Spring Cloud Alibaba之限流与防护组件Sentinel

实例演示1：通过Sentinel实现限流

创建SentinelDemo的Maven项目，配置pom文件：

 <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
        </dependency>
</dependencies>

编写启动类：

package prj;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

编写application.properties配置文件：

spring.application.name=SentinelDemo
# 与Sentinel控制台交互的端口
spring.cloud.sentinel.transport.port=9000
# sentinel控制台的工作地址和端口
spring.cloud.sentinel.transport.dashboard=localhost:8090

编写Controller控制类ContrllerForLimit：

@RestController
public class ControllerForLimit {

    @RequestMapping("/sayHello")
    @SentinelResource(value = "sayHello")
    public String sayHello() {
        return "Hello Sentinel";
    }

    @RequestMapping("/useSentinel")
    @SentinelResource(value = "useSentinel")
    public String useSentinel() {
        return "Use Sentinel";
    }

}

控制台设置限流参数，运行项目观察效果

实例演示2：实现热点限流效果

在SentinelDemo项目的基础上，新增控制类ContrllerForHotPot：

@RestController
public class ControllerForHotSpot {
    @RequestMapping("/buyItem")
    @SentinelResource(value = "buyItem")
    public String buyItem(@RequestParam(value = "item", required = false) String item,
                             @RequestParam(value = "price", required = false) String price) {
        return "Hot Spot Demo";
    }
}

控制台设置热点限流参数，观察效果

实例演示3：实现熔断限流效果

在SentinelDemo项目的基础上，新增控制类ContrllerForFusing：

@RestController
public class ControllerForFusing {
    @RequestMapping("/testFusing")
    @SentinelResource(value = "testFusing")
    public String testFusing() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "Test Fusing";
    }
}

控制台设置慢调用比例参数后，编写测试类，运行项目观察熔断效果：

class RequestThread extends Thread{
    public void run() {
        RestTemplate restTemplate = new RestTemplate();
        ResponseEntity<String> entity = restTemplate.getForEntity("http://localhost:8080/testFusing", String.class);
        System.out.println(entity.getBody());
    }
}
public class TestFusing {
    public static void main(String[] args){
        for(int i = 0;i<1000;i++) {
            new RequestThread().start();
        }
    }
}

实例演示4：实现服务降级效果

在控制类ContrllerForLimit，添加limitForHandle的服务方法

@RestController
public class ControllerForLimit {

    @RequestMapping("/sayHello")
    @SentinelResource(value = "sayHello")
    public String sayHello() {
        return "Hello Sentinel";
    }

    @RequestMapping("/useSentinel")
    @SentinelResource(value = "useSentinel")
    public String useSentinel() {
        return "Use Sentinel";
    }

    @RequestMapping("/limitForHandler")
    @SentinelResource(value = "limitForHandler",fallback ="handleException")
    public String limitForHandler() {
        return "limitForHandler";
    }

    public String handleException() {
        return "handler limit Exception";
    }
}