阶段七模块一分布式锁实现商品秒杀

2021/4/8 10:08:40

编程Tag： 模块 spring 秒杀 id int 分布式 public -- product

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内容输出来源：拉钩教育Java就业训练营

锁：我们在多线程中接触过，作用就是让当前的资源不会被其他线程访问！

在zookeeper中使用传统的锁引发的 “羊群效应” ：1000个人创建节点，只有一个人能成功，999人需要等待！

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避免“羊群效应”，zookeeper采用分布式锁

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所有请求进来，在/lock下创建 临时顺序节点 ，放心，zookeeper会帮你编号排序
判断自己是不是/lock下最小的节点
1. 是，获得锁（创建节点）
2. 否，对前面小我一级的节点进行监听
获得锁请求，处理完业务逻辑，释放锁（删除节点），后一个节点得到通知（比你年轻的死了，你成为最年轻的了）
重复步骤2

实现步骤

1 初始化数据库

-- 商品表
create table product(
    id int primary key auto_increment, -- 商品编号
    product_name varchar(20) not null, -- 商品名称
    stock int not null, -- 库存
    version int not null -- 版本
)
insert into product (product_name,stock,version) values('锦鲤-清空购物车-大奖',5,0)

-- 订单表
create table `order`(
    id varchar(100) primary key, -- 订单编号
    pid int not null, -- 商品编号
    userid int not null -- 用户编号
)

2 搭建工程

工程构造

实体类Order和Product自行创建

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<packaging>war</packaging>
    <properties>
        <spring.version>5.2.7.RELEASE</spring.version>
    </properties>

    <dependencies>
        <!-- Spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!-- Mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>2.0.5</version>
        </dependency>
        <!-- 连接池 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.10</version>
        </dependency>
        <!-- 数据库 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.20</version>
        </dependency>
        <!-- junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <!-- maven内嵌的tomcat插件 -->
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <!-- 目前apache只提供了tomcat6和tomcat7两个插件 -->
                <artifactId>tomcat7-maven-plugin</artifactId>
                <configuration>
                    <port>8001</port>
                    <path>/</path>
                </configuration>
                <executions>
                    <execution>
                        <!-- 打包完成后,运行服务 -->
                        <phase>package</phase>
                        <goals>
                            <goal>run</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

mybatis配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 后台的日志输出：针对开发者-->
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
</configuration>

spring配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd">
    <!-- 1.扫描包下的注解 -->
    <context:component-scan base-package="controller,service,mapper"/>
    <!-- 2.创建数据连接池对象 -->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
          destroy-method="close">
        <property name="url" value="jdbc:mysql://192.168.204.131:3306/zkproduct?
serverTimezone=GMT" />
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="username" value="root" />
        <property name="password" value="123123" />
        <property name="maxActive" value="10" />
        <property name="minIdle" value="5" />
    </bean>
    <!-- 3.创建SqlSessionFactory，并引入数据源对象 -->
    <bean id="sqlSessionFactory"
          class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"></property>
        <property name="configLocation" value="classpath:mybatis/mybatis-config.xml"></property>
    </bean>
    <!-- 4.告诉spring容器，数据库语句代码在哪个文件中-->
    <!-- mapper.xDao接口对应resources/mapper/xDao.xml-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="mapper"></property>
    </bean>
    <!-- 5.将数据源关联到事务 -->
    <bean id="transactionManager"
          class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"></property>
    </bean>
    <!-- 6.开启事务 -->
    <tx:annotation-driven/>
</beans>

webxml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <servlet>
        <servlet-name>springMVC</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring/spring.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
        <async-supported>true</async-supported>
    </servlet>
    <servlet-mapping>
        <servlet-name>springMVC</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

OrderMapper

@Mapper
@Component
public interface OrderMapper {
    // 生成订单
    @Insert("insert into `order` (id,pid,userid) values (#{id},#{pid},#{userid})")
    int insert(Order order);
}

ProducttionMapper

@Mapper
@Component
public interface ProductMapper {
    // 查询商品（目的查库存）
    @Select("select * from product where id = #{id}")
    Product getProduct(@Param("id") int id);
    // 减库存
    @Update("update product set stock = stock-1 where id = #{id}")
    int reduceStock(@Param("id") int id);
}

ProductService

public interface ProductService {
    //减库存
    void reduceStock(int id) throws Exception;
}

ProductServiceImpl

@Service
public class ProductServiceImpl implements ProductService {

    @Autowired
    ProductMapper productMapper;
    @Autowired
    OrderMapper orderMapper;
    public void reduceStock(int id) throws Exception {
        // 获取库存（根据商品id查询商品）
        Product product = productMapper.getProduct(id);
        // 模拟网络延迟
        Thread.sleep(1000);
        if(product.getStock() <= 0)
            throw new RuntimeException("已抢光！");
        // 2.减库存
        int i = productMapper.reduceStock(id);
        if(i == 1){
            Order order = new Order();
            order.setId(UUID.randomUUID().toString());
            order.setPid(id);
            order.setUserId(101);
            orderMapper.insert(order);
        }else
            throw new RuntimeException("减库存失败，请重试！");
    }
}

controller

@Controller
public class ProductAction {

    @Autowired
    private ProductService productService;

    @GetMapping("/prodeuct/reduce")
    @ResponseBody
    public Object reduce(int id) throws Exception {
        productService.reduceStock(id);
        return "ok";
    }
}

3 启动测试

启动两次工程，端口号分别8001和8002

使用nginx做负载均衡

upstream sga{
    server 192.168.163.128:8001;
    server 192.168.163.128:8002;
}
server {
    listen 80;
    server_name localhost;
    #charset koi8-r;
    #access_log logs/host.access.log main;
    location / {
        proxy_pass http://sga;
        root html;
        index index.html index.htm;
}

使用 JMeter 模拟1秒内发出10个http请求

4. apahce提供的zookeeper客户端

基于zookeeper原生态的客户端类实现分布式是非常麻烦的，我们使用apahce提供了一个zookeeper客户端来实现

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>4.2.0</version> 
</dependency>

5. 在控制层中加入分布式锁的逻辑代码

@Controller
public class ProductAction {
    @Autowired
    private ProductService productService;
    private static String connectString =
    "192.168.204.141:2181,192.168.204.142:2181,192.168.204.143:2181";
    @GetMapping("/product/reduce")
    @ResponseBody
    public Object reduce( int id) throws Exception {
        // 重试策略 （1000毫秒试1次，最多试3次）
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);
        //1.创建curator工具对象
        CuratorFramework client =
        CuratorFrameworkFactory.newClient(connectString, retryPolicy);
        client.start();
        //2.根据工具对象创建“内部互斥锁”
        InterProcessMutex lock = new InterProcessMutex(client, "/product_"+id);
        try {
            //3.加锁
            lock.acquire();
            productService.reduceStock(id);
        }catch(Exception e){
            if(e instanceof RuntimeException){
            	throw e;
        	}
        }finally{
            //4.释放锁
            lock.release();
        }
        return "ok";
    }
}

k = new InterProcessMutex(client, “/product_”+id);
try {
//3.加锁
lock.acquire();
productService.reduceStock(id);
}catch(Exception e){
if(e instanceof RuntimeException){
throw e;
}
}finally{
//4.释放锁
lock.release();
}
return “ok”;
}
}

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阶段七模块一 分布式锁实现商品秒杀