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SpringCloud学习笔记 - @SentinelResource的fallbackblockHandler配置详解 - sentinel

news 2025/9/15 21:32:44

1. sentinel服务负载均衡测试

sentinel默认开启了负载均衡的轮询模式，为了测试sentinel服务负载均衡的效果，需要先创建两个服务提供者和一个服务消费者。

1.1. 分别创建两个服务提供者-支付服务9003、9004

1. 添加pom依赖： 提供者只需要将自己注册到服务注册中心即可，因此只需要添加spring-cloud-starter-alibaba-nacos-discovery。

	<dependencies><!--自定义api--><dependency><groupId>com.atguigu.springboot</groupId><artifactId>cloud-api-commons</artifactId><version>1.0-SNAPSHOT</version></dependency><!--nacos服务发现--><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><!--springboot web--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency><!--日常通用jar包--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-devtools</artifactId><scope>runtime</scope><optional>true</optional></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies>

2. 编写yaml配置文件： 注意给两个服务分配不同的端口9003、9004

server:port: 9003spring:application:name: nacos-payment-providercloud:nacos:discovery:server-addr: localhost:8848management:endpoints:web:exposure:include: "*"

3. 创建主启动类

@SpringBootApplication
@EnableDiscoveryClient
public class PaymentMain9003 {public static void main(String[] args) {SpringApplication.run(PaymentMain9003.class,args);}
}

4. 创建业务类

package com.atguigu.alibaba.controller;import com.atguigu.springcloud.entities.CommonResult;
import com.atguigu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;import java.util.HashMap;/*** @author 强浩* @version 1.0.0* Copyright(c) YTANG All Rights Reserved* @className* @project 管理系统* @date 2022年09月14日*/
@RestController
@Slf4j
public class PaymentController {@Value("${server.port}")private String serverPort;//模拟数据库public static HashMap<Long, Payment> hashMap = new HashMap<>();static {hashMap.put(1L, new Payment(1L,"28a8c1e3bc2742d8848569891fb42181"));hashMap.put(2L,new Payment(2L,"bba8c1e3bc2742d8848569891ac32182"));hashMap.put(3L,new Payment(3L,"6ua8c1e3bc2742d8848569891xt92183"));}//传入id获取数据@GetMapping(value = "/paymentSQL/{id}")public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id){Payment payment = hashMap.get(id);CommonResult<Payment> commonResult = new CommonResult(200, "from mysql,serverPort:  " + serverPort, payment);return commonResult;}
}

2. 创建服务消费者-订单服务84

1. 添加pom依赖： 因为之后需要使用sentinel进行限流，所以需要添加sentinel的依赖

    <dependencies><dependency><groupId>com.atguigu.springboot</groupId><artifactId>cloud-api-commons</artifactId><version>1.0-SNAPSHOT</version></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-sentinel</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-devtools</artifactId><scope>runtime</scope><optional>true</optional></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies>

2. 配置application.yaml文件：

server:port: 84spring:application:name: nacos-order-consumercloud:nacos:discovery:server-addr: localhost:8848sentinel:transport:dashboard: localhost:8080port: 8719server_url:payment_provider: http://nacos-payment-provider

3. 创建主启动类：

@SpringBootApplication
@EnableDiscoveryClient
public class OrderMain84 {public static void main(String[] args) {SpringApplication.run(OrderMain84.class,args);}
}

4. 创建RestTemplate服务调用配置类：

package com.atgugui.alibaba.config;import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;/*** @author 强浩* @version 1.0.0* Copyright(c) YTANG All Rights Reserved* @className* @project 管理系统* @date 2022年09月14日*/
@Configuration
public class ApplicationContextConfig {@Bean@LoadBalancedpublic RestTemplate getRestTemplate(){return new RestTemplate();}
}

5. 创建业务类： 注入RestTemplate进行远程服务调用

package com.atgugui.alibaba.controller;import com.atguigu.springcloud.entities.CommonResult;
import com.atguigu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;import javax.annotation.Resource;/*** @author 强浩* @version 1.0.0* Copyright(c) YTANG All Rights Reserved* @className* @project 管理系统* @date 2022年09月14日*/
@RestController
@Slf4j
public class CircleBreakerController {public static final String SERVER_URL = "http://nacos-payment-provider";@Resourceprivate RestTemplate restTemplate;@GetMapping("/consumer/fallback/{id}")public CommonResult<Payment> fallback(@PathVariable("id") Long id){CommonResult<Payment> result = restTemplate.getForObject(SERVER_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;}
}

5. 测试访问： 查看负载均衡的轮询效果
访问 http://localhost:84/consumer/fallback/1，多次访问，通过观察端口号可以发现，对支付服务进行了轮询访问。

