一 服务降级的说明
1.1 服务降级说明
"服务器忙，请稍后在试"不让客户达等待，立即返回一个友好的提示。
1.2 服务降级的触发情况
1.程序运行异常；
2.超时；
3.服务熔断触发服务降级；4
.线程池/信号量打满也会导致服务降级
1.3 通用注解
二 案例：对每一个方法实行降级处理
2.1 消费端
2.1.1 pom文件
<!--hystrix--><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-hystrix</artifactId></dependency>2.1.2 设置降级规则
代码
@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("获取服务器配置信息serverUrl:"+serverURL);System.out.println("9008的controller获取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 "我是消费者9008,服务出错了，进行服务降级"+id;}
2.1.3 开启hystrix熔断
添加：@EnableHystrix 注解
2.2 服务端
2.2.1 pom文件
<!--hystrix--><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-hystrix</artifactId></dependency>2.2.2 设置降级规则
1.代码
@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("================服务9009 获取到的参数id:"+id);return "服务9009 获取到的参数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 "我是消费者9009,服务出错了，进行服务降级"+id;}2.截图
2.2.3 开启hystrix熔断
2.3 启动服务测试
1.启动nacos，启动sleuth
2.启动consumer9008 provider9009
3.测试
三 案例：设置全局降级处理办法
3.1 消费端设置
1.代码
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的动态刷新功能。
//@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("获取服务器配置信息serverUrl:"+serverURL);System.out.println("9008的controller获取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 "我是消费者9008,服务出错了，进行服务降级"+id;}public String globalFallBackInfo(){return "Global异常处理信息，请稍后再试，客户端9008";}
}
2.截图
原因在没有在制定方法加：@HystrixCommand 那么加上此注解后：
再次访问：http://localhost:9008/consumer/getinfo/666
四 案例：给Feginclient注解的接口上添加降级规则
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的动态刷新功能。
//
//@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("获取服务器配置信息serverUrl:"+serverURL);System.out.println("9008的controller获取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 "我是消费者9008,服务出错了，进行服务降级"+id;}public String globalFallBackInfo(){return "Global异常处理信息，请稍后再试，客户端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}") //相当于：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实现类
@Component
public class PaymentFallbackService implements OrderConsumerService{@Overridepublic String getPaymentByIdLjf22222(Long ssid) {return "getPaymentByIdLjf22222方法出现问题开始降级";}@Overridepublic String postQueryParams(User user) {return "postQueryParams方法出现问题开始降级";}
}4.4 配置文件
4.5 测试
1.故意只启动 consuemr9008，不启动provider9009 模拟宕机的情况
2.测试
