异步数据库事务锁：电商库存扣减的防超卖秘籍
title: 异步数据库事务锁：电商库存扣减的防超卖秘籍
# 错误示例：同步方式处理库存
def reduce_stock(product_id: int, quantity: int):
product = Product.get(product_id)
if product.stock >= quantity:
product.stock -= quantity
product.save()
| 锁类型 | 实现方式 | 适用场景 | 性能影响 |
|---|---|---|---|
| 悲观锁 | SELECT FOR UPDATE | 高冲突率操作 | 较高 |
| 乐观锁 | 版本号/时间戳校验 | 低冲突率操作 | 较低 |
from tortoise.transactions import in_transaction
async def pessimistic_reduce_stock(product_id: int, quantity: int):
async with in_transaction() as conn:
# 锁定要修改的记录
product = await Product.select_for_update().using_db(conn).get(id=product_id)
if product.stock < quantity:
raise HTTPException(status_code=400, detail="库存不足")
product.stock -= quantity
await product.save(using_db=conn)
# 记录操作日志
await InventoryLog.create(
product=product,
change_amount=-quantity,
remaining=product.stock
)
from pydantic import BaseModel
class InventoryUpdate(BaseModel):
version: int # 数据版本号
quantity: int
async def optimistic_reduce_stock(product_id: int, update: InventoryUpdate):
attempt = 0
while attempt < 3: # 最大重试次数
product = await Product.get(id=product_id)
if product.stock < update.quantity:
raise HTTPException(status_code=400, detail="库存不足")
if product.version != update.version:
await asyncio.sleep(0.1 * attempt)
attempt += 1
continue
product.stock -= update.quantity
product.version += 1
updated = await Product.filter(
id=product_id,
version=update.version
).update(
stock=product.stock,
version=product.version
)
if updated:
await InventoryLog.create(
product=product,
change_amount=-update.quantity,
remaining=product.stock
)
return
raise HTTPException(status_code=409, detail="操作冲突")
Timeout waiting for lock
-- PostgreSQL调整锁超时
SET
lock_timeout = '2s';
Attempt to update stale model instance
Too many connections
# tortoise-orm配置
{
"connections": {
"default": {
"engine": "tortoise.backends.mysql",
"pool_size": 20, # 根据服务器配置调整
"connect_timeout": 3
}
}
}
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