2. fallback-业务错误处理

fallback只负责业务异常

1. 添加@SentinelResource注解，并配置fallback参数，指定服务降级处理方法

    @GetMapping("/consumer/fallback/{id}")@SentinelResource(value = "fallback", fallback = "handlerFallback")//指定fallback服务降级处理方法public CommonResult<Payment> fallback(@PathVariable("id") Long id){CommonResult<Payment> result = restTemplate.getForObject(SERVER_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;}public CommonResult<Payment> 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);}

2. 测试： http://localhost:84/consumer/fallback/5，在没有降级处理的时候会直接报错，添加了fallback后进入降级处理方法。
在这里插入图片描述

3. blockHandler-限流规则处理

blockHandler处理违反了限流规则的请求

1. 给fallback方法资源添加限流规则
在这里插入图片描述

2. 配置@SentinelResource的blockHandler参数指定流控服务降级方法

    @GetMapping("/consumer/fallback/{id}")@SentinelResource(value = "fallback", blockHandler = "blockHandler")public CommonResult<Payment> fallback(@PathVariable("id") Long id){CommonResult<Payment> result = restTemplate.getForObject(SERVER_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;}public CommonResult<Payment> 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);}

3. 测试：http://localhost:84/consumer/fallback/5
在这里插入图片描述

4. 服务熔断fallback和blockHandler同时配置

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。也就是说会优先处理服务限流，保证高可用，不要卡死服务器。

@RestController
@Slf4j
public class CircleBreakerController {public static final String SERVER_URL = "http://nacos-payment-provider";@Resourceprivate RestTemplate restTemplate;@GetMapping("/consumer/fallback/{id}")@SentinelResource(value = "fallback", blockHandler = "blockHandler", fallback = "handlerFallback")public CommonResult<Payment> fallback(@PathVariable("id") Long id){CommonResult<Payment> result = restTemplate.getForObject(SERVER_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;}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);}public CommonResult<Payment> 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);}
}

5. exceptionsToIgnore忽略指定异常

@RestController
@Slf4j
public class CircleBreakerController {public static final String SERVER_URL = "http://nacos-payment-provider";@Resourceprivate RestTemplate restTemplate;@GetMapping("/consumer/fallback/{id}")@SentinelResource(value = "fallback", blockHandler = "blockHandler", fallback = "handlerFallback",exceptionsToIgnore = IllegalArgumentException.class)public CommonResult<Payment> fallback(@PathVariable("id") Long id){CommonResult<Payment> result = restTemplate.getForObject(SERVER_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;}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);}public CommonResult<Payment> 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);}}

设置了忽略IllegalArgumentException异常，当出现该异常时不会进入降级逻辑。
在这里插入图片描述

6. sentinel整合openFeign实现服务熔断降级

一般在消费端添加feign组件实现服务降级：在84消费端添加openFeign的依赖，实现服务的熔断降级。

1. 引入openFeign的pom依赖： 这里因为版本冲突问题，需要将devtools组件取消掉，目前具体冲突原因还不知道。

<dependencies><dependency><groupId>com.atguigu.springboot</groupId><artifactId>cloud-api-commons</artifactId><version>1.0-SNAPSHOT</version></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><!--添加openFeign依赖--><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-alibaba-sentinel</artifactId><version>0.2.2.RELEASE</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency><!--<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-devtools</artifactId><scope>runtime</scope><optional>true</optional></dependency>--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies>

2. 修改yaml文件，添加fegin对sentinel的支持：

server:port: 84spring:application:name: nacos-order-consumercloud:nacos:discovery:server-addr: localhost:8848sentinel:transport:dashboard: localhost:8080port: 8719server_url:payment_provider: http://nacos-payment-providerfeign:sentinel:enabled: true

3. 在主启动类开启openFeign：

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class OrderMain84 {public static void main(String[] args) {SpringApplication.run(OrderMain84.class,args);}
}

4. 编写业务类： 使用@FeignClient注解，指定要进行访问的微服务名称，和发生熔断时所要调用的fallback方法

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

5. 服务降级方法实现类： 相当于给PaymentService增加了一个实现类，在发生熔断的情况下自动调用方法的fallback实现，来快速返回结果，防止系统卡死。

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

6. 现在就可以使用openFeign进行远程服务调用，我们只需要像之前一样将服务接口注入到controller层中，即可实现无感的远程服务调用了:

@RestController
@Slf4j
public class CircleBreakerController {//注入openFeign远程调用接口@Resourceprivate PaymentService paymentService;@GetMapping(value = "/consumer/paymentSQL/{id}")public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id){CommonResult<Payment> result = paymentService.paymentSQL(id);return result;}
}

7. 测试： 访问 http://localhost:84/consumer/paymentSQL/2，此时将9003服务提供者断开，84消费侧自动降级，不会被耗死。
在这里插入图片描述

7. 各熔断框架比较

SentinelHystrixresilience4j
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
拓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
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