当前位置:网站首页>Jd.com 2: how to prevent oversold in the deduction process of commodity inventory?
Jd.com 2: how to prevent oversold in the deduction process of commodity inventory?
2022-07-06 04:17:00 【End code life】
In the process of commodity purchase , Inventory deduction process , The general operation is as follows :
- select According to the goods id Query the inventory of goods .
- According to the number of orders , Calculate whether the inventory is sufficient , If the inventory is insufficient, an exception of insufficient inventory will be thrown , If there is enough stock , Then subtract the deducted inventory to get the latest inventory residual value .
- set Set the latest inventory remaining value .
The pseudo code of the above process is as follows :
// According to the goods id Get the remaining inventory of goods
select stock_remaing from stock_table where id=${goodsId};
// Operating inventory
// Compare inventory
if(stock_remaing <quantity){
// Throw the exception of insufficient inventory
}
else{
// Inventory value after deduction
int new_stock=stock_remaing - quantity;
}
// According to the goods id Set the calculated inventory
update stock_table set stock_remaing =${new_stock} id=${goodsId};
- 1.
- 2.
- 3.
- 4.
- 5.
- 6.
- 7.
- 8.
- 9.
- 10.
- 11.
- 12.
- 13.
- 14.
- 15.
1、 Concurrent modification of database storage oversold
If the isolation level of database transactions is not serialization (serializable), According to the characteristics of transactions , During concurrent modification , Write overwrite may occur .
hypothesis , Remaining inventory of goods stock_remaing by 100, Customer A Place an order 20, Customer B Place an order 30, When deducting inventory concurrently , There may be oversold . If the customer A And the customer B At the same time, the remaining inventory is 100, The value submitted after the transaction will overwrite the value submitted by the previous customer , It is possible that the remaining inventory is 80 perhaps 70. The process is as follows :
2、 Lock update Repository
In order to control transactions , Prevent write overwrite , You'll think of using select for update The way , Lock the inventory of this commodity , Then do the rest .
The process is as follows :
above , Use pessimistic locking , In distributed services , If concurrency is high , Stock deduction is a serial operation , Efficiency is very low .
3、 Update with optimistic lock
At the time of the update , Use (CAS+ Version number update )+ Retry conditions ( Number of retries or retry time limit ) Update inventory in an optimistic way . here , If , Customer A And the customer B At the same time, the remaining inventory is read 100, At the time of the update , One operation will fail . The process is as follows :
This method can greatly improve the concurrency , It can also ensure the consistency of data ; It is controlled by the conditions of retry times and retry time , It can prevent the database pressure caused by too many retries .
4、 Can it be executed by direct decrement ?
When deducting inventory , Some people propose not to implement select, Calculation ,set Three stage operation , The way of direct deduction , And make a judgment when the deduction is less than zero . The pseudocode is as follows :
update stock_table set remaing_stock=remaing_stock-${quantity}
where id = goods id
and remaing_stock>${quantity};
- 1.
- 2.
- 3.
In a distributed service call , Because the network is abnormal , Get server exception , Maybe when the microservice is invoked , There is a service retry . for example , Gateway timeout for scenario , Service retry mechanism . here , This method does not satisfy idempotency , And there are many deductions . for example , When the same user deducts inventory , Service retry , In extreme cases , The user has performed inventory deduction for multiple times , Then there is oversold .
5、 have access to redis Do you want to deduct inventory ?
Because I haven't studied redis Source code , For this way, I refer to Daniel's reply , The answer is that you can use redis Transaction deduction balance of , But in CAS Mechanism ratio mysql No advantage , High performance is due to its memory storage , The side effect is the risk of data loss .
PS: Prevent missing this article , You can like it , It's easy to browse and search .
边栏推荐
- 解决“C2001:常量中有换行符“编译问题
- View 工作流程
- P3500 [poi2010]tes intelligence test (two points & offline)
- Ipv4中的A 、B、C类网络及子网掩码
- Basic knowledge of binary tree, BFC, DFS
- Data processing methods - smote series and adasyn
- Global and Chinese market of rubber wheel wedges 2022-2028: Research Report on technology, participants, trends, market size and share
- How can programmers resist the "three poisons" of "greed, anger and ignorance"?
- HotSpot VM
- 综合能力测评系统
猜你喜欢
Solutions: word coverage restoration, longest serial number, Xiaoyu buys stationery, Xiaoyu's electricity bill
When debugging after pycharm remote server is connected, trying to add breakpoint to file that does not exist: /data appears_ sda/d:/segmentation
10個 Istio 流量管理 最常用的例子,你知道幾個?
[Zhao Yuqiang] deploy kubernetes cluster with binary package
Fundamentals of SQL database operation
Certbot failed to update certificate solution
JVM garbage collector concept
[Key shake elimination] development of key shake elimination module based on FPGA
MySql數據庫root賬戶無法遠程登陸解决辦法
Detailed explanation of serialization and deserialization
随机推荐
View 工作流程
POI add border
P3033 [usaco11nov]cow steelchase g (similar to minimum path coverage)
2/13 qaq~~ greed + binary prefix sum + number theory (find the greatest common factor of multiple numbers)
Basic use of MySQL (it is recommended to read and recite the content)
User datagram protocol UDP
How does technology have the ability to solve problems perfectly
MySQL master-slave replication
C. The Third Problem(找规律)
Solution to the problem that the root account of MySQL database cannot be logged in remotely
Yyds dry goods inventory web components series (VII) -- life cycle of custom components
Mlapi series - 04 - network variables and network serialization [network synchronization]
Certbot failed to update certificate solution
Python book learning notes - Chapter 09 section 01 create and use classes
JVM garbage collector concept
HotSpot VM
About some basic DP -- those things about coins (the basic introduction of DP)
One question per day (Mathematics)
Web components series (VII) -- life cycle of custom components
Stack and queue