Talk about the design and implementation logic of payment process

Novices are afraid of the business that veterans have a headache ;

One 、 Business background

Usually in the business system , Will more or less involve payment related functions ; For some inexperienced students , The most important thing is to face the logic of this kind of payment and settlement , Because of any details in the process , May cause reconciliation exceptions ;

After the error occurs , Then I want to repair the process , The time cost is high , It also involves the leveling of wrong data , Eventually, it is likely to lead to disorderly accounts and unclear results , Then manual intervention is needed ;

In the payment scenario , It not only involves many complex businesses , Settlement rules , Long process , Third party docking , Among them, many technical details are involved , such as ： Business management 、 Asynchronous processing 、 Retry mechanism 、 Lock, etc ; Let's analyze the specific detail logic .

Two 、 Payment business

1、 Process disassembly

When facing complex business , The most basic ability is to understand the process into modules , Manage each module , Then consider how to connect the whole process , So as to form ideas and experience to solve problems ;

The figure below is a common decomposition of trading scenarios , It can be roughly divided into four modules ：

• Book management ： For users who have opened the payment function , Must have clear management information ; For example, available , frozen , Bills, etc ;
• Transaction flow ： The running records of the whole fund management , Not limited to trading scenarios , And recharge , Withdrawal , Refund, etc ;
• Payment docking ： Usually, the payment function in the process is realized by connecting with the third-party payment platform , So make a good record of requests and messages ;
• Order structure ： For example, in e-commerce transactions , Order model management , Split order strategy, etc , Specifications of goods paid, etc ;

Here is just an analysis from a conventional transaction process , The actual detailed description will be much more complicated than the legend , Although the business details vary , But the treatment ideas are generally the same ; Then design the flow sequence diagram according to each module , Plan the connection and cooperation between nodes ;

2、 Process sequence

Through the design of sequence diagram , To analyze how each node should handle when connecting and cooperating , In payment business , It is usually divided into before payment 、 Payment docking 、 There are three core stages after payment ：

• Before payment ： When placing an order , Build order model , Check the inventory according to the splitting rules 、 Commodity status, etc , Then freeze the account funds , Generate transaction flow , At this time, the status is to be paid ;
• Payment docking ： After the business model is initialized successfully before payment , Build a third-party payment docking request , Initiate payment process , And record the corresponding request actions and parameters , Waiting for notification of payment results ;
• After payment ： According to the success of the payment results , Perform the corresponding business model status update , If the payment is successful, the transaction is recorded 、 Frozen funds 、 Order structure and inventory need to be updated ;

In fact, after having a clear understanding of the business and splitting , Then do a good job in the design of timing process , This has made a complex scene look much simpler , Then it is to design the data structure of each node ;

3、 The structure design

Based on the above business scenario analysis and disassembly , And the presentation of process sequence diagram , It is easy to output a structural design of basic dimensions , The following figure can be used as a reference ：

• Book management ： Three core dimensions , Amount of account , Available balance , Freezing amount ;
• Transaction records ： Store users' transaction actions , However, multiple transaction details may be generated , A typical scenario is to place an order in a shopping cart ;
• Transaction details ： Usually because the order is split , As a result, the transaction is split into multiple details , And then pay the funds to different businesses ;
• Payment docking ： When requesting a third-party payment platform , Need to record request parameters , And the message of the third party callback notification ;
• Order records ： There may be multiple split sub orders in an order , There are also many splitting strategies , Like the warehouse , merchants , Category, etc ;
• The order details ： Manage the information of each sub order , Goods ordered 、 specifications 、 round turn 、 The unit price 、 Number 、 Amount, etc. ;

Even if you just look at the simple design above , Can feel the complexity of payment business , What's more, it will be superimposed after preferential rules such as red envelopes or full discounts , Its complexity can be imagined ;

Of course, if there is a clear development specification , In complex versions , All development must output business decomposition ideas , Timing and structure design , Code after unified Review , In this way, even complex businesses will have great quality assurance .

3、 ... and 、 Related business

The above list analyzes the process from the main logic of payment , In fact, the business involved is far more than those mentioned in the process , Take common e-commerce scenarios as an example , There is also commodity management in the transaction 、 Inventory management 、 Physical distribution management , Payment docking will also involve preferential rule embedding and so on ;

Commodity management

• Commodity subject ： Maintain the information of each dimension of goods , And provide various specifications and options , And the basic pricing ladder , Build product details ;
• Warehouse management ： After the order is split , You need to verify the storage information according to the commodity number , Carry out corresponding inventory freezing and warehouse delivery after payment ;

Coupon rules

• Coupon subject ： In order to adapt to more business scenarios , There need to be many designs for preferential rules , Such as full reduction or discount ratio 、 Price ladder discount 、 Validity limit, etc ;
• Distribution rules ： Support daily operational activities , Maintenance of user life cycle , And the transformation of channel flow , Provide the basic ability of user group marketing ;

Here is a brief description of the commodity and coupon business , Are closely related to the payment process , For example, the inventory is insufficient after splitting , This item needs to be removed ; The use strategy of coupons in payment , And how to handle the refund ;

Four 、 practice

Finally, from the perspective of technical implementation , Summarize some key issues in the payment process ：

• business model ： Have a clear understanding of the business , And can split the core nodes , Design the corresponding process sequence and data structure ;
• Business management ： Commonly used in the transaction process TCC Transaction mechanism , namely Try( Preprocessing )、Confirm( confirm )、Cancel( Cancel ) Pattern ;
• Lock and retry ： Send the message of successful payment after payment , Then update the business , It is usually necessary to lock the processed order number , Avoid data problems caused by message retry mechanism ;
• Capital settlement ： Calculation of amount involved , The problem of accuracy loss cannot occur naturally , In a transaction, it must be ensured that each fund can be verified by reconciliation ;
• Process maintenance ： The process itself is difficult to ensure that there are no errors , It needs to be developed , Provide a visual interface of the process , And support the mechanism of manual maintenance ;

Many complex business scenario management , Both need a long-term iterative process , But the premise needs to firmly grasp the core logic ; Understanding business is a process from complexity to simplicity , The realization of business is a process from shallow to deep , Analysis and understanding , To the ground , Then to exploration and innovation .

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