SpringCloud Alibaba - Sentinel篇

柔情只为你懂 2024-03-02 10:21 108阅读 0赞

## 一、Sentinel快速入门 ##

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

![image-20230920210017106][]

> Sentinel官网地址：https://sentinelguard.io/zh-cn/index.html

> Sentinel项目地址：https://github.com/alibaba/Sentinel

Sentinel是阿里巴巴开源的一款微服务流量治理组件，主要以流量为切入点，从流量限流、熔断降级、系统负载保护等多个维度来帮助开发者保障微服务的稳定性。（对标产品：Springcloud Hystrix 豪猪哥）

Sentinel分为两个部分:

*  **核心库（Java客户端）**：该jar包不依赖任何框架，能够运行于 Java 8 及以上版本，同时对 Dubbo / Spring Cloud 等框架也有较好的支持。
 *  **控制台（Dashboard）**：相当于是Sentinel框架的管理中心，可以通过图形化界面对Sentinel进行配置、监控（可以对服务的流量、请求、响应等指标进行监控）等操作，从而更好地保障应用的稳定性和可靠性。

![image-20230920213830678][]

两款熔断框架对比：

<table> 
 <thead> 
  <tr> 
   <th align="center">功能</th> 
   <th align="center">Sentinel</th> 
   <th align="center">Hystrix（豪猪哥）</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">线程隔离</td> 
   <td align="center">信号量隔离</td> 
   <td align="center">线程池隔离/信号量隔离</td> 
  </tr> 
  <tr> 
   <td align="center">熔断策略</td> 
   <td align="center">基于慢调用比例或异常比例</td> 
   <td align="center">基于异常比例</td> 
  </tr> 
  <tr> 
   <td align="center">限流</td> 
   <td align="center">基于QPS,支持流量整形</td> 
   <td align="center">有限的支持</td> 
  </tr> 
  <tr> 
   <td align="center">Fallback</td> 
   <td align="center">支持</td> 
   <td align="center">支持</td> 
  </tr> 
  <tr> 
   <td align="center">控制台</td> 
   <td align="center">开箱即用，可配置规则、查看秒级监控、机器发现等</td> 
   <td align="center">不完善</td> 
  </tr> 
  <tr> 
   <td align="center">配置方式</td> 
   <td align="center">基于控制台，重启后失效</td> 
   <td align="center">基于注解或配置文件，永久生效</td> 
  </tr> 
 </tbody> 
</table>

### 1. 启动sentinel-dashboard控制台 ###

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

> 通过可视化更方便操作Sentinel。

1、下载sentinel-dashboard的jar包：https://github.com/alibaba/Sentinel/releases/tag/1.8.6

![image-20230921001906722][]

2、使用命令行运行jar包的方式启动控制台：（或者构建镜像丢到容器中启动）

java -Dserver.port=8090 -Dcsp.sentinel.dashboard.server=localhost:8090 -Dproject.name=sentinel-dashboard -jar sentinel-dashboard-1.8.6.jar

参数介绍：

*  `-Dserver.port=8090`：指定Sentinel控制台程序的端口为8090。
 *  `-Dcsp.sentinel.dashboard.server=localhost:8090`：Sentinel控制台的访问地址，客户端会自动向该地址发送心跳包。
 *  `-Dproject.name=sentinel-dashboard`：指定Sentinel控制台程序显示的名称。
 *  文档地址：https://github.com/alibaba/Sentinel/wiki/%E5%90%AF%E5%8A%A8%E9%85%8D%E7%BD%AE%E9%A1%B9

![image-20230921004704830][]

3、访问sentinel的控制台：http://localhost:8090/，默认账号/密码：都是sentinel。

![image-20230921005003769][]

登录成功后，便可查看控制台内部信息，默认会监控sentinel-dashboard服务本身：

![image-20230921005247618][]

![image-20230921005457889][]

![image-20230921005524797][]

### 2. 构建微服务环境 ###

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

数据库准备：

CREATE DATABASE cloud_demo DEFAULT CHARACTER SET utf8mb4;
    
    use cloud_demo;
    
    DROP TABLE IF EXISTS `tb_user`;
    
    CREATE TABLE `tb_user`  (
      `id` bigint(20) NOT NULL AUTO_INCREMENT,
      `username` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '收件人',
      `address` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '地址',
      PRIMARY KEY (`id`) USING BTREE,
      UNIQUE INDEX `username`(`username`) USING BTREE
    ) ENGINE = InnoDB AUTO_INCREMENT = 109 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;
    
