服务熔断

Sentinel服务熔断无配置

没有任何配置 - 给用户error页面，不友好

@RestController
@Slf4j
public class CircleBreakerController {
    public static final String SERVICE_URL = "http://nacos-payment-provider";

    @Resource
    private RestTemplate restTemplate;
 
    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback")//没有配置
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }
        return result;
    }
}

服务熔断只配置fallback

fallback只负责业务异常

@RestController
@Slf4j
public class CircleBreakerController {
    public static final String SERVICE_URL = "http://nacos-payment-provider";
    @Resource
    private RestTemplate restTemplate;
    @RequestMapping("/consumer/fallback/{id}")
    //@SentinelResource(value = "fallback")//没有配置
    @SentinelResource(value = "fallback", fallback = "handlerFallback") //fallback只负责业务异常
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }
        return result;
    }
    
    //本例是fallback
    public CommonResult handlerFallback(@PathVariable  Long id,Throwable e) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(444,"兜底异常handlerFallback,exception内容  "+e.getMessage(),payment);
    }
}

测试地址 - http://localhost:84/consumer/fallback/4

只配置blockHandler

blockHandler只负责Sentinel控制台配置违规

@RestController
@Slf4j
public class CircleBreakerController {
    public static final String SERVICE_URL = "http://nacos-payment-provider";
    @Resource
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
    //@SentinelResource(value = "fallback") //没有配置
    //@SentinelResource(value = "fallback",fallback = "handlerFallback") //fallback只负责业务异常
    @SentinelResource(value = "fallback",blockHandler = "blockHandler") //blockHandler只负责sentinel控制台配置违规
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }
        return result;
    }
    //本例是fallback
/*    public CommonResult handlerFallback(@PathVariable  Long id,Throwable e) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(444,"兜底异常handlerFallback,exception内容  "+e.getMessage(),payment);
    }*/
    
    //本例是blockHandler
    public CommonResult blockHandler(@PathVariable  Long id,BlockException blockException) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException  "+blockException.getMessage(),payment);
    }
}

测试地址 - http://localhost:84/consumer/fallback/4

fallback和blockHandler都配置

若blockHandler和fallback 都进行了配置，则被限流降级而抛出BlockException时只会进入blockHandler处理逻辑。

@RestController
@Slf4j
public class CircleBreakerController {
    public static final String SERVICE_URL = "http://nacos-payment-provider";
    @Resource
    private RestTemplate restTemplate;
    @RequestMapping("/consumer/fallback/{id}")
    //@SentinelResource(value = "fallback") //没有配置
    //@SentinelResource(value = "fallback",fallback = "handlerFallback") //fallback只负责业务异常
    //@SentinelResource(value = "fallback",blockHandler = "blockHandler") //blockHandler只负责sentinel控制台配置违规
    @SentinelResource(value = "fallback",fallback = "handlerFallback",blockHandler = "blockHandler")
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }
        return result;
    }
    //本例是fallback
    public CommonResult handlerFallback(@PathVariable  Long id,Throwable e) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(444,"兜底异常handlerFallback,exception内容  "+e.getMessage(),payment);
    }
    //本例是blockHandler
    public CommonResult blockHandler(@PathVariable  Long id,BlockException blockException) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException  "+blockException.getMessage(),payment);
    }
}

exceptionsToIgnore

exceptionsToIgnore，忽略指定异常，即这些异常不用兜底方法处理。

@RestController
@Slf4j
public class CircleBreakerController  {
    ...
    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback",fallback = "handlerFallback",blockHandler = "blockHandler",
            exceptionsToIgnore = {IllegalArgumentException.class})//<-------------
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
        if (id == 4) {
            //exceptionsToIgnore属性有IllegalArgumentException.class，
            //所以IllegalArgumentException不会跳入指定的兜底程序。
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }
        return result;
    }
	...
}

服务熔断OpenFeign

84消费者调用提供者9003，Feign组件一般是消费侧。

<!--SpringCloud openfeign -->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

yml

# 激活Sentinel对Feign的支持
feign:
  sentinel:
    enabled: true

业务类

带@Feignclient注解的业务接口，fallback = PaymentFallbackService.class

@FeignClient(value = "nacos-payment-provider",fallback = PaymentFallbackService.class)
public interface PaymentService {
    @GetMapping(value = "/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id);
}

