[Sentinel 笔记] Sentinel的流量控制和降级

红太狼 2023-10-03 11:28 179阅读 0赞

**目录**

boot 配置 sentinel

介绍:

Sentinel 是面向分布式服务架构的流量控制组件，主要以流量为切入点，从流量控制、熔断降级、系统自适应保护等多个维度来帮助您保障微服务的稳定性。

**Sentinel 阿里下载地址:我这里是1.8.1版本**

**下载对应的文件下面 ,在地址栏输入cmd 然后 java -jar**

[sentinel-dashboard-1.8.1.jar][]**(jar包的全名称路径) 然后运行,默认端口应该是:8080**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70][]

![20210722091845982.png][]

**运行成功访问端口:8080,要注意是否会出现端口冲突**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 1][]

**下载地址:**

**[https://github.com/alibaba/Sentinel/releases][https_github.com_alibaba_Sentinel_releases]**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 2][]

运行成功的样子:

**登录的账号密码均为:sentinel**

**需要在boot项目里面配置相关sentinel的信息 ，在控制台对应接口加入一个注解:**

@SentinelResource(value="hi")  加入注解以后,运行项目访问接口,然后多次刷新sentinel 就能查看到 sentinel 就有对应接口相关信息了！！！

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 4][]

\--------------------------------

### **boot 配置 sentinel** ###

pom依赖:

>     
>     <dependency>
>         <groupId>com.alibaba.cloud</groupId>
>         <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
>         <version>2.1.0.RELEASE</version>
>     </dependency>

yml配置: 注意yml配置的空格约束

>     cloud:
>       sentinel:
>         transport:
>           dashboard: localhost:8080

控制台配置: @SentinelResource(value="hi")

@SentinelResource(value="hi")
        @RequestMapping("/hello")
        public String hello(){
    
            return "你好";
        }

配置以后的运行效果:

**先访问配置的接口:**

![20210722093211206.png][]

访问成功以后:

多次刷新sentinel 出现对应接口信息 ,这里你就可以进行相关配置了

,nacos 注册中心就是集成这种 好像！ 后面的自己去了解吧

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 5][]

**我们这里可以对它进行配置一个流控，点击流控按钮  
配置`QPS`为`1`**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 6][]

**点击新增后我们每秒都只能请求一次了  
多次请求多了则会被限流**

![20210722094843689.png][]

我们还可以定义我们受保护的资源  
简单来说，就是我们的代码块  
下面这段代码可以直接试着运行一下

package com.luodada;
    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 java.util.ArrayList;import java.util.List;/**
     * sentinel测试类
     *
     *  
     *  
     */public class SimpleSentinelTests {
    
    
    
         public static void main(String[] args) {
             // 配置规则.
        initFlowRules();
        while (true) {
            // 1.5.0 版本开始可以直接利用 try-with-resources 特性
            try (
    //                判断资源的名称 如果是HelloWorld 就进去
                    Entry entry = SphU.entry("HelloWorld")) {
                // 被保护的逻辑
                System.out.println("hello world");
            } catch (BlockException ex) {
                // 处理被流控的逻辑
                System.out.println("blocked!");
            }
        }
    }
    
    private static void initFlowRules() {
        List<FlowRule> rules = new ArrayList<>();
        FlowRule rule = new FlowRule();
        rule.setResource("HelloWorld");     //设置资源的名称
        rule.setGrade(RuleConstant.FLOW_GRADE_QPS);        //  设置流控的规则的以QPS为准，还有以线程为准
        rule.setCount(20);  //令牌   意思就是只能打印20次  HelloWorld信息
        rules.add(rule);
        FlowRuleManager.loadRules(rules);  //添加进流控规则管理中
    
    }
    
    }

输出结果: 展示20次 需要保护的资源！！

后面就是 被流控的逻辑了

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 7][]

我们除了使用`FlowRuleManager.loadRules`去配置资源流控规则以外，还可以直接在`sentinel`控制台进行配置

**在对应接口上面配置流控:**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 8][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 9][]

第二种流控异常: 通过后面的降级去处理

**下面截图里面的三段代码:**

若我们的应用使用了Spring AOP，我们需要通过配置的方式将 SentinelResourceAspect 注册为一个 Spring Bean：
    
    @Configurationpublic class SentinelAspectConfiguration {     @Bean
         public SentinelResourceAspect sentinelResourceAspect() {            return new SentinelResourceAspect();
         }
    }
    