    INSERT INTO `tb_user` VALUES (1, '潘掌柜', '黑龙江省牡丹江市');
    INSERT INTO `tb_user` VALUES (2, '文二狗', '陕西省西安市');
    INSERT INTO `tb_user` VALUES (3, '华沉鱼', '湖北省十堰市');
    INSERT INTO `tb_user` VALUES (4, '张必沉', '天津市');
    INSERT INTO `tb_user` VALUES (5, '郑爽爽', '辽宁省沈阳市大东区');
    INSERT INTO `tb_user` VALUES (6, 'kunkun', '山东省青岛市');
    
    
    DROP TABLE IF EXISTS `tb_order`;
    
    CREATE TABLE `tb_order`  (
      `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '订单id',
      `user_id` bigint(20) NOT NULL COMMENT '用户id',
      `name` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '商品名称',
      `price` bigint(20) NOT NULL COMMENT '商品价格',
      `num` int(10) NULL DEFAULT 0 COMMENT '商品数量',
      PRIMARY KEY (`id`) USING BTREE,
      UNIQUE INDEX `username`(`name`) USING BTREE
    ) ENGINE = InnoDB AUTO_INCREMENT = 109 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;
    
    INSERT INTO `tb_order` VALUES (101, 1, 'Apple 苹果 iPhone 12 ', 699900, 1);
    INSERT INTO `tb_order` VALUES (102, 2, '雅迪 yadea 新国标电动车', 209900, 1);
    INSERT INTO `tb_order` VALUES (103, 3, '骆驼（CAMEL）休闲运动鞋女', 43900, 1);
    INSERT INTO `tb_order` VALUES (104, 4, '小米10 双模5G 骁龙865', 359900, 1);
    INSERT INTO `tb_order` VALUES (105, 5, 'OPPO Reno3 Pro 双模5G 视频双防抖', 299900, 1);
    INSERT INTO `tb_order` VALUES (106, 6, '美的（Midea) 新能效 冷静星II ', 544900, 1);
    INSERT INTO `tb_order` VALUES (107, 2, '西昊/SIHOO 人体工学电脑椅子', 79900, 1);
    INSERT INTO `tb_order` VALUES (108, 3, '梵班（FAMDBANN）休闲男鞋', 31900, 1);

![image-20230921020130649][]

#### 2.1 创建父工程 ####

> springboot版本2.7.12，springcloud版本2021.0.3。

创建maven工程，删除src目录，并向pom文件中引入一些依赖：

![image-20230921011829295][]

![image-20230921012711687][]

<?xml version="1.0" encoding="UTF-8"?>
    <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>cn.z3inc</groupId>
        <artifactId>sentinel-demo</artifactId>
        <packaging>pom</packaging>
        <version>1.0</version>
    
        
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.7.12</version>
            <relativePath/> 
        </parent>
    
        <properties>
            <maven.compiler.source>8</maven.compiler.source>
            <maven.compiler.target>8</maven.compiler.target>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <org.projectlombok.version>1.18.20</org.projectlombok.version>
            <spring-cloud.version>2021.0.3</spring-cloud.version>
            <spring-cloud-alibaba.version>2021.0.4.0</spring-cloud-alibaba.version>
            <mybatis-plus.version>3.4.3</mybatis-plus.version>
            <hutool.version>5.8.11</hutool.version>
            <mysql.version>8.0.23</mysql.version>
        </properties>
    
        
        <dependencyManagement>
            <dependencies>
                
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                
                <dependency>
                    <groupId>com.alibaba.cloud</groupId>
                    <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                    <version>${spring-cloud-alibaba.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                
                <dependency>
                    <groupId>mysql</groupId>
                    <artifactId>mysql-connector-java</artifactId>
                    <version>${mysql.version}</version>
                </dependency>
                
                <dependency>
                    <groupId>com.baomidou</groupId>
                    <artifactId>mybatis-plus-boot-starter</artifactId>
                    <version>${mybatis-plus.version}</version>
                </dependency>
                
                <dependency>
                    <groupId>cn.hutool</groupId>
                    <artifactId>hutool-all</artifactId>
                    <version>${hutool.version}</version>
                </dependency>
            </dependencies>
        </dependencyManagement>
        <dependencies>
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>${org.projectlombok.version}</version>
            </dependency>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
       <build>
        <plugins>
            
