Spring Cloud（七）不使用starter的情况下使用Alibaba Sentinel

我们在使用Alibaba Sentinel时一般都是在pom文件中引入spring-cloud-starter-alibaba-sentinel，这个工程会带来非常多的jar包，这里面有些是和可视化监控有关的，有些是和webflux有关的，等等。如果我们并不需要可视化监控，不涉及到webflux，那么这个starter虽然给我们带来方便，但同时也使得无用的依赖jar包数量增加不少。如何让jar包尽可能少？本文尝试通过只添加两个和sentinel有关的包来实现一个流控规则。

1、配置pom.xml文件

<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">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.github.ralgond</groupId>
	<artifactId>sentinel-demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>


	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.0.RELEASE</version>
	</parent>

	<dependencies>
		<dependency>
			<groupId>com.alibaba.csp</groupId>
			<artifactId>sentinel-core</artifactId>
			<version>1.8.0</version>
		</dependency>
		<dependency>
			<groupId>com.alibaba.csp</groupId>
			<artifactId>sentinel-annotation-aspectj</artifactId>
			<version>1.8.0</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.0</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>

	</build>
</project>

2、编写主类

package com.github.ralgond.sentineldemo.e1;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.RuleConstant;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRuleManager;


@SpringBootApplication
@RestController
public class FlowController {
	
	public AtomicLong pass = new AtomicLong(0);
	public AtomicLong block = new AtomicLong(0);
	
	@SentinelResource(value="get", blockHandler="blockHandler")
	@RequestMapping(method=RequestMethod.GET, value="/get")
	public String get() {
		pass.incrementAndGet();
		return "success";
	}
	
	public String blockHandler(BlockException ex) {
		block.incrementAndGet();
		return "failed";
	}
	
	@RequestMapping(method=RequestMethod.GET, value="/metric")
	public String metric() {
		return ""+pass.get()+"|"+block.get();
	}
	
	
	public static void main(String args[]) {
		initFlowRules();
		SpringApplication.run(FlowController.class, args);
	}
	
    private static void initFlowRules() {
        List<FlowRule> rules = new ArrayList<>();
        FlowRule rule = new FlowRule();
        rule.setResource("get");
        rule.setGrade(RuleConstant.FLOW_GRADE_QPS);
        rule.setCount(1);
        rules.add(rule);
        
        FlowRuleManager.loadRules(rules);
    }
}

3、配置和@SentinelResource有关的AOP类

@Configuration
public class SentinelE1Configuration {

	@Bean
	public SentinelResourceAspect sentinelResourceAspect() {
		return new SentinelResourceAspect();
	}
}

4、运行

启动主类，在浏览器输入http://localhost:8080/get，快速点击，你会发现时而出现success，大部分时间出现failed，再在浏览器输入http://localhost:8080/metric可以看到通过数和block数。