一、 sentinel是什么？

1.概念：

分布式服务架构的流量治理组件。

2.sentinel有什么作用？

2.1 流控：QPS、线程数

2.2 熔断降级：降级-->熔断策略、时长、请求数等

2.3 授权：黑白名单

2.4 系统自适应过载保护

提供保护机制让系统入口流量与负载达到平衡，使得系统在尽可能处理最多的请求

2.5 热点流量防护

二、 sentinel如何应用于项目中？

1.引入sentinel及持久化到nacos依赖

<dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId> </dependency> <!-- Sentinel规则持久化至Nacos配置 --> <dependency> <groupId>com.alibaba.csp</groupId> <artifactId>sentinel-datasource-nacos</artifactId> </dependency>

2.配置

2.1 sentinel及nacos

spring: cloud: sentinel: enabled: true eager: true # 取消控制台懒加载，项目启动即连接Sentinel transport: client-ip: localhost dashboard: localhost:8080 datasource: ds: nacos: server-addr: http://cloud.lebao.site:8848 dataId: ams-admin-degrade-rules groupId: DEFAULT_GROUP data-type: json rule-type: flow

2.2 在nacos创建限流规则配置文件：

ams-admin-degrade-rules

[ { "resource": "/hello", "limitApp": "default", "grade": 1, "count": 5, "strategy": 0, "controlBehavior": 0, "clusterMode": false } ]

3.添加sentinel公共模块

3.1 创建网关过滤器PortalFilter

package com.ams.gateway.security; import lombok.RequiredArgsConstructor; import lombok.SneakyThrows; import lombok.extern.slf4j.Slf4j; import org.springframework.beans.factory.annotation.Value; import org.springframework.cloud.gateway.filter.GatewayFilterChain; import org.springframework.cloud.gateway.filter.GlobalFilter; import org.springframework.core.Ordered; import org.springframework.http.server.reactive.ServerHttpRequest; import org.springframework.stereotype.Component; import org.springframework.web.server.ServerWebExchange; import reactor.core.publisher.Mono; /** * @description：请求头中添加当前服务名称 */ @Component @Slf4j @RequiredArgsConstructor public class PortalFilter implements GlobalFilter, Ordered { @Value("${spring.application.name}") private String applicationName; @SneakyThrows @Override public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) { ServerHttpRequest request = exchange.getRequest().mutate() .header("serviceName", applicationName) .build(); exchange = exchange.mutate().request(request).build(); return chain.filter(exchange); } @Override public int getOrder() { return -1; } }

3.2 创建sentinel来源解析器RequestOriginParserDefinition

package com.ams.common.web.sentinel; import com.alibaba.csp.sentinel.adapter.spring.webmvc.callback.RequestOriginParser; import org.springframework.stereotype.Component; import org.springframework.util.StringUtils; import javax.servlet.http.HttpServletRequest; /** * @description：通过HttpServletRequest获取服务名 */ @Component public class RequestOriginParserDefinition implements RequestOriginParser { // 获取调用方标识信息并返回 @Override public String parseOrigin(HttpServletRequest request) { String serviceName = request.getHeader("serviceName"); StringBuffer url = request.getRequestURL(); if (url.toString().endsWith("favicon.ico")) { // 浏览器会向后台请求favicon.ico图标 return serviceName; } if (StringUtils.isEmpty(serviceName)) { throw new IllegalArgumentException("serviceName must not be null"); } return serviceName; } }

3.3 创建BlockExceptionHandler 阻塞异常处理器

package com.ams.common.web.sentinel; import cn.hutool.http.HttpStatus; import com.alibaba.csp.sentinel.adapter.spring.webmvc.callback.BlockExceptionHandler; import com.alibaba.csp.sentinel.slots.block.BlockException; import com.alibaba.csp.sentinel.slots.block.authority.AuthorityException; import com.alibaba.csp.sentinel.slots.block.degrade.DegradeException; import com.alibaba.csp.sentinel.slots.block.flow.FlowException; import com.ams.common.result.R; import com.ams.common.result.ResultCode; import com.fasterxml.jackson.databind.ObjectMapper; import org.springframework.stereotype.Component; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @description：捕获流控、降级、未授权异常 */ @Component public class DefaultBlockExceptionHandler implements BlockExceptionHandler { @Override public void handle(HttpServletRequest request, HttpServletResponse response, BlockException e) throws Exception { response.setStatus(HttpStatus.HTTP_OK); response.setCharacterEncoding("UTF-8"); response.setContentType("application/json;charset=utf-8"); ObjectMapper objectMapper = new ObjectMapper(); // 流控 if (e instanceof FlowException) { objectMapper.writeValue(response.getWriter(), R.failed(ResultCode.FLOW_LIMITING)); // 降级 } else if (e instanceof DegradeException) { objectMapper.writeValue(response.getWriter(), R.failed(ResultCode.DEGRADATION)); // 未授权 } else if (e instanceof AuthorityException) { objectMapper.writeValue(response.getWriter(), R.failed(ResultCode.SERVICE_NO_AUTHORITY)); } } }

3.4 下载安装sentinel面板添加设置流程、降级、授权规则等

3.4.1 流控

配置规则

3.4.2 降级

新建规则

3.4.2 授权

设置规则

参考链接

三、Sentinel插槽工作原理

关于插槽详细介绍：https://zhuanlan.zhihu.com/p/64786381

<hr style=" border:solid; width:100px; height:1px;" color=#000000 size=1">

随心所往，看见未来。Follow your heart，see night！<br/>

欢迎点赞、关注、留言，收藏及转发，一起学习、交流！