Spring Cloud Alibaba 03_使用 Sentinel 实现服务限流降级熔断

客官°小女子只卖身不卖艺 2022-12-16 13:10 297阅读 0赞

**Spring Cloud Alibaba 03\_使用 Sentinel 实现服务限流降级熔断**

**雪崩效应**

当服务A不可用时，服务B调用服务A的所有线程将处于阻塞状态，在高并发情况下，服务B中阻塞的线程越来越多，导致内存空间不足，致使服务B崩溃，同理，需要调用服务B的服务C也可能崩溃，这就是雪崩效应。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left]  
**解决方案：**

1.  设置线程超时释放
2.  设置服务限流
3.  设置熔断器Hystrix、Sentinel

**降级：** 系统将某些非必要功能关闭，只提供关键功能  
**限流：** 只接收系统能够承载的访问量  
**熔断：** 切断对某个故障服务的调用

--------------------

**Sentinel 实现服务限流**

*  **在 provider 中 添加 Sentinel 和 actuator 依赖：**

<dependency>
    	<groupId>com.alibaba.cloud</groupId>
    	<artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
    	<version>2.2.1.RELEASE</version>
    </dependency>
    <dependency>
    	<groupId>org.springframework.boot</groupId>
    	<artifactId>spring-boot-starter-actuator</artifactId>
    	<version>2.2.1.RELEASE</version>
    </dependency>

*  **在配置文件中暴露所有端点，并指定 sentinel 的 uri （sentinel 默认端口为8080）：**

spring:
      cloud:
        nacos:
          discovery:
            server-addr: localhost:8848
        sentinel:
          transport:
            dashboard: localhost:8080
      application:
        name: provider
    
    server:
      port: 8083
    
    # 暴露所有端点
    management:
      endpoints:
        web:
          exposure:
            include: '*'

*  **下载 Sentinel：[https://github.com/alibaba/Sentinel/releases][https_github.com_alibaba_Sentinel_releases]**
 *  **java -jar 启动 Sentinel，然后访问：[http://localhost:8080][http_localhost_8080] 进入控制台，登录用户名和密码都是 sentinel**
 *  **依次启动 nacos、sentinel、 provider 后，多次访问 provider 的 /index 接口，观察到如下图表：**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_center]

*  **点击 簇点链路 --> 点击 /index 接口的流控，显示如下弹窗：**

阈值类型选择QPS，单机阈值设为1  
即每秒钟只允许1次访问

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_center 1]

*  **再次短时间多次访问 /index 接口，当1s访问超过1次时，将会显示：Blocked by Sentinel (flow limiting)**

![在这里插入图片描述][20201020162318713.png_pic_left]  
**同时观察到以下图表：**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_center 2]  
  
  
**流控模式-关联模式**

*  **在 provider 中添加 /list 接口，编辑流控规则，点击高级选项，流控模式选择关联，关联资源中填写/list**

**此时当 /list 接口每秒访问超过1次时，/index 接口将会被限流（你闯祸我背锅）**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 1]  
  
  
**流控模式-链路模式**

**在 provider 中添加以下两个依赖：**

<dependency>
    	<groupId>com.alibaba.csp</groupId>
    	<artifactId>sentinel-core</artifactId>
    	<version>1.7.1</version>
    </dependency>
    <dependency>
    	<groupId>com.alibaba.csp</groupId>
    	<artifactId>sentinel-web-servlet</artifactId>
    	<version>1.7.1</version>
    </dependency>

**在配置文件中配置关闭 sentinel 的 filter 功能：**

spring:
      cloud:
        sentinel:
          filter:
            enabled: false

**FilterConfiguration 配置类：**

package com.blu.configuration;
    
    import com.alibaba.csp.sentinel.adapter.servlet.CommonFilter;
    import org.springframework.boot.web.servlet.FilterRegistrationBean;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @Configuration
    public class FilterConfiguration { 
    
        @Bean
        public FilterRegistrationBean registrationBean(){ 
            FilterRegistrationBean registrationBean = new FilterRegistrationBean();
            registrationBean.setFilter(new CommonFilter());
            //过滤所有的请求
            registrationBean.addUrlPatterns("/*");
            //关闭收敛功能，即可开放所有的链路
            registrationBean.addInitParameter(CommonFilter.WEB_CONTEXT_UNIFY,"false");
            registrationBean.setName("sentinelFilter");
            return registrationBean;
        }
    
    }

**在Service层添加test方法，并加上 @SentinelResource 注解：**

package com.blu.service;
    
    import com.alibaba.csp.sentinel.annotation.SentinelResource;
    import org.springframework.stereotype.Service;
    
    @Service
    public class ProviderService { 
    
        @SentinelResource("service-test")
        public void test(){ 
            System.out.println("test");
        }
    }

**在 Controller 层添加 test1和test2两个方法来调用Service层的test方法：**

@Autowired
    private ProviderService providerService;
    
    @GetMapping("/test1")
    public String test1(){ 
    	this.providerService.test();
        return "test1";
    }
    
    @GetMapping("/test2")
    public String test2(){ 
    	this.providerService.test();
        return "test2";
    }

**依次启动nacos、sentinel、 provider 后，设置以下流控规则：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 2]  
**频繁访问 /test1 接口，当QPS大于1时，将显示错误页面：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 3]  
**而频繁访问 /test2 接口皆正常：**  
![在这里插入图片描述][20201025150050639.png_pic_left]

