Hystrix的服务降级处理基本使用

曾经终败给现在 2022-12-23 00:36 147阅读 0赞

# 导包 #

SpringCloud和SpringBoot基本依赖这里就不导入了,相信你也导入了

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

# 引导类上开启Hystrix #

在引导类上加上 `@EnableHystrix`或者 `@EnableCircuitBreaker`再在或者 `@SpringCloudApplication`

import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.SpringCloudApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.netflix.hystrix.EnableHystrix;
    import org.springframework.context.annotation.Bean;
    import org.springframework.http.converter.StringHttpMessageConverter;
    import org.springframework.web.client.RestTemplate;
    
    import java.nio.charset.StandardCharsets;
    
    @SpringBootApplication
    //@SpringCloudApplication
    @EnableDiscoveryClient
    @EnableHystrix //开启Hystrix
    public class UserConsumerApplication { 
        public static void main(String[] args) { 
            SpringApplication.run(UserConsumerApplication.class,args);
        }
    
        @Bean
        public RestTemplate restTemplate(){ 
            RestTemplate restTemplate = new RestTemplate();
            restTemplate.getMessageConverters().add(1,new StringHttpMessageConverter(StandardCharsets.UTF_8));
            return restTemplate;
        }
    }

# 在Controller层中添加方法降级方法 #

案例:

public String findByIdFallback(Long id){ 
       return "服务器忙，请稍后重试....";
     }

# 在需要降级的方法添加注解进行降级 #

下方法上添加 `@HystrixCommand(fallbackMethod="方法名称")`  
案例:

@GetMapping("/{id}")
    @HystrixCommand(fallbackMethod="findByIdFallback")  //只针对此方法的降级
    public  String findById(@PathVariable("id") Long id){ 
        String user = restTemplate.getForObject("http://user-service/user/"+id, String.class);
        return user;
    }

# 全局降级 #

每一个方法都需要降级的话,上面的那种就麻烦了,所有`Hystrix`有全局降级

写一个统一的降级方法

public String allMethodFallBack(){ 
       return " 服务器疯狂吃饭中......";
     }

在类上写添加一个注解 `@DefaultProperties(defaultFallback="全局降级方法")`  
在需要使用降级的方法上添加 `@HystrixCommand` ,不加注解的不走降级方法  
**案例**:

import com.leyou.pojo.User;
    import com.netflix.hystrix.contrib.javanica.annotation.DefaultProperties;
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.client.discovery.DiscoveryClient;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.client.RestTemplate;
    import java.util.List;
    
    @RestController
    @RequestMapping("/con")
    @DefaultProperties(defaultFallback = "allMethodFallBack")
    public class UserConsumerController { 
    
        @Autowired
        private RestTemplate restTemplate;
    
        @Autowired
        private DiscoveryClient discoveryClient;
    
        @GetMapping("/{id}")
        @HystrixCommand//降级处理
        public String findById(@PathVariable("id") Long id){ 
            List<ServiceInstance> instances = discoveryClient.getInstances("user-service");
            ServiceInstance serviceInstance = instances.get(0);
            //User user = restTemplate.getForObject("http://localhost:8081/user/"+id, User.class);
            String user = restTemplate.getForObject(serviceInstance.getUri()+"/user/"+id, String .class);
            return user;
        }
    
        public String allMethodFallBack(){ 
            return "服务器干饭中.....";
        }
    }

**Hystix的默认超时时长为1秒，我们可以通过配置修改这个值,直接复制如下即可,这个配置没有提示的**

hystrix:
      command:
        default:
          execution:
            isolation:
              thread:
                timeoutInMilliseconds: 2500 #单位毫秒