "dealFallBackInfo",commandProperties = {//        @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="1500")// })public String paymentInfo(@PathVariable("id") Long id){System.out.println("獲取服務器配置信息serverUrl:"+serverURL);System.out.println("9008的controller獲取id:"+id);String str=orderConsumerService.getPaymentByIdLjf22222(id);return "ok:"+serverURL+""+str;}@GetMapping(value = "/consumer/getinfo/{id}")// @HystrixCommandpublic Object getUserInfo(@PathVariable("id") Long id){User u=new User(id.intValue(),"beijing"+id);//  int age = 10/0;return  orderConsumerService.postQueryParams(u);}public String dealFallBackInfo(@PathVariable("id") Long id){return "我是消費者9008,服務出錯了，進行服務降級"+id;}public String globalFallBackInfo(){return "Global異常處理信息，請稍后再試，客戶端9008";}
}

4.2 service

package com.ljf.mscloud.service;import com.ljf.mscloud.model.User;
import feign.Headers;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
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;@Component
@FeignClient(value = "mscloud-fegin-nacos-hystrix-provider9009",fallback = PaymentFallbackService.class)
public interface OrderConsumerService {@GetMapping(value = "/ljf/getinfo/{yyid}") //相當于：public String getPaymentByIdLjf22222(@PathVariable("yyid") Long ssid);// @Headers({"Content-Type: application/json"})// @PostMapping("/path")@PostMapping(value = "/path",consumes ="application/json")String postQueryParams(@RequestBody User user);
}

4.3 fallback實現類

@Component
public class PaymentFallbackService  implements OrderConsumerService{@Overridepublic String getPaymentByIdLjf22222(Long ssid) {return "getPaymentByIdLjf22222方法出現問題開始降級";}@Overridepublic String postQueryParams(User user) {return "postQueryParams方法出現問題開始降級";}
}