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <configuration>
                    <skipTests>true</skipTests>
                </configuration>
            </plugin>
        </plugins>
    </build>
        
    </project>

#### 2.2 创建用户微服务 ####

1、创建用户模块

![image-20230921013420839][]

2、引入依赖：

3、编写application.yml文件配置：

server:
      port: 9001
    
    spring:
      application:
        name: user-service #服务名称
      cloud:
        nacos:
          # nacos注册中心配置
          discovery:
            server-addr: 127.0.0.1:8848 #nacos服务器地址
      # 数据库配置
      datasource:
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/cloud_demo?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&serverTimezone=Asia/Shanghai
        username: root
        password: 123456
    
    # mp配置
    mybatis-plus:
      mmapper-locations: classpath:mapper/*.xml #mapper配置文件存放路径
      type-aliases-package: cn.z3inc.user.pojo # 类型别名（实体类所在包）
      configuration:
        log-impl: org.apache.ibatis.logging.stdout.StdOutImpl  #配置标准sql输出
        map-underscore-to-camel-case: true #开启驼峰映射
    
    #日志级别
    logging:
      level:
        cn.z3inc: debug
      pattern:
        dateformat: MM-dd HH:mm:ss:SSS # 格式化输出日期

4、编写启动类：

@SpringBootApplication
    @MapperScan("cn.z3inc.user.mapper")
    public class UserServiceApplication {
        
        public static void main(String[] args) {
        
            SpringApplication.run(UserServiceApplication.class, args);
        }
    }

5、编写业务：

实体类：

package cn.z3inc.user.pojo;
    
    import lombok.Data;
    
    @Data
    public class User {
        private Long id;
        private String username;
        private String address;
    }

mapper接口：

package cn.z3inc.user.mapper;
    
    import cn.z3inc.user.pojo.User;
    import com.baomidou.mybatisplus.core.mapper.BaseMapper;
    import org.apache.ibatis.annotations.Mapper;
    
    @Mapper
    public interface UserMapper extends BaseMapper<User> {
        
        
    }

service接口：

package cn.z3inc.user.service;
    
    import cn.z3inc.user.pojo.User;
    import com.baomidou.mybatisplus.extension.service.IService;
    
    public interface UserService extends IService<User> {
        
    }

package cn.z3inc.user.service.impl;
    
    import cn.z3inc.user.mapper.UserMapper;
    import cn.z3inc.user.pojo.User;
    import cn.z3inc.user.service.UserService;
    import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
    import org.springframework.stereotype.Service;
    
    @Service
    public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
        
    }

controller:

package cn.z3inc.user.controller;
    
    import cn.z3inc.user.pojo.User;
    import cn.z3inc.user.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
    
    @RestController
    @RequestMapping("/user")
    public class UserController {
        
    
        @Autowired
        private UserService userService;
    
        /**
         * 根据ID获取用户信息
         *
         * @param id 用户ID
         * @return
         */
        @GetMapping("/{id}")
        public User findById(@PathVariable("id") Long id) {
        
            return userService.getById(id);
        }
    
        /**
         * 修改用户信息
         *
         * @param user 用户信息
         */
        @PutMapping("/update")
        public void updateUser(@RequestBody User user) {
        
            userService.updateById(user);
        }
    
        /**
         * 根据ID删除用户
         *
         * @param id
         * @return
         */
        @DeleteMapping("/{id}")
        public void deleteUser(@PathVariable("id") Long id) {
        
            userService.removeById(id);
        }
    
        /**
         *  新增用户
         * @param user
         */
        @PostMapping("/save")
        public void saveUser(@RequestBody User user) {
        
            userService.save(user);        
        }
    }

![image-20230921153653979][]

6、启动nacos、用户微服务测试

.\startup.cmd -m standalone

![image-20230921102040129][]

![image-20230921154742489][]

#### 2.3 创建订单微服务 ####

1、创建订单模块

![image-20230921155433895][]

2、引入依赖：

<?xml version="1.0" encoding="UTF-8"?>
    <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>
        <parent>
            <groupId>cn.z3inc</groupId>
            <artifactId>sentinel-demo</artifactId>
            <version>1.0</version>
        </parent>
    
        <artifactId>order-service</artifactId>
    
        <properties>
            <maven.compiler.source>8</maven.compiler.source>
            <maven.compiler.target>8</maven.compiler.target>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        </properties>
    
        <dependencies>
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-loadbalancer</artifactId>
            </dependency>
            
