Redis+MQ高并发秒杀的技术方案与实现

-- 启用Redis命令复制，确保脚本在集群环境中正确同步
redis.replicate_commands()
 
-- 1. 防重提交校验：通过用户ID+Token判断是否重复提交
-- KEYS[2]为用户ID（uid），ARGV[2]为本次请求的Token
if redis.call('hexists', KEYS[2], ARGV[2]) == 1 then
    return redis.error_reply('repeat submit')  -- 重复提交，返回错误
end 
 
-- 2. 库存充足性校验
local product_id = KEYS[1]  -- 商品ID
local stock = redis.call('get', KEYS[1])  -- 获取当前库存
if not stock then  -- 库存不存在（如商品未上架）
    return redis.error_reply('product not found')
end
if tonumber(stock) < tonumber(ARGV[1]) then  -- 库存不足
    return redis.error_reply('stock is not enough')
end 
 
-- 3. 执行库存扣减
local remaining_stock = tonumber(stock) - tonumber(ARGV[1])
redis.call('set', KEYS[1], tostring(remaining_stock))  -- 更新库存
 
-- 4. 记录交易流水（用于后续一致性校验）
local time = redis.call('time')  -- 获取当前时间（秒+微秒）
local currentTimeMillis = (time[1] * 1000) + math.floor(time[2] / 1000)  -- 转换为毫秒时间戳
-- 存储流水到Hash结构：用户ID → Token → 流水详情
redis.call('hset', KEYS[2], ARGV[2], 
    cjson.encode({
        action = '扣减库存',
        product = product_id,
        from = stock,  -- 扣减前库存
        to = remaining_stock,  -- 扣减后库存
        change = ARGV[1],  -- 扣减数量
        token = ARGV[2],
        timestamp = currentTimeMillis
    })
)
 
return remaining_stock  -- 返回扣减后库存

@Service
public class SeckillService {
 
    @Autowired
    private StringRedisTemplate redisTemplate;
 
    // 加载Lua脚本
    private DefaultRedisScript<Long> stockScript;
 
    @PostConstruct
    public void init() {
        stockScript = new DefaultRedisScript<>();
        stockScript.setScriptSource(new ResourceScriptSource(new ClassPathResource("seckill.lua")));
        stockScript.setResultType(Long.class);
    }
 
    /**
     * 执行Redis库存预扣减
     * @param productId 商品ID
     * @param uid 用户ID
     * @param quantity 购买数量
     * @param token 防重Token
     * @return 扣减后库存（-1表示失败）
     */
    public Long preDeductStock(String productId, String uid, Integer quantity, String token) {
        try {
            // 执行Lua脚本：KEYS = [商品ID, 用户ID]，ARGV = [数量, Token]
            return redisTemplate.execute(
                stockScript,
                Arrays.asList(productId, uid),
                quantity.toString(),
                token
            );
        } catch (Exception e) {
            log.error("Redis预扣减失败", e);
            return -1L;
        }
    }
}

// 发送半消息
public void sendHalfMessage(String productId, String uid, String token, Integer quantity) {
    // 构建消息
    Message message = new Message(
        "seckill_topic",  // 主题
        "stock_deduct",   // 标签
        JSON.toJSONString(new SeckillMessage(productId, uid, token, quantity)).getBytes()
    );
    // 发送事务消息
    TransactionSendResult result = rocketMQTemplate.sendMessageInTransaction(
        "seckill_producer_group",  // 生产者组
        message,
        null  // 本地事务参数（可传递上下文）
    );
    log.info("半消息发送结果：{}", result.getSendStatus());
}

@Component
public class SeckillTransactionListener implements TransactionListener {
 
    @Autowired
    private StringRedisTemplate redisTemplate;
 
