Example code of second kill based on MySQL optimistic lock

Catalog

explain

Concrete realization

Code implementation

explain

If your project traffic is very small , Don't worry about concurrent purchase requests at all , So it doesn't make much sense to do such a system . But if your system is like 12306 like that , Accept the test of high concurrent visits and orders , Then you need a complete set of process protection measures , To ensure that your system will not be hung up during peak user traffic .

Advanced redis+mq Realization ： Reference resources springboot + rabbitmq + redis Achieve second kill

Strictly prevent oversold
Ensure the user experience ： High and low , Don't open the web page , Payment failed , The shopping cart can't get in , The address can't be changed
Prevent black production ： Prevent malicious people from pocketing all the benefits you should have distributed to the masses through various technical means

Concrete realization

1、 The core
mysql Optimistic lock prevents oversold

Optimistic lock refers to the operation of the database ( update operation ), The idea is optimistic , Think this operation will not lead to conflict , When operating data , Without any other special treatment （ That is, no lock ）, And after the update , To judge whether there is a conflict .

Here is the reference. Usually, the implementation is like this ： When the data in the table is operated ( to update ), First, add a version to the data table (version) Field , Every time you operate , Add the version number of that record to 1. That is to find out the record first , Take out version Field , If you want to operate on that record ( to update ), Then judge the moment first version Whether the value of is the same as the value of version The values are equal , If equal , It means that during this period , There is no other program to operate it , Then you can perform the update , take version Add... To the value of the field 1; If you find out when you update version Value and just get out of version The values of , It means that there are other procedures to operate it during this period , Do not update .

2、 Create table statement
stock Commodity list

-- ------------------------------ Table structure for stock-- ----------------------------DROP TABLE IF EXISTS `stock`;CREATE TABLE `stock` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(50) NOT NULL DEFAULT '' COMMENT ' name ', `count` int(11) NOT NULL COMMENT ' stock ', `sale` int(11) NOT NULL COMMENT ' sold ', `version` int(11) NOT NULL COMMENT ' Optimism lock , Version number ', PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Initialization data ：

stock_order The order sheet

-- ------------------------------ Table structure for stock_order-- ----------------------------DROP TABLE IF EXISTS `stock_order`;CREATE TABLE `stock_order` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `sid` int(11) NOT NULL COMMENT ' stock ID', `name` varchar(30) NOT NULL DEFAULT '' COMMENT ' Name of commodity ', `create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT ' Creation time ', PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8;

3、 The business process

Code implementation

1、pom

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <!--mysql--> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>1.3.0</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency> <!--druid--> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.1.10</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid-spring-boot-starter</artifactId> <version>1.1.10</version> </dependency> <dependency> <groupId>com.github.pagehelper</groupId> <artifactId>pagehelper</artifactId> <version>5.2.0</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.8</version> </dependency> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter</artifactId> <version>5.8.2</version> <scope>test</scope> </dependency>

2、model

It can be configured through reverse engineering , Reference resources idea+mybatis Reverse engineering

4、dao

public interface StockMapper { Stock checkStock(Integer id);// Verify inventory int updateSale(Stock stock);// Deducting inventory }public interface StockOrderMapper { // Create order void createOrder(StockOrder order);}

5、sql

Commodity verification and inventory reduction

<select id="checkStock" parameterType="java.lang.Integer" resultType="com.yy.msserver.model.vo.Stock"> select * from stock where id = #{id} </select> <update id="updateSale" parameterType="com.yy.msserver.model.vo.Stock" > update stock set sale = #{sale,jdbcType=INTEGER} + 1, version = #{version,jdbcType=INTEGER} + 1, count = #{count,jdbcType=INTEGER} - 1 where id = #{id,jdbcType=INTEGER} AND count > 0 AND version = #{version} </update>

Place the order

<insert id="createOrder" parameterType="com.yy.msserver.model.vo.StockOrder"> insert into stock_order (sid, name, create_time) values (#{sid,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, #{createTime,jdbcType=TIMESTAMP}) </insert>

6、service

public interface StockOrderService { public Integer createOrder(Integer id);}

7、 Realization

/** * @author code * @Date 2022/6/24 9:25 * Description Order fulfillment * Version 1.0 */@Servicepublic class StockOrderServiceImpl implements StockOrderService { @Autowired private StockOrderMapper stockOrderMapper; @Autowired private StockMapper stockMapper; @Override @Transactional(rollbackFor = Exception.class) public Integer createOrder(Integer id) { // Verify inventory Stock stock = checkStock(id); if(stock.getCount()>0){ System.out.println(" Current stock ：" + stock.getCount()); // Inventory deduction if(updateSale(stock) == 1){ return createOrder(stock); }else { return 0; } } return 0; } // Verify inventory private Stock checkStock(Integer id) { return stockMapper.checkStock(id); } // Inventory deduction private int updateSale(Stock stock){ return stockMapper.updateSale(stock); } // Place the order private Integer createOrder(Stock stock){ StockOrder order = new StockOrder(); order.setSid(stock.getId()); order.setCreateTime(new Date()); order.setName(stock.getName()); stockOrderMapper.createOrder(order); return order.getId(); }}

8、 test
simulation 100 Participation and activities

@SpringBootTestclass MsServerApplicationTests { @Autowired private StockOrderService stockOrderService; @Test void contextLoads() throws InterruptedException { // Inventory initialization is 10, Through here CountDownLatch And thread pool emulation 100 concurrent int threadTotal = 100; ExecutorService executorService = Executors.newCachedThreadPool(); final CountDownLatch countDownLatch = new CountDownLatch(threadTotal); for (int i = 0; i < threadTotal ; i++) { int uid = i; executorService.execute(() -> { try { stockOrderService.createOrder(1); } catch (Exception e) { e.printStackTrace(); } countDownLatch.countDown(); }); } countDownLatch.await(); executorService.shutdown(); }}

9、 result

Commodity list

The order sheet

This article is based on mysql This is the article about the example code of optimistic lock to realize seckill , More about mysql Please search the previous articles of software development network or continue to browse the relevant articles below. I hope you will support software development network more in the future ！