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>
            
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
            </dependency>
            
            <dependency>
                <groupId>cn.hutool</groupId>
                <artifactId>hutool-all</artifactId>
            </dependency>
        </dependencies>
    
        
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    </project>

3、编写application.yml配置：

server:
      port: 9001
    
    spring:
      application:
        name: user-service #服务名称
      cloud:
        nacos:
          # nacos注册中心配置
          discovery:
            server-addr: 127.0.0.1:8848 #nacos服务器地址
      # 数据库配置
      datasource:
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/cloud_demo?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&serverTimezone=Asia/Shanghai
        username: root
        password: 123456
    
    # mp配置
    mybatis-plus:
      mmapper-locations: classpath:mapper/*.xml #mapper配置文件存放路径
      type-aliases-package: cn.z3inc.order.pojo # 类型别名（实体类所在包）
      configuration:
        log-impl: org.apache.ibatis.logging.stdout.StdOutImpl  #配置标准sql输出
        map-underscore-to-camel-case: true #开启驼峰映射
      global-config:
        db-config:
          id-type: auto # 主键策略
          table-prefix: tb_ # 表名前缀配置
    
    #日志级别
    logging:
      level:
        cn.z3inc: debug
      pattern:
        dateformat: MM-dd HH:mm:ss:SSS # 格式化输出日期

4、编写启动类：

package cn.z3inc.order;
    
    import org.mybatis.spring.annotation.MapperScan;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    
    
    @EnableFeignClients(basePackages = "cn.z3inc.order.feign") //开启feign远程调用
    @SpringBootApplication
    @MapperScan("cn.z3inc.order.mapper")
    public class OrderServiceApplication {
        
        public static void main(String[] args) {
        
            SpringApplication.run(OrderServiceApplication.class, args);
        }
    }

5、编写业务：

实体类：

//用户实体
    @Data
    public class User {
        
        private Long id;
        private String username;
        private String address;
    }
    
    // 订单实体
    @Data
    public class Order {
        
        private Long id;
        private String name;
        private Long price;
        private Integer num;
        private Long userId;
        @TableField(exist = false) // 排除数据表中不存在的字段
        private User user;
    }

mapper接口：

package cn.z3inc.order.mapper;
    
    import cn.z3inc.order.pojo.Order;
    import com.baomidou.mybatisplus.core.mapper.BaseMapper;
    import org.apache.ibatis.annotations.Mapper;
    
    @Mapper
    public interface OrderMapper extends BaseMapper<Order> {
        
    
    }

service接口：

package cn.z3inc.order.service;
    
    import cn.z3inc.order.pojo.Order;
    import com.baomidou.mybatisplus.extension.service.IService;
    
    public interface OrderService extends IService<Order> {
        
        //根据id查订单
        Order findById(Long id);
    }

feign接口：

package cn.z3inc.order.feign;
    
    import cn.z3inc.order.pojo.User;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PathVariable;
    
    /**
     *  用户服务Feign接口
     */
    @FeignClient("user-service")//指定要调用的服务名称
    public interface UserClient {
        
    
        /*
            主要是基于SpringMVC的注解来声明远程调用的信息，比如：
                - 服务名称：userservice
                - 请求方式：GET
                - 请求路径：/user/{id}
                - 请求参数：Long id
                - 返回值类型：User
         */
    
        // 定义远程调用方法
        // 通过id查用户
        @GetMapping("/user/{id}") //调用对应controller的方法路径
        User findById(@PathVariable("id") Long id);// @PathVariable注解一定要指定参数名称,否则会报错
    }

service接口实现类：

@Service
    public class OrderServiceImpl extends ServiceImpl<OrderMapper, Order> implements OrderService {
        
    
        @Autowired
        private UserClient userClient;
    
        @Override
        public Order findById(Long id) {
        
            Order order = super.getById(id);
            User user = userClient.findById(order.getUserId());//微服务远程调用
            order.setUser(user);
            return order;
        }
    }

controller:

package cn.z3inc.order.controller;
    
    import cn.z3inc.order.pojo.Order;
    import cn.z3inc.order.service.OrderService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
    
    @RestController
    @RequestMapping("/order")
    public class OrderController {
        
    
        @Autowired
        private OrderService orderService;
    
        @GetMapping("/{orderId}")
        public Order findById(@PathVariable("orderId") Long orderId) {
        
            return orderService.findById(orderId);
        }
    }

6、测试：

![image-20230921163715671][]