**流控效果 - Warm Up（预热）**

**添加如下流控规则：**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 4]  
**当点击新增后，系统会在10s内缓慢地将 /index 接口的请求阈值升至3 QPS**

**流控效果-排队等待**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 5]

**服务降级-降级策略-RT**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 6]  
**当某个请求的响应时间超过1毫秒时，将进入准降级状态，在接下来的1s时间内如果连续5个请求的响应时间均超过1毫秒，将进入降级状态，持续时间为10秒**

**服务降级-降级策略-异常比例**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 7]  
**当请求出现异常的比例达到了20%，将进入降级状态，持续时间10s**

**服务降级-降级策略-异常数**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 8]  
**在1分钟内异常请求的次数达到5个，将进入降级状态，持续时间80秒（这里的降级持续时间一定要大于1分钟！）**

**热点规则**

**在Controller中添加如下方法：**

@GetMapping("/hot")
    @SentinelResource("controller-hot")
    public String hot(@RequestParam(value = "num1",required = false) Integer num1, @RequestParam(value = "num2",required = false) Integer num2){ 
    	return num1+"---"+num2;
    }

**请求示例：[http://localhost:8081/hot?num1=1&num2=2][http_localhost_8081_hot_num1_1_num2_2]**  
![在这里插入图片描述][20201025161033319.png_pic_left]  
**给 controller-hot 添加热点规则：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 9]  
**当请求参数中存在参数1（num1）时，QPS超过1将抛出异常：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 10]  
**在高级选项中，可设置参数例外值：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 11]  
**即：对参数1（num1）进行限流，阈值为1，但当num1为int类型，值为10时，限流阈值为1000**

**授权规则**

*  **在 Provider 中添加 RequestOriginParserDefinition 类：**

package com.blu.configuration;
    
    import com.alibaba.csp.sentinel.adapter.servlet.callback.RequestOriginParser;
    import org.springframework.util.StringUtils;
    
    import javax.servlet.http.HttpServletRequest;
    
    public class RequestOriginParserDefinition implements RequestOriginParser { 
        @Override
        public String parseOrigin(HttpServletRequest httpServletRequest) { 
            String name = httpServletRequest.getParameter("name");
            if (StringUtils.isEmpty(name)){ 
                throw new RuntimeException("name is null");
            }
            return name;
        }
    }

*  **编写 SentinelConfiguration 配置类使 RequestOriginParserDefinition 类生效：**

package com.blu.configuration;
    
    import com.alibaba.csp.sentinel.adapter.servlet.callback.WebCallbackManager;
    import org.springframework.context.annotation.Configuration;
    
    import javax.annotation.PostConstruct;
    
    @Configuration
    public class SentinelConfiguration { 
    
        @PostConstruct
        public void init(){ 
            WebCallbackManager.setRequestOriginParser(new RequestOriginParserDefinition());
        }
    
    }

**此时，访问不携带name参数将报错：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 12]  
![在这里插入图片描述][20201025174051328.png_pic_left]

*  **添加授权规则：**  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 13]  
    **此时，访问 /index 接口必须携带name参数，且参数值必须为admin**
 *  **修改授权规则：**  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 14]  
    **此时，访问 /index 接口必须携带name参数，且参数值不能为blu**![在这里插入图片描述][20201025174912865.png_pic_left]  
    ![在这里插入图片描述][20201025174826735.png_pic_left]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left]: /images/20221123/78e9f1d263c74ad6b57ec454605daae0.png
[https_github.com_alibaba_Sentinel_releases]: https://github.com/alibaba/Sentinel/releases
[http_localhost_8080]: http://localhost:8080
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/00c18b5716c0415a8f409eca208ddc10.png
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[20201020162318713.png_pic_left]: /images/20221123/2dc861d6433346ec83a5a6e430a212d0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_center 2]: /images/20221123/6b55d0ec96bc4bcb96b1203d90532b4d.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 1]: /images/20221123/1ff6609201e24b4a8e8255f94c4625e1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 2]: /images/20221123/2d10236bfdca42b59e8ff08d2e3ec667.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 3]: /images/20221123/14e66b743f8742d5a097d30e7741e4c0.png
[20201025150050639.png_pic_left]: /images/20221123/caf86c97f23549a894a089b4e151f79b.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 5]: /images/20221123/d18d3af2c86c4d1689bac426050370cc.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 6]: /images/20221123/ef74300d228a4945bda6d89b30cbee9f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 7]: /images/20221123/8f31de466dca46ea9f33afc041e7ad33.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 8]: /images/20221123/e8cbbe10621f4ca79c8683595b0ccffa.png
[http_localhost_8081_hot_num1_1_num2_2]: http://localhost:8081/hot?num1=1&num2=2
[20201025161033319.png_pic_left]: /images/20221123/c9e694d699a349eda4a72f21bcc2beac.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JMVV8xMTE_size_16_color_FFFFFF_t_70_pic_left 9]: /images/20221123/6387f3c3644141bf867b7496ab820aac.png
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[20201025174051328.png_pic_left]: /images/20221123/f5fff33462f3456097ad23f0498c219c.png
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[20201025174912865.png_pic_left]: /images/20221123/b05052e5c75c4e87956fa5b0c6cb2757.png
[20201025174826735.png_pic_left]: /images/20221123/62981256fac54b34a41bafed646c0aa7.png