    
    
    找个地方注入这个Bean以后
    我们在service实现类中写上这个注解
    package com.ruben.simplesentinel.service.impl;import com.alibaba.csp.sentinel.annotation.SentinelResource;import com.ruben.simplesentinel.service.IHelloWorldService;import org.springframework.stereotype.Service;/**
     * helloWorld业务层实现类
     *
     * @author <achao1441470436@gmail.com>
     * @since 2021/6/29 0029 22:44
     */@Servicepublic class HelloWorldServiceImpl implements IHelloWorldService {    @SentinelResource("HelloWorld")    @Override
        public void helloWorld() {        // 资源中的逻辑
            System.out.println("hello world");
        }
    
    }
    
    
    然后方法调用:
    package com.ruben.simplesentinel;import com.alibaba.csp.sentinel.annotation.SentinelResource;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 com.ruben.simplesentinel.service.IHelloWorldService;import org.junit.jupiter.api.Test;import org.springframework.boot.test.context.SpringBootTest;import javax.annotation.Resource;import java.util.ArrayList;import java.util.List;@SpringBootTestclass SimpleSentinelApplicationTests {    @Resource
        private IHelloWorldService helloWorldService;    @Test
        void contextLoads() {
            initFlowRules();        while (true) {
                helloWorldService.helloWorld();
            }
        }    private static void initFlowRules() {
            List<FlowRule> rules = new ArrayList<>();
            FlowRule rule = new FlowRule();
            rule.setResource("HelloWorld");
            rule.setGrade(RuleConstant.FLOW_GRADE_QPS);        // Set limit QPS to 20.
            rule.setCount(20);
            rules.add(rule);
            FlowRuleManager.loadRules(rules);
        }
    
    }
    
    可以看到在执行20次后抛出了java.lang.reflect.UndeclaredThrowableException
    并且是由我们com.alibaba.csp.sentinel.slots.block.flow.FlowException导致的

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 10][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 11][]

除了进行限流，我们还可以直接配置降级: 因为上面出现异常 我们就可以使用降级来 提高用户使用体验！！！

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 12][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 13][]

当上面代码抛出异常,, 我们使用降级以后,当我们请求几次后 :就不会再执行我们的方法抛出`NPE`了;，因为此时我们配置的服务降级生效

##  **通过配置`sentinel`限流与降级，提升了我们程序的健壮性，使得其不至于在高并发场景下压力过大,提供程序使用体验！** ##

\--------------------------------------------------------------------------------------------------

小知识总结:

java -Dserver.port=**`8000`**\-Dcsp.sentinel.dashboard.server=localhost:**`8000`**\-Dproject.name=sentinel-dashboard -jar sentinel-dashboard-1.8.1.jar

**命令详细  
这里`server.port=8000`表示在`8000端口启动`  
`csp.sentinel.dashboard.server`指定指定控制台地址和端口  
`project.name`指定应用名  
更多的参数参见 启动参数文档。**

**我这里创建的镜像 是使用的aliyun的**

![2021072209382028.png][]

创建sentinel 和 web 依赖:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70 14][]

> spring:  
> cloud:  
> sentinel:  
> transport:  
> \# Sentinel 控制台地址  
> dashboard: localhost:9000  
> \# 如果有多套网络，又无法正确获取本机IP，则需要使用下面的参数设置当前机器可被外部访问的IP地址，供admin控制台使用  
> \# client-ip:  
> \# 取消Sentinel控制台懒加载  
> \# 默认情况下 Sentinel 会在客户端首次调用的时候进行初始化，开始向控制台发送心跳包  
> \# 配置 sentinel.eager=true 时，取消Sentinel控制台懒加载功能  
> eager: true  
> filter:  
> \# 配置启用拦截器  
> enabled: true  
> \# 配置拦截器路径  
> url-patterns: /\*\*

结合阿超

[sentinel-dashboard-1.8.1.jar]: https://github.com/alibaba/Sentinel/releases/download/1.8.2/sentinel-dashboard-1.8.2.jar
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20210721224035284.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NxTDUyMGxU,size_16,color_FFFFFF,t_70
[20210722091845982.png]: https://img-blog.csdnimg.cn/20210722091845982.png
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[https_github.com_alibaba_Sentinel_releases]: https://github.com/alibaba/Sentinel/releases
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