优惠券秒杀案例 - CAS、Redis+Lua脚本解决高并发并行

public Result seckillVoucher(Long voucherId) {
 
        SeckillVoucher voucher = iSeckillVoucherService.getById(voucherId);
        if (voucher.getBeginTime().isAfter(LocalDateTime.now())) {
            return Result.fail("活动还未开始");
        }
        if (voucher.getEndTime().isBefore(LocalDateTime.now())) {
            return Result.fail("活动已经结束");
        }
        // 库存不足
        if(voucher.getStock() < 1){
            return Result.fail("库存不足");
        }
        // 注意两点
        // 1.释放锁时机 先提交事务，在释放锁
        // 2.防止事务失效
        Long userHolder = UserHolder.getUser().getId();
        synchronized (userHolder.toString().intern()){
            // 使用代理对象调用该函数，防止事务失效
            IVoucherOrderService proxy = (IVoucherOrderService) AopContext.currentProxy();
            return proxy.createOrder(voucherId);
        }
 
 
    }
 
    @Transactional
    public Result createOrder(Long voucherId){
        // 一人一单
        Long userHolder = UserHolder.getUser().getId();
        int count = query().eq("user_id", userHolder).eq("voucher_id", voucherId).count();
        if(count > 0){
            return Result.fail("用户已经购买一次");
        }
        // 更新库存
        boolean success = iSeckillVoucherService.update()
                .setSql("stock = stock - 1")
                .eq("voucher_id", voucherId)
                .gt("stock", 0).update();
        if(!success){
            return Result.fail("库存不足");
        }
        // 添加下单数据
        VoucherOrder voucherOrder = new VoucherOrder();
        // 全局ID
        long nextId = redisIdWorker.nextId("order");
        voucherOrder.setId(nextId);
        // voucher_id
        voucherOrder.setVoucherId(voucherId);
        // 用户id
        voucherOrder.setUserId(UserHolder.getUser().getId());
        // 存数据
        save(voucherOrder);
        // 返回订单id
        return Result.ok(nextId);
    }

setnx lock thread1 # 普通
# Redis可能宕机
expire lock 10 # 设置过期时间作为保底策略

set lock thread1 EX 10 NX

del lock # 手动释放锁

public class SimpleRedisTemplate {
 
    private String name;
    private StringRedisTemplate stringRedisTemplate;
    private static final String KEY_PREFIX = "lock:";
    private static final String ID_PREFIX = UUID.randomUUID().toString(true) + "-";
 
    public SimpleRedisTemplate(String name, StringRedisTemplate stringRedisTemplate) {
        this.name = name;
        this.stringRedisTemplate = stringRedisTemplate;
    }
 
    /**
     * 获取锁
     * @param timeoutSec
     * @return
     */
    public boolean tryLock(Long timeoutSec){
        // 1.利用UUID区分不同服务的相同线程，拼接上线程ID
        String threadId = ID_PREFIX + Thread.currentThread().getId();
        Boolean b = stringRedisTemplate
                .opsForValue()
                .setIfAbsent(name + KEY_PREFIX, threadId , timeoutSec, TimeUnit.MINUTES);
        return Boolean.TRUE.equals(b); // 防止b为null
    }
 
    /**
     * 释放锁
     */
    public void unLock(){
        // 获取锁 是自己的才释放
        String lockId = stringRedisTemplate.opsForValue().get(name + KEY_PREFIX);
        String threadId = ID_PREFIX + Thread.currentThread().getId();
        if(threadId.equals(lockId)){
            stringRedisTemplate.delete(name + KEY_PREFIX);
        }
 
    }
 
}

-- 判断线程标识与锁标识是否一致
if(AVGV[1] == redis.call("get", KEYS[1])) then
  // 释放锁
  return redis.call("del", KEYS[1]);
end
return 0;

    private static final DefaultRedisScript<Long> UNLOCK_SCRIPT;
    // 提前加载Lua脚本
    static {
        UNLOCK_SCRIPT = new DefaultRedisScript<>();
        UNLOCK_SCRIPT.setLocation(new ClassPathResource("unlock.lua"));
        UNLOCK_SCRIPT.setResultType(Long.class);
    }
    public void unLock(){
        // 调用Lua脚本
        stringRedisTemplate.execute(
                UNLOCK_SCRIPT,
                Collections.singletonList(name + KEY_PREFIX),
                ID_PREFIX + Thread.currentThread().getId());
    }