SpringCloud灾难性雪崩效应处理方法之降级实现流程详解

一.前言

解决服务雪崩效应，都是避免application client请求application service时，出现服务调用错误或网络问题。处理手法都是在application client中实现。我们需要在application client相关工程中导入hystrix依赖信息。并在对应的启动类上增加新的注解@EnableCircuitBreaker，这个注解是用于开启hystrix熔断器的，简言之，就是让代码中的hystrix相关注解生效。

二.代码实现

1.新建ApplicationServiceDemo

1.1配置pom.xml

需要web和eureka-client

<parent>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-parent</artifactId>
   <version>2.3.5.RELEASE</version>
</parent>
<dependencyManagement>
   <dependencies>
       <dependency>
           <groupId>org.springframework.cloud</groupId>
           <artifactId>spring-cloud-dependencies</artifactId>
           <version>Hoxton.SR9</version>
           <type>pom</type>
           <scope>import</scope>
       </dependency>
   </dependencies>
</dependencyManagement>
<dependencies>
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
   <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
   </dependency>
</dependencies>

1.2新建配置文件

spring:
  application:
    name: application-service-demo
eureka:
  client:
    service-url:
      defaultZone: http://eurekaserver1:8761/eureka/

1.3新建控制器

@Controller
public class DemoController {
   @RequestMapping("/demo")
   @ResponseBody
   public String demo(){
       return "demo-service";
   }
}

1.4新建启动类

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

2.新建DemoFallback

新建项目DemoFallback作为Application Client

2.1编写pom.xml

需要配置web,eureka-client,netflix-hystrix

<parent>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-parent</artifactId>
   <version>2.3.5.RELEASE</version>
</parent>
<dependencyManagement>
   <dependencies>
       <dependency>
           <groupId>org.springframework.cloud</groupId>
           <artifactId>spring-cloud-dependencies</artifactId>
           <version>Hoxton.SR9</version>
           <type>pom</type>
           <scope>import</scope>
       </dependency>
   </dependencies>
</dependencyManagement>
<dependencies>
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
   <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
   </dependency>
   <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
   </dependency>
</dependencies>

2.2新建配置文件

spring:
  application:
    name: fallback-demo
eureka:
  client:
    service-url:
      defaultZone: http://eurekaserver1:8761/eureka/
server:
  port: 8081

2.3新建配置类

@Configuration
public class RibbonConfig {
   @Bean
   @LoadBalanced
   public RestTemplate restTemplate(){
       return new RestTemplate();
   }
}

2.4新建service及实现类

public interface DemoService {
   String test();
}

@Service
public class DemoServiceImpl implements DemoService {
   @Autowired
   private RestTemplate restTemplate;
   @HystrixCommand(fallbackMethod = "myFallback")
   @Override
   public String test() {
       String result = restTemplate.postForObject("http://application-service-demo/demo", null, String.class);
       System.out.println(result);
       return result;
   }
   public String myFallback(){
       return "托底数据";
   }
}

2.5新建控制器

@Controller
public class FallbackController {
   @Autowired
   private DemoService demoService;
   @RequestMapping("/demo")
   @ResponseBody
   public String demo(){
       return demoService.test();
   }
}

2.6新建启动类

@SpringBootApplication
@EnableCircuitBreaker
public class ApplicationClientApplication {
   public static void main(String[] args) {
       SpringApplication.run(ApplicationclientdemoApplication.class, args);
   }
}

2.7访问

在浏览器输入http://localhost:8081/demo

3.测试降级

停止ApplicationServiceDemo项目。再次访问

来源：https://blog.csdn.net/qq_43966957/article/details/128076830