4、服务降级

1）先从服务提供方8001找问题

设置自己调用超时时间的峰值，峰值内可以正常运行，超过了需要有兜底的方法，作为降级fullback

2）设置服务提供方8001的fullback

① 一旦调用服务方法失败抛出错误信息或者调用服务超过3秒后，会自动调用@HistrixCommand

中标注好的 fullbackMethod方法

@Service
public class PaymentService {


    public String paymentInfo_ok(Integer id){
        return "线程池："+Thread.currentThread().getName()+
                " paymentInfo_ok,id:"+id+" O(∩_∩)O哈哈~";
    }


    @HystrixCommand(fallbackMethod = "paymentInfo_timeout_handler",
    commandProperties = {
            @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="3000") //程序运行超过3s, 就会进行服务降级
    })
    public String paymentInfo_timeout(Integer id){
        int timenumber=5;
        try {
            TimeUnit.SECONDS.sleep(timenumber);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "线程池："+Thread.currentThread().getName()+
                " paymentInfo_timeout,id:"+id+" 耗时"+timenumber+"秒！！";
    }


    public String paymentInfo_timeout_handler(Integer id){
        return "超时+兜底+ o(╥﹏╥)o";
    }
}

②、主启动类中添加注解 @EnableCircuitBreaker

@SpringBootApplication
@EnableDiscoveryClient
@EnableCircuitBreaker
public class PaymentHystrixMain8001 {
    public static void main(String[] args) {
        SpringApplication.run(PaymentHystrixMain8001.class,args);
    }
}

③ 访问 http://localhost:8001/payment/hystrix/timeout/1，出现下图所示，发现服务确实降级处理了

3）设置服务调用方80fullback处理

服务调用方也可以做自己的服务降级处理

① yml 添加配置

feign:
  hystrix:
    enabled: true

② 主启动类上添加 @EnableHystrix

@SpringBootApplication
@EnableFeignClients
@EnableHystrix
public class ConsumerFeignHystrixMian80 {
    public static void main(String[] args) {
        SpringApplication.run(ConsumerFeignHystrixMian80.class,args);
    }
}

③ 业务类上添加fullback

@RestController
@Slf4j
public class OrderController {

    @Autowired
    private PaymentHystrixService paymentHystrixService;

    @GetMapping("/consumer/payment/hystrix/ok/{id}")
    public String paymentInfo_ok(@PathVariable("id") Integer id)
    {
        String result = paymentHystrixService.paymentInfo_ok(id);
        return result;
    }


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

    public String paymentTimeOutFallbackMethod(@PathVariable("id") Integer id)
    {
        return "我是消费者80,对方支付系统繁忙请10秒钟后再试或者自己运行出错请检查自己,o(╥﹏╥)o";
    }
}

④ 运行结果，访问服务消费侧，调用超过1.5秒就会进行服务降级

http://localhost/consumer/payment/hystrix/timeout/1

4）目前存在的问题？

①、如果每个方法都存在一个兜底的方法时，会造成代码的膨胀

②、业务逻辑的方法和处理异常的fullback方法掺杂在一块

5）解决问题

① 解决代码膨胀的问题

使用注解 @DefaultProperties(defaultFallback = "")，设置默认的全局兜底方法

@RestController
@Slf4j
@DefaultProperties(defaultFallback = "payment_Global_FallbackMethod")
public class OrderController {

    @Autowired
    private PaymentHystrixService paymentHystrixService;

    @GetMapping("/consumer/payment/hystrix/ok/{id}")
    public String paymentInfo_ok(@PathVariable("id") Integer id)
    {
        String result = paymentHystrixService.paymentInfo_ok(id);
        return result;
    }


    @GetMapping("/consumer/payment/hystrix/timeout/{id}")
    @HystrixCommand
    public String paymentInfo_timeout(@PathVariable("id") Integer id)
    {
        String result = paymentHystrixService.paymentInfo_timeout(id);
        return result;
    }

    public String paymentTimeOutFallbackMethod(@PathVariable("id") Integer id)
    {
        return "我是消费者80,对方支付系统繁忙请10秒钟后再试或者自己运行出错请检查自己,o(╥﹏╥)o";
    }

    // 下面是全局fallback方法
    public String payment_Global_FallbackMethod()
    {
        return "Global异常处理信息，请稍后再试，/(ㄒoㄒ)/~~";
    }
}

访问 http://localhost/consumer/payment/hystrix/timeout/1

出现如下情况，全局fullback方法生效

② 解决业务逻辑和fullback逻辑混在一起

只需要为Feign客户端定义的接口添加一个服务降级的处理类即可实现解耦

feign接口

@Component
@FeignClient(value = "CLOUD-PROVIDER-HYSTRIX-PAYMENT",fallback = PaymentHystrixServiceFullbackImpl.class)
public interface PaymentHystrixService {

    @GetMapping("/payment/hystrix/ok/{id}")
    public String paymentInfo_ok(@PathVariable("id") Integer id);

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

服务降级的处理类：

@Service
public class PaymentHystrixServiceFullbackImpl implements PaymentHystrixService{
    @Override
    public String paymentInfo_ok(Integer id) {
        return "==========PaymentHystrixServiceFullbackImpl:paymentInfo_ok==========,o(╥﹏╥)o";
    }

    @Override
    public String paymentInfo_timeout(Integer id) {
        return "==========PaymentHystrixServiceFullbackImpl:paymentInfo_timeout==========,o(╥﹏╥)o";
    }
}

启动eureka和order80 ,但是不启动payment，访问 http://localhost//consumer/payment/hystrix/ok/1 (注意ok方法上并没有加 @histrix),说明 feign的fullback起作用了