How to Prevent Duplicate Orders: Strategies and Workflows
Table of Contents
- Introduction
- User Workflow for Placing an Order
- Technical Strategies to Prevent Duplicate Orders
- Workflow Diagram
Introduction
Preventing duplicate orders is crucial in e-commerce platforms and other systems where a user can place an order.
User Workflow for Placing an Order
The initial phase of order placement includes:
- Browsing Products: Users browse through products and view details.
- Add to Cart or Checkout: Users either add items to their shopping cart or proceed directly to checkout.
- Confirm and Submit Order: After checkout, users are taken to an order confirmation page. Upon submitting, a unique order ID is generated.
Technical Strategies to Prevent Duplicate Orders
Duplicate orders usually occur due to:
- Users resubmitting or double-clicking the submit button.
- Network glitches causing retries.
Understanding Idempotency and Deduplication
- Idempotency: Multiple identical requests yield the same result.
- Deduplication: Prevents multiple identical requests from being processed.
Implementation Strategies
Database Level Idempotency
You can add a requestId field in the order table and set it as a unique index.
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PlaceOrderResVO placeOrder(PlaceOrderReqVO reqVO) {
try {
// Place order logic
// Generate order ID
String oid = generateOid();
// Insert into DB
Order order = orderMapper.saveOrder(orderDO);
resVO.setOid(order.getOid());
return resVO;
} catch (UniqueKeyViolationException e) {
// Duplicate request exception caught
Order order = getOrderByRequestId(reqVO.getRequestId());
resVO.setOid(order.getOid());
return resVO;
}
}
Redis for Deduplication
Use Redis distributed locks to prevent concurrent duplicate requests.
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PlaceOrderResVO placeOrder(PlaceOrderReqVO reqVO) {
RLock orderLock = redissonClient.getLock("ORDER_LOCK_" + reqVO.getRequestId());
if (orderLock.isLocked()) {
throw new OrderRepeatException();
}
orderLock.lock();
try {
// Check if the order exists in Redis
if (redissonClient.getBucket("ORDER_" + reqVO.getRequestId()).isExists()) {
return redissonClient.getBucket("ORDER_" + reqVO.getRequestId()).get();
}
// Place order logic
// Insert into DB
Order order = orderMapper.saveOrder(orderDO);
// Cache result in Redis
redissonClient.getBucket("ORDER_" + reqVO.getRequestId()).set(order);
return resVO;
} finally {
orderLock.unlock();
}
}
Workflow Diagram
Here’s a simplified workflow diagram that includes both the user’s actions and the subsequent system operations:
This wraps up our article. Understanding the user workflow and implementing robust server-side strategies can help in preventing duplicate orders effectively.
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