SpringCloud—-解决灾难性雪崩效应的方法之降级

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