#### 2.4 搭建网关微服务 ####

1、创建网关模块

![image-20230921164143848][]

2、引入依赖：

<dependencies>
        
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>
        
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
    </dependencies>

3、修改application.yml配置：

server:
      port: 10010 # 网关的服务端口
    spring:
      application:
        name: gateway # 服务名称
      cloud:
        nacos:
          server-addr: localhost:8848 # nacos服务地址
        # 网关的配置
        gateway:
          # 跨域配置
          globalcors:
            cors-configurations:
              '[/**]':
                allowed-origin-patterns: "*"
                allowed-headers: "*"
                allow-credentials: true
                allowed-methods:
                  - GET
                  - POST
                  - DELETE
                  - PUT
                  - OPTION
          # 网关路由配置        
          routes: 
            - id: user-service # 路由id    
              uri: lb://user-service # 路由地址
              predicates: # 路由断言(匹配规则)
                - Path=/user/** 
            - id: order-service
              uri: lb://order-service
              predicates:
                - Path=/order/**

4、编写启动类：

package cn.z3inc.gateway;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    public class GatewayApplication {
        
        public static void main(String[] args) {
        
            SpringApplication.run(GatewayApplication.class, args);
        }
    }

![image-20230921202520666][]

5、测试：

![image-20230921202050740][]

![image-20230921202210196][]

### 3. 整合Sentinel ###

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

> 向订单微服中引入sentinel依赖，并连接sentinel-dashboard控制台进行监控。

1、引入sentinel依赖：

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

2、修改订单服务的application.yml文件，添加sentinel控制台配置：

spring:
      cloud: 
        sentinel:
          transport:
            dashboard: localhost:8090 #控制台地址
          http-method-specify: true #开启请求方式前缀

![image-20230922212832817][]

3、重启订单微服务

4、访问订单微服务接口：http://localhost:9002/order/102

5、访问sentinel-dashboard控制台，查看订单服务请求资源：http://localhost:8090

![image-20230922113918905][]

![image-20230922113445998][]

簇点链路：就是项目内的调用链路。链路中被Sentinel监控的每个接口就是一个资源。默认情况下Sentinel会监控SpringMVC的每一个Endpoint(http接口)。限流、熔断等都是针对簇点链路中的资源设置的，而资源名默认就是接口的请求路径。

## 二、请求限流 ##

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

请求限流：限制访问接口的请求的并发量，避免服务因流量激增出现故障。

也是在sentinel控制台中配置，点击指定簇点链路后面的流控按钮，便可做限流处理：

![image-20230922120334138][]

![image-20230922120746025][]

使用 JMeter做压测：

（1）为测试计划创建线程组

![image-20230922124550510][]

![image-20230922125347750][]

（2）为线程组添加http取样器：

![image-20230922125853615][]

![image-20230922130155922][]

（3）为http取样器添加监听报告：

![image-20230922130423316][]

（4）为http取样器添加查看结果树：

![image-20230922130624205][]

（5）执行测试

![image-20230922131029049][]

![image-20230922131235248][]

![image-20230922132722842][]

最后控制台查看监控结果：

![image-20230922131159127][]

可以看出这个接口，通过的QPS为6，拒绝的QPS为4，符合我们的预期。

## 三、线程隔离 ##

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

限流可以降低服务器压力，尽量减少因并发流量引起的服务故障的概率，但并不能完全避免服务故障。一旦某个服务出现故障，我们必须隔离对这个服务的调用，避免发生雪崩。

线程隔离：也叫做舱壁模式，模拟船舱隔板的防水原理。通过限定每个业务使用的线程数量，将故障业务隔离，避免故障扩散。（好处：即使服务崩了损失一部分线程，也不会影响到整个 tomcat 的资源）

![image-20230922134001388][]

### 1. OpenFeign整合Sentinel ###

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

> 对订单服务的FeignClient接口做线程隔离。

修改订单服务的application.yml文件，配置开启Feign的sentinel功能：

feign:
      sentinel:
        enabled: true # 开启feign对sentinel的支持

![image-20230922135021576][]

重启订单服务，可以看到查询用户的FeignClient自动变成了一个簇点资源：

![image-20230922135404445][]

### 2. 配置线程隔离 ###

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

给查询用户feign接口的簇点资源配置并发线程数：（最多使用5个线程）

![image-20230922140117810][]

![image-20230922135836861][]

![image-20230922200857542][]