    // 执行本地事务
    @Override
    public LocalTransactionState executeLocalTransaction(Message msg, Object arg) {
        try {
            SeckillMessage message = JSON.parseObject(new String(msg.getBody()), SeckillMessage.class);
            // 检查Redis中是否存在对应流水（验证预扣减成功）
            Boolean flag = redisTemplate.opsForHash().hasKey(
                message.getUid(),  // Hash key：用户ID
                message.getToken()  // Hash field：Token
            );
            return flag ? RocketMQLocalTransactionState.COMMIT : RocketMQLocalTransactionState.ROLLBACK;
        } catch (Exception e) {
            return RocketMQLocalTransactionState.UNKNOWN;  // 未知状态，触发回查
        }
    }
 
    // 消息回查（解决超时未确认问题）
    @Override
    public LocalTransactionState checkLocalTransaction(MessageExt msg) {
        SeckillMessage message = JSON.parseObject(new String(msg.getBody()), SeckillMessage.class);
        // 回查逻辑：再次检查流水是否存在
        Boolean flag = redisTemplate.opsForHash().hasKey(message.getUid(), message.getToken());
        return flag ? RocketMQLocalTransactionState.COMMIT : RocketMQLocalTransactionState.ROLLBACK;
    }
}

@Component
@RocketMQMessageListener(
    topic = "seckill_topic",
    consumerGroup = "seckill_consumer_group",
    messageModel = MessageModel.CLUSTERING
)
public class SeckillConsumer implements RocketMQListener<MessageExt> {
 
    @Autowired
    private JdbcTemplate jdbcTemplate;
 
    @Override
    public void onMessage(MessageExt message) {
        SeckillMessage msg = JSON.parseObject(new String(message.getBody()), SeckillMessage.class);
        String productId = msg.getProductId();
        int quantity = msg.getQuantity();
 
        // 数据库扣减（使用乐观锁防超卖）
        String sql = "UPDATE product_stock " +
                    "SET stock = stock - ?, version = version + 1 " +
                    "WHERE product_id = ? AND stock >= ? AND version = ?";
 
        // 1. 查询当前版本号
        Integer version = jdbcTemplate.queryForObject(
            "SELECT version FROM product_stock WHERE product_id = ?",
            Integer.class,
            productId
        );
 
        // 2. 执行扣减（乐观锁保证原子性）
        int rows = jdbcTemplate.update(sql, quantity, productId, quantity, version);
        if (rows > 0) {
            // 扣减成功：记录数据库流水
            jdbcTemplate.update(
                "INSERT INTO stock_flow (product_id, quantity, op_type, create_time) " +
                "VALUES (?, ?, 'SECKILL', NOW())",
                productId, quantity
            );
            // 确认消费成功（返回ACK）
        } else {
            // 扣减失败：触发重试（MQ默认重试机制）
            throw new RuntimeException("数据库扣减失败，触发重试");
        }
    }
}

@Scheduled(cron = "0 0 */1 * * ?")  // 每小时执行一次
public void reconcileStock() {
    // 1. 扫描Redis中未同步到MySQL的流水
    Set<String> uids = redisTemplate.keys("uid:*");  // 假设用户ID前缀为uid:
    for (String uid : uids) {
        Map<Object, Object> tokenMap = redisTemplate.opsForHash().entries(uid);
        for (Map.Entry<Object, Object> entry : tokenMap.entrySet()) {
            String token = (String) entry.getKey();
            String flowJson = (String) entry.getValue();
            SeckillFlow flow = JSON.parseObject(flowJson, SeckillFlow.class);
 
            // 2. 检查MySQL是否有对应订单
            Integer count = jdbcTemplate.queryForObject(
                "SELECT COUNT(1) FROM orders WHERE product_id = ? AND uid = ? AND token = ?",
                Integer.class,
                flow.getProduct(), flow.getUid(), token
            );
 
            if (count == 0) {
                // 3. 未找到订单 → 人工介入或自动回滚Redis库存
                log.warn("发现不一致：Redis有流水但MySQL无订单，product={}, uid={}", flow.getProduct(), uid);
                // redisTemplate.opsForValue().increment(flow.getProduct(), Integer.parseInt(flow.getChange()));
            }
        }
    }
}