spingcloud(6)hystrix服务降级

众多的服务串在一起，虽然避免了耦合性，但却形成了闭合链，只要其中一环失效，就会造成整个服务死锁，这个时候hystrix就可以发挥作用了，将服务降级，

采用替代的方案来顶替出现错误的方法，避免整个链路中断。

fallback是对于整个应用来说的，服务提供者和消费者端都可以进行配置，但一般都会配置在客户端，对于用户进行反馈。

1.服务提供者。

yml文件都是常规配置

server:
  port: 8001
spring:
  application:
    name: cloud-provider-hystrix-payment
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      #defaultZone: http://localhost:7001/eureka
      defaultZone: http://eureka7001.com:7001/eureka/

启动类加上断路器注解

@EnableCircuitBreaker

service测试类

@Service
public class PaymentHystrixService {
    public String paymentinfo_ok(Integer id){
        return "线程池:"+Thread.currentThread().getName()+"paymentinfo_ok,id:"+id+"	"+"成功！！！！";
    }
    @HystrixCommand(fallbackMethod = "paymentinfo_Timeouthander",commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
    })
   public String paymentinfo_timeout(Integer id){
        int timenum=5;
       try {
           TimeUnit.SECONDS.sleep(timenum);
       } catch (InterruptedException e) {
           e.printStackTrace();
       }
       return "线程池:"+Thread.currentThread().getName()+"paymentinfo_timeout,id:"+id+"	"+"失败！！！！耗时(秒):"+timenum;
   }
   public String paymentinfo_Timeouthander(@PathVariable("id") Integer id){
       return "线程池:"+Thread.currentThread().getName()+"系统繁忙，请稍后重试,id:"+id+"	"+"失败！！！！o(╥﹏╥)o";
   }
}

controller采用feign配合调用接口，服务提供者端也可以采用hystrix进行服务降级。

@RestController
@Slf4j
public class PaymentHystrixController {
    @Resource
    private PaymentHystrixService paymentHystrixService;

    @GetMapping(value = "/payment/hystrix/ok/{id}")
    public String payment_ok(@PathVariable("id")Integer id){
        String result = paymentHystrixService.paymentinfo_ok(id);
        log.info("*****result:"+result);
         return result;
    }
    @GetMapping(value = "/payment/hystrix/timeout/{id}")
    public String payment_timeout(@PathVariable("id")Integer id){
        String result = paymentHystrixService.paymentinfo_timeout(id);
        log.info("*****result:"+result);
        return result;
    }
}

2.客户端消费者

yml文件常规配置需要加上新的feign，hystrix配置

server:
  port: 80
#这里只把feign做客户端用，不注册进eureka
eureka:
  client:
    #表示是否将自己注册进EurekaServer默认为true
    register-with-eureka: false
    fetch-registry: true
    service-url:
      #defaultZone: http://localhost:7001/eureka
      defaultZone: http://eureka7001.com:7001/eureka/
feign:
  hystrix:
    enabled: true

采用openfeign调用接口，创建service接口，fallback后续介绍

@Component
@FeignClient(value = "CLOUD-PROVIDER-HYSTRIX-PAYMENT",fallback = PaymentFallback.class)
public interface PaymentHystrixService {
    @GetMapping(value = "/payment/hystrix/ok/{id}")

    public String payment_ok(@PathVariable("id")Integer id);

    @GetMapping(value = "/payment/hystrix/timeout/{id}")
    public String payment_timeout(@PathVariable("id")Integer id);
}

启动类常规配置，加上hystrix注解

@SpringBootApplication
@EnableFeignClients
@EnableHystrix

controller

@RestController
@Slf4j
public class OrderController {
    @Resource
    private PaymentHystrixService paymentHystrixService;

    @GetMapping(value = "/consumer/payment/hystrix/ok/{id}")
    public String payment_ok(@PathVariable("id")Integer id){
        String result = paymentHystrixService.payment_ok(id);
        return result;
    }
    @GetMapping(value = "/consumer/payment/hystrix/timeout/{id}")
    /*@HystrixCommand(fallbackMethod = "paymentinfo_Timeouthander",commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "1500")
    })*/
    public String payment_timeout(@PathVariable("id")Integer id){
        String result = paymentHystrixService.payment_timeout(id);
        return result;
    }
 
}

在面对服务降级的处理中，随着服务的增多，越来越多的方法需要配置一个独立的fallback,而且在同一个类中会造成代码膨胀和耦合度增强，此时需要采取额外的方法，创建额外的fallback类继承openfeign的调用接口

，此时fallback的作用就是当服务正常的时候不触发，若是出现方法报错或者服务端宕机就会自动去调取fallback类中对应的方法。

@Component
public class PaymentFallback implements PaymentHystrixService
{
    @Override
    public String payment_ok(Integer id) {
        return "服务失败了，o(╥﹏╥)o";
    }
    @Override
    public String payment_timeout(Integer id) {
        return "服务超时或者运行报错，o(╥﹏╥)o";
    }
}

 本篇所有代码均在GitHub：

https://github.com/MaTsukun/springcloud2020