执行JMeter测试脚步，每秒发送100个请求:

![image-20230922140908719][]

测试结果如下：

![image-20230922195816752][]

## 四、服务熔断 ##

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

服务熔断：由 **断路器** 统计请求的异常比例或慢调用比例，如果超出阈值则会 **熔断** 该业务，则拦截该接口的请求。熔断期间，所有请求快速失败，全都走fallback降级逻辑，避免影响到当前服务。（Hystrix豪猪哥的做法：如果feign接口调不通，那就走feign接口实现类的逻辑，避免服务雪崩）

![image-20230923144019242][]

### 1. 编写降级逻辑 ###

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

> 跟豪猪哥的用法类似。

触发限流或熔断后的请求不一定要直接报错，也可以返回一些默认数据或者友好提示，用户体验会更好。

通常为FeignClient编写失败后的降级逻辑有两种方式：

*  方式一：FallbackClass,无法对远程调用的异常做处理。
 *  方式二：FallbackFactory,可以对远程调用的异常做处理（推荐使用）。

1、为订单服务的UserClient定义降级处理类，实现FallbackFactory接口。

package cn.z3inc.order.fallback;
    
    import cn.z3inc.order.feign.UserClient;
    import cn.z3inc.order.pojo.User;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.cloud.openfeign.FallbackFactory;
    
    /**
     * UserClient降级处理类
     *
     */
    @Slf4j
    public class UserClientFallback implements FallbackFactory<UserClient> {
        
    
        // 定义userclient降级逻辑
        @Override
        public UserClient create(Throwable cause) {
        
            return new UserClient(){
        
                @Override
                public User findById(Long id) {
         
                    log.error("远程调用UserClient#findById方法出现异常，参数：{}", id, cause);
                    return new User();
                }
            };
        }
    }

![image-20230923151519698][]

2、创建一个配置类，把UserClientFallback注册为一个Bean：

package cn.z3inc.order.config;
    
    import cn.z3inc.order.fallback.UserClientFallback;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.context.annotation.Bean;
    
    @Slf4j
    public class DefaultFeignConfig {
        
        
        @Bean
        public UserClientFallback userClientFallback() {
        
            return new UserClientFallback();
        }
    }

3、在UserClient中配置刚才创建的降级处理类：

/**
     *  用户服务Feign接口
     */
    @FeignClient(value = "user-service", //指定要调用的服务名称
            configuration = DefaultFeignConfig.class, // 指定Feign的配置类
            fallbackFactory = UserClientFallback.class // 指定回退工厂类
    )
    public interface UserClient {

![image-20230923152127413][]

4、重启订单服务，将用户服务停掉&测试：

![image-20230923152307420][]

### 2. 服务熔断 ###

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

当远程调用的服务挂掉后，直接走降级逻辑，避免影响到当前服务。也就是将feign接口进行**熔断**。当远程调用服务恢复正常后，再允许调用该接口。这其实就是**断路器**的工作模式了。

Sentinel中的断路器不仅可以统计某个接口的**慢请求比例**，还可以统计**异常请求比例**。当这些比例超出阈值时，就会**熔断**该接口，即拦截访问该接口的一切请求，降级处理；当该接口恢复正常时，再放行对于该接口的请求。  
断路器的工作状态切换有一个状态机来控制：  
![47383fb3c199772b2fafc3e1a42c3818.jpeg][]  
状态机包括三个状态：

*  **closed**：关闭状态，断路器放行所有请求，并开始统计异常比例、慢请求比例。超过阈值则切换到open状态
 *  **open**：打开状态，服务调用被**熔断**，访问被熔断服务的请求会被拒绝，快速失败，直接走降级逻辑。Open状态持续一段时间后会进入half-open状态
 *  **half-open**：半开状态，放行一次请求，根据执行结果来判断接下来的操作。
    
     *  请求成功：则切换到closed状态
     *  请求失败：则切换到open状态

我们可以在控制台通过点击簇点链路后的`熔断`按钮来配置熔断策略：(持久化需要写到nacos配置文件里)

![image-20230923153302326][]

![image-20230923153424668][]

这种是按照慢调用比例来做熔断，上述配置的含义是：

*  RT超过200毫秒的请求调用就是慢调用
 *  统计最近1000ms内的最少5次请求，如果慢调用比例不低于0.5，则触发熔断
 *  熔断持续时长20s

使用jmeter测试：

![image-20230923154511253][]

![image-20230923154811934][]

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