一、介绍

（1）提供界面配置配置服务限流、服务降级、服务熔断
（2）@SentinelResource的blockHandler只处理后台配置的异常，运行时异常fallBack处理，且资源名为value时才生效，走兜底方法

二、安装并启动sentinel

（1）官网
（2）运行java -jar sentinel-dashboard-1.8.6.jar
（3）访问http://localhost:8080/

注：sentinel是懒加载的，访问接口后才会显示

三、搭建项目

（1）编写pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>demo20220821</artifactId><groupId>com.wsh.springcloud</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>cloudalibaba-sentinel-service</artifactId><dependencies><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-sentinel</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-sentinel-datasource</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-nacos-config</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>com.wsh.springcloud</groupId><artifactId>cloud-api-common</artifactId><version>1.0-SNAPSHOT</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.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies></project>

（2）编写application.yml

server:port: 8401spring:application:name: cloudalibaba-sentinel-servicecloud:nacos:discovery:server-addr: localhost:8848sentinel:transport:dashboard: localhost:8080port: 8719management:endpoints:web:exposure:include: "*"

（3）编写启动类

package com.wsh.springcloud;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;/*** @ClassName SentinelService8401* @Description: TODO* @Author wshaha* @Date 2023/10/19* @Version V1.0**/
@SpringBootApplication
@EnableDiscoveryClient
public class SentinelService8401 {public static void main(String[] args) {SpringApplication.run(SentinelService8401.class, args);}
}

（4）编写Controller

package com.wsh.springcloud.controller;import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;/*** @ClassName TestController* @Description: TODO* @Author wshaha* @Date 2023/10/19* @Version V1.0**/
@RestController
public class TestController {@GetMapping("/test")public String test(){return "test";}
}

四、服务限流

（1）打开界面

（2）阈值
QPS：每秒请求数
并发线程数：处理请求的线程数

（3）关联

/test炸了，/test1也炸

（4）预热，阈值先从阈值/3开始，在预热时长（单位：秒）内逐渐上升

（5）排队等待，阈值类型必须设置为QPS，超出阈值的请求将会排队，等待的超时时间设置为20秒

五、服务降级

（1）满足条件后，服务在规定时间内熔断
（2）慢调用比例

（3）异常比例

（4）异常数

六、热点参数限流

（1）要用@SentinelResource定义资源名和兜底方法

    @GetMapping("/test2")@SentinelResource(value = "test2", blockHandler = "test2_solve")public String test2(@RequestParam("name") String name) {log.info("test2");return "test2";}public String test2_solve(String name, BlockException blockException){return "block";}

（2）

（3）定义规则时指定参数的值

七、兜底方法编写方式优化

（1）

    @GetMapping("/test3")@SentinelResource(value = "test3",  blockHandlerClass = BlockHandler.class, blockHandler = "test3_solve")public String test3() {log.info("test3");return "test3";}

（2）编写BlockHandler类

package com.wsh.springcloud.handler;import com.alibaba.csp.sentinel.slots.block.BlockException;/*** @ClassName BlockHandler* @Description: TODO* @Author wshaha* @Date 2023/10/19* @Version V1.0**/
public class BlockHandler {public static String test3_solve(BlockException blockException){return "block";}
}

（3）

八、配置fallback、blockHandler

（1）exceptionsToIgnore 用于忽略异常，不走fallback

    @GetMapping("/test3")@SentinelResource(value = "test3", blockHandlerClass = BlockHandler.class, blockHandler = "test3_solve",fallbackClass = FallBackHandler.class, fallback = "test3_solve1",exceptionsToIgnore = NullPointerException.class)public String test3(@RequestParam("name") String name) {if (name.equals("wsh")){throw new IllegalArgumentException();}return "test3";}

（2）

public class BlockHandler {public static String test3_solve(String name, BlockException blockException){return "block";}
}

public class FallBackHandler {public static String test3_solve1(String name, Throwable throwable){return "block1";}
}

九、配置openFeign

（1）编写pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>demo20220821</artifactId><groupId>com.wsh.springcloud</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>cloudalibaba-consumer-order84</artifactId><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-sentinel</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-sentinel-datasource</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>com.wsh.springcloud</groupId><artifactId>cloud-api-common</artifactId><version>1.0-SNAPSHOT</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.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies></project>

（2）编写application.yml

server:port: 84spring:application:name: cloudalibaba-consumer-ordercloud:nacos:discovery:server-addr: localhost:8848sentinel:transport:dashboard: localhost:8080port: 8719management:endpoints:web:exposure:include: "*"server-url: http://cloudalibaba-provider-paymentfeign:sentinel:enabled: true

（3）编写启动类

package com.wsh.springcloud;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;/*** @ClassName ConsumerOrder84* @Description: TODO* @Author wshaha* @Date 2023/10/19* @Version V1.0**/
@EnableDiscoveryClient
@EnableFeignClients
@SpringBootApplication
public class ConsumerOrder84 {public static void main(String[] args) {SpringApplication.run(ConsumerOrder84.class, args);}
}

（4）编写PaymentService

package com.wsh.springcloud.service;import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;/*** @ClassName PaymentService* @Description: TODO* @Author wshaha* @Date 2023/10/19* @Version V1.0**/
@FeignClient(value = "cloudalibaba-provider-payment", fallback = PaymentServiceHandler.class)
public interface PaymentService {@GetMapping("/payment/test")public String test();
}

（5）编写fallback类

package com.wsh.springcloud.service;import org.springframework.stereotype.Component;/*** @ClassName PaymentServiceHandler* @Description: TODO* @Author wshaha* @Date 2023/10/19* @Version V1.0**/
@Component
public class PaymentServiceHandler implements PaymentService{@Overridepublic String test() {return "fallback";}
}

（6）编写Controller

package com.wsh.springcloud.controller;import com.wsh.springcloud.service.PaymentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;/*** @ClassName TestController* @Description: TODO* @Author wshaha* @Date 2023/10/19* @Version V1.0**/
@RestController
public class TestController {@Autowiredprivate PaymentService paymentService;@GetMapping("/consumer/test")public String test(){return paymentService.test();}
}

（7）编写服务提供者Controller

package com.wsh.springcloud.controller;import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;/*** @ClassName TestController* @Description: TODO* @Author wshaha* @Date 2023/10/18* @Version V1.0**/
@RestController
public class TestController {@Value("${server.port}")private String port;@GetMapping("/payment/test")public String test(){int i = 1 / 0;return "test: " + port;}
}

（8）运行

十、配置持久化

（1）将规则持久化到nacos保存，只能先在nacos里编写好才有效
（2）pom.xml增加依赖

        <dependency><groupId>com.alibaba.csp</groupId><artifactId>sentinel-datasource-nacos</artifactId></dependency>

（3）修改application.yml

    sentinel:transport:dashboard: localhost:8080port: 8719datasource:dsl:nacos:server-addr: localhost:8848dataId: cloudalibaba-sentinel-servicegroupId: DEFAULT_GROUPdata-type: jsonrule-type: flow

（4）nacos里创建配置

[{"resource": "/consumer/test","limitApp": "default","grade": "1","count": 1,"strategy": 0,"controlBehavior": 0,"clusterMode": false}
]