@Component
public class PaymentFallbackService implements PaymentService {
    @Override
    public CommonResult<Payment> paymentSQL(Long id) {
        return new CommonResult<>(44444,"服务降级返回,---PaymentFallbackService",new Payment(id,"errorSerial"));
    }
}

Controller

@RestController
@Slf4j
public class CircleBreakerController {
    ...
	//==================OpenFeign
    @Resource
    private PaymentService paymentService;

    @GetMapping(value = "/consumer/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id)  {
        return paymentService.paymentSQL(id);
    }
}

主启动类

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@EnableDiscoveryClient
@SpringBootApplication
@EnableFeignClients//<------------------------
public class OrderNacosMain84 {
    public static void main(String[] args) {
        SpringApplication.run(OrderNacosMain84.class, args);
    }
}

测试，http://localhost:84/consumer/paymentSQL/1，测试84调用9003，此时故意关闭9003微服务提供者，84消费侧自动降级，不会被耗死。

熔断框架比较

比较项	Sentinel	Hystrix	resilience4j
隔离策略	信号量隔离（并发线程数限流）	线程池隔商/信号量隔离	信号量隔离
熔断降级策略	基于响应时间、异常比率、异常数	基于异常比率	基于异常比率、响应时间
实时统计实现	滑动窗口（LeapArray）	滑动窗口（基于RxJava）	Ring Bit Buffer
动态规则配置	支持多种数据源	支持多种数据源	有限支持
扩展性	多个扩展点	插件的形式	接口的形式
基于注解的支持	支持	支持	支持
限流	基于QPS，支持基于调用关系的限流	有限的支持	Rate Limiter
流量整形	支持预热模式匀速器模式、预热排队模式	不支持	简单的Rate Limiter模式
系统自适应保护	支持	不支持	不支持
控制台	提供开箱即用的控制台，可配置规则、查看秒级监控，机器发观等	简单的监控查看	不提供控制台，可对接其它监控系统

规则持久化

Sentinel规则持久化：一旦我们重启应用，sentinel规则将消失，生产环境需要将配置规则进行持久化。

将限流配置规则持久化进Nacos保存，只要刷新8401某个rest地址，sentinel控制台的流控规则就能看到，只要Nacos里面的配置不删除，针对8401上sentinel上的流控规则持续有效。

步骤

修改cloudalibaba-sentinel-service8401

POM

<!--SpringCloud ailibaba sentinel-datasource-nacos 后续做持久化用到-->
<dependency>
    <groupId>com.alibaba.csp</groupId>
    <artifactId>sentinel-datasource-nacos</artifactId>
</dependency>

YML

server:
  port: 8401

spring:
  application:
    name: cloudalibaba-sentinel-service
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848 #Nacos服务注册中心地址
    sentinel:
      transport:
        dashboard: localhost:8080 #配置Sentinel dashboard地址
        port: 8719
      datasource: #<----------------关注点，添加Nacos数据源配置
        ds1:
          nacos:
            server-addr: localhost:8848
            dataId: cloudalibaba-sentinel-service
            groupId: DEFAULT_GROUP
            data-type: json
            rule-type: flow

management:
  endpoints:
    web:
      exposure:
        include: '*'

feign:
  sentinel:
    enabled: true # 激活Sentinel对Feign的支持

添加Nacos业务规则配置

配置内容解析

[{
    "resource": "/rateLimit/byUrl",
    "IimitApp": "default",
    "grade": 1,
    "count": 1, 
    "strategy": 0,
    "controlBehavior": 0,
    "clusterMode": false
}]

resource：资源名称；
limitApp：来源应用；
grade：阈值类型，0表示线程数, 1表示QPS；
count：单机阈值；
strategy：流控模式，0表示直接，1表示关联，2表示链路；
controlBehavior：流控效果，0表示快速失败，1表示Warm Up，2表示排队等待；
clusterMode：是否集群。

启动8401后刷新sentinel发现业务规则有了

快速访问测试接口 - http://localhost:8401/rateLimit/byUrl - 页面返回Blocked by Sentinel (flow limiting)，停止8401再看sentinel - 停机后发现流控规则没有了。

重新启动8401再看sentinel，乍一看还是没有，稍等一会儿，多次调用 - http://localhost:8401/rateLimit/byUrl，重新配置出现了，持久化验证通过。

目录CONTENT

Sentinel熔断和持久化