技术整理：SpringBoot+Redis+lua脚本防止超卖

SpringBoot+redis+lua 防止超卖

一、背景

工作中遇到了有人用 RedisTemplate 的 increment去做总库存的加减，但是这种方式是保证不了原子性的还是会超卖。

redis 是可以保证原子性，但是 RedisTemplate 里面的方法去调用redis是不能保证原子性

二、优化方案

使用 lua 脚本，去执行加减操作，执行 redis 的命令，来保证原子性

三、重点代码

RedisTemplate 注入

java 复制代码

@Configuration
public class RedisConfig {

    @SuppressWarnings({"rawtypes", "unchecked"})
    @Bean(name = "redisTemplate")
    public RedisTemplate<String, Object> redisTemplate(LettuceConnectionFactory lettuceConnectionFactory) {
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(lettuceConnectionFactory);
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
        redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.afterPropertiesSet();
        return redisTemplate;
    }

抢购帮助类并支持集群模式

java 复制代码

/**
 * @Author liyue
 * @date 2024/3/22 14:31
 **/
@Component
public class SecKillProvider {

    private static final String PRODUCT_KEY = "{cluster:}productstock";
    private static final String SECKILL_SCRIPT = "lua/seckill.lua";


    @Resource
    private RedisTemplate<String, Object> redisTemplate;

    public void initStock(int stock) {
        //24小时过期
        RedisUtils.setIfAbsentTimeout(PRODUCT_KEY, stock, 86400);
    }

    //+ DateUtil.format(new Date(), DatePattern.NORM_DATE_PATTERN))
    public boolean seckill(String userId) {
        //调用lua脚本并执行
        DefaultRedisScript<Long> redisScript = new DefaultRedisScript<>();
        redisScript.setResultType(Long.class);//返回类型是Long
        //lua文件存放在resources目录下的redis文件夹内
        redisScript.setScriptSource(new ResourceScriptSource(new ClassPathResource(SECKILL_SCRIPT)));

        Integer result = (Integer) redisTemplate.opsForValue().get(PRODUCT_KEY);


        System.out.println(result);
        System.out.println(PRODUCT_KEY);
        Long stock = redisTemplate.execute(redisScript, Arrays.asList(PRODUCT_KEY));

        System.out.println("执行完成--=--stock=" + stock);

        if (stock >= 0) {
            // 抢购成功，可以继续处理订单等逻辑
            System.out.println("User " + userId + " seckill success!");
            return true;
        } else {
            // 抢购失败，库存不足
            System.out.println("User " + userId + " seckill failed!");
            return false;
        }
    }
}

lua 脚本

java 复制代码

local stock = tonumber(redis.call('get', KEYS[1]))
if stock and stock > 0 then
    redis.call('decr', KEYS[1])
    return stock - 1
else
    return -1
end

并发测试类

java 复制代码

/**
 * @Author liyue
 * @date 2024/3/22 15:14
 **/
@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j
public class SecKillProviderTest {

    @Resource
    private SecKillProvider secKillProvider;


    @Test
    public void t() throws InterruptedException {

        secKillProvider.initStock(10);

        for (int i = 0; i < 2000; i++) {
            new Thread(new Mythread(i)).start();
        }

        Thread.sleep(10000);

    }

    class Mythread implements Runnable {

        private int num;

        Mythread(int num) {
            this.num = num;
        }

        @SuppressWarnings("unchecked")
       SecKillProvider secKillProvider = SpringUtil.getBean("secKillProvider");

        @Override
        public void run() {
            secKillProvider.seckill(String.valueOf(num));
        }
    }
}

总结

使用这种方式，读取文件可以优化成sha的方式去去读取。后面再进行调整，测试类可以模拟并发情况。测试没有什么问题。

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