阿里开源限流神器Sentinel以及个人对限流总结

朴灿烈づ我的快乐病毒、 2022-03-08 04:42 186阅读 0赞

官网：[https://github.com/alibaba/Sentinel/wiki/%E4%BB%8B%E7%BB%8D][https_github.com_alibaba_Sentinel_wiki_E4_BB_8B_E7_BB_8D]

总结：1.Semaphone信号量限流  2.在spring cloud +RateLimite

你可以发现没有一个框架是直接限流的，Sentinel哨兵框架很棒

它包括限流，熔断，统计等等功能

原理我看不下那个源码，个人能力有限，打扰了，网址：[https://github.com/alibaba/Sentinel/wiki/Sentinel%E5%B7%A5%E4%BD%9C%E4%B8%BB%E6%B5%81%E7%A8%8B][https_github.com_alibaba_Sentinel_wiki_Sentinel_E5_B7_A5_E4_BD_9C_E4_B8_BB_E6_B5_81_E7_A8_8B]

大概意思是：所有的资源对应一个资源名称以及Entry，然后会附带很多插槽，包括限流，熔断...我的理解是通过这个资源名称，来适配这些资源，对他们进行限流等等操作

### 限流： ###

[https://github.com/alibaba/Sentinel/wiki/%E6%B5%81%E9%87%8F%E6%8E%A7%E5%88%B6][https_github.com_alibaba_Sentinel_wiki_E6_B5_81_E9_87_8F_E6_8E_A7_E5_88_B6]

pom.xml

<dependency>
                <groupId>com.alibaba.csp</groupId>
                <artifactId>sentinel-annotation-aspectj</artifactId>
                <version>1.4.1</version>
            </dependency>

demo

public static void main(String[] args) {
            instanceFlowRules();
            Entry entry = null;
            try {
                entry = SphU.entry("HelloWorld");
                System.out.println("HelloWorld");
            } catch (BlockException e) {
                System.out.println("block...");
            } finally {
                if(entry!=null){
                    entry.exit();
                }
            }
        }
    
        private static void instanceFlowRules() {
            List<FlowRule> list = new ArrayList<>();
            FlowRule flowRule = new FlowRule();
            flowRule.setResource("HelloWorld");
    //20qps
            flowRule.setCount(20);
            flowRule.setGrade(RuleConstant.FLOW_GRADE_QPS);
            list.add(flowRule);
            FlowRuleManager.loadRules(list);
        }

### 以QPS方式限流，限流是使用FlowRule ###

如何测试效果？

@ResponseBody
        @RequestMapping(value = "test1")
        public void b() {
            Entry entry = null;
            try {
                entry = SphU.entry("HelloWorld");
                System.out.println("HelloWorld");
            } catch (BlockException e) {
                System.out.println("block...");
            } finally {
                if(entry!=null){
                    entry.exit();
                }
            }
        }

使用apache ab工具，ab -c 100 -n 1000 http://localhost:8080/test1

可以看到会出现blocking...

因为超出阈值的时候，统一抛出BlockExection

### 熔断降级 ###

[https://github.com/alibaba/Sentinel/wiki/%E7%86%94%E6%96%AD%E9%99%8D%E7%BA%A7][https_github.com_alibaba_Sentinel_wiki_E7_86_94_E6_96_AD_E9_99_8D_E7_BA_A7]

官方demo[https://github.com/alibaba/Sentinel/blob/master/sentinel-demo/sentinel-demo-basic/src/main/java/com/alibaba/csp/sentinel/demo/degrade/RtDegradeDemo.java][https_github.com_alibaba_Sentinel_blob_master_sentinel-demo_sentinel-demo-basic_src_main_java_com_alibaba_csp_sentinel_demo_degrade_RtDegradeDemo.java]

对应的是DegradeRule

private static void initDegradeRule() {
            List<DegradeRule> rules = new ArrayList<DegradeRule>();
            DegradeRule rule = new DegradeRule();
            rule.setResource(KEY);
            // set threshold rt, 10 ms
            rule.setCount(10);
            rule.setGrade(RuleConstant.DEGRADE_GRADE_RT);
            rule.setTimeWindow(10);
            rules.add(rule);
            DegradeRuleManager.loadRules(rules);
        }

### 使用注解@SentinelResource ###

[https://github.com/alibaba/Sentinel/wiki/%E6%B3%A8%E8%A7%A3%E6%94%AF%E6%8C%81][https_github.com_alibaba_Sentinel_wiki_E6_B3_A8_E8_A7_A3_E6_94_AF_E6_8C_81]

参数：

*  `value`: 资源名称，必需项（不能为空）
 *  `entryType`: 入口类型，可选项（默认为 `EntryType.OUT`）
 *  `blockHandler `/ `blockHandlerClass`: `blockHandler `对应处理 `BlockException` 的函数名称，可选项。若未配置，则将 `BlockException` **直接抛出**。blockHandler 函数访问范围需要是 `public`，返回类型需要与原方法相匹配，参数类型需要和原方法相匹配并且最后加一个额外的参数，类型为 `BlockException`。blockHandler 函数默认需要和原方法在同一个类中。若希望使用其他类的函数，则可以指定 `blockHandlerClass` 为对应的类的 `Class` 对象，注意对应的函数必需为 static 函数，否则无法解析。
 *  `fallback`: fallback 函数名称，可选项，仅针对降级功能生效（`DegradeException`）。fallback 函数的访问范围需要是 `public`，参数类型和返回类型都需要与原方法相匹配，并且需要和原方法在同一个类中。**业务异常不会进入 fallback 逻辑。**

个人demo

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

实例化注解

import com.alibaba.csp.sentinel.annotation.SentinelResource;
    import com.alibaba.csp.sentinel.slots.block.BlockException;
    import org.springframework.stereotype.Service;
    
    @Service
    public class AServer {
    
        @SentinelResource(value = "test", blockHandler = "exceptionHandler")
        public void HelloWorld() {
            System.out.println("调用get()");
        }
    
        public void exceptionHandler(BlockException e) {
            e.printStackTrace();
            System.out.println("出错！！！");
        }
    }

value资源名称,blockHandler发生BlockExection时进行服务降级

import com.alibaba.csp.sentinel.Entry;
    import com.alibaba.csp.sentinel.SphU;
    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;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    import java.util.ArrayList;
    import java.util.List;
    
    @Controller
    public class AController {
    
        @Autowired
        AServer aServer;
    
        @ResponseBody
        @RequestMapping(value = "test")
        public void a() {
            System.out.println("Hello");
            aServer.HelloWorld();
        }
    
        @ResponseBody
        @RequestMapping(value = "test1")
        public void b() {
            Entry entry = null;
            try {
                entry = SphU.entry("HelloWorld");
                System.out.println("HelloWorld");
            } catch (BlockException e) {
                System.out.println("block...");
            } finally {
                if(entry!=null){
                    entry.exit();
                }
            }
        }
    
    
    
        public static void main(String[] args) {
            //instanceFlowRules();
            Entry entry = null;
            try {
                entry = SphU.entry("HelloWorld");
                System.out.println("HelloWorld");
            } catch (BlockException e) {
                System.out.println("block...");
            } finally {
                if(entry!=null){
                    entry.exit();
                }
            }
        }
    
        private static void instanceFlowRules() {
            List<FlowRule> list = new ArrayList<>();
            FlowRule flowRule = new FlowRule();
            flowRule.setResource("HelloWorld");
            flowRule.setCount(20);
            flowRule.setGrade(RuleConstant.FLOW_GRADE_QPS);
            list.add(flowRule);
            FlowRuleManager.loadRules(list);
        }
    
    }

@SpringBootApplication
    public class DemoApplication {
    
        public static void main(String[] args) {
            instanceFlowRules();
            SpringApplication.run(DemoApplication.class, args);
        }
    
        private static void instanceFlowRules() {
            List<FlowRule> list = new ArrayList<>();
            FlowRule flowRule = new FlowRule();
            flowRule.setResource("test");
            flowRule.setCount(20);
            flowRule.setGrade(RuleConstant.FLOW_GRADE_QPS);
            list.add(flowRule);
            FlowRuleManager.loadRules(list);
        }
    
    }

启动类配置限流，对test资源限流

ab工具访问http://localhost:8080/test

输出;

出错！！！
    Hello
    com.alibaba.csp.sentinel.slots.block.flow.FlowException
    出错！！！
    Hello
    com.alibaba.csp.sentinel.slots.block.flow.FlowException
    出错！！！

[https_github.com_alibaba_Sentinel_wiki_E4_BB_8B_E7_BB_8D]: https://github.com/alibaba/Sentinel/wiki/%E4%BB%8B%E7%BB%8D
[https_github.com_alibaba_Sentinel_wiki_Sentinel_E5_B7_A5_E4_BD_9C_E4_B8_BB_E6_B5_81_E7_A8_8B]: https://github.com/alibaba/Sentinel/wiki/Sentinel%E5%B7%A5%E4%BD%9C%E4%B8%BB%E6%B5%81%E7%A8%8B
[https_github.com_alibaba_Sentinel_wiki_E6_B5_81_E9_87_8F_E6_8E_A7_E5_88_B6]: https://github.com/alibaba/Sentinel/wiki/%E6%B5%81%E9%87%8F%E6%8E%A7%E5%88%B6
[https_github.com_alibaba_Sentinel_wiki_E7_86_94_E6_96_AD_E9_99_8D_E7_BA_A7]: https://github.com/alibaba/Sentinel/wiki/%E7%86%94%E6%96%AD%E9%99%8D%E7%BA%A7
[https_github.com_alibaba_Sentinel_blob_master_sentinel-demo_sentinel-demo-basic_src_main_java_com_alibaba_csp_sentinel_demo_degrade_RtDegradeDemo.java]: https://github.com/alibaba/Sentinel/blob/master/sentinel-demo/sentinel-demo-basic/src/main/java/com/alibaba/csp/sentinel/demo/degrade/RtDegradeDemo.java
[https_github.com_alibaba_Sentinel_wiki_E6_B3_A8_E8_A7_A3_E6_94_AF_E6_8C_81]: https://github.com/alibaba/Sentinel/wiki/%E6%B3%A8%E8%A7%A3%E6%94%AF%E6%8C%81