express-idempotency

import express from 'express'; import { idempotency, IIdempotencyDataAdapter } from 'express-idempotency'; import { v4 as uuidv4 } from 'uuid'; // IMPORTANT: For production, replace this with a persistent storage solution (Redis, MongoDB, etc.) // The default in-memory adapter is not suitable for production environments. class InMemoryDataAdapter implements IIdempotencyDataAdapter { private store = new Map<string, { request: any; response: any; status: string }>(); async get(idempotencyKey: string): Promise<{ request: any; response: any; status: string } | null> { return this.store.get(idempotencyKey) || null; } async set(idempotencyKey: string, request: any, response: any, status: string): Promise<void> { this.store.set(idempotencyKey, { request, response, status }); } async remove(idempotencyKey: string): Promise<void> { this.store.delete(idempotencyKey); } } const app = express(); const port = 3000; // Middleware to parse JSON bodies app.use(express.json()); // Initialize the idempotency middleware. Always provide a production-ready data adapter. app.use( idempotency({ dataAdapter: new InMemoryDataAdapter(), // Replace with a real data adapter for production! // Other options like idempotencyKeyHeader, intentValidator, responseValidator can be customized here. }) ); // Declare `getSharedIdempotencyService` for TypeScript if it's globally available. // In a real application, consider explicitly importing a service factory if available, // or accessing a request-scoped service if the middleware attaches it (e.g., `req.idempotencyService`). declare function getSharedIdempotencyService(): { isHit(req: express.Request): boolean; reportError(req: express.Request): void; }; app.post('/process-payment', (req, res) => { // Retrieve the IdempotencyService instance. const idempotencyService = getSharedIdempotencyService(); // Crucial: Check if the request is an idempotency hit. If so, prevent further processing. if (idempotencyService.isHit(req)) { console.log('Idempotency hit detected, a cached response should have been sent by the middleware.'); // The middleware is designed to send the cached response and then call next(). // Your route handler should return early here to avoid re-executing business logic. return; } // --- Your business logic starts here (only for non-idempotent requests) --- console.log('Processing new payment for:', req.body); const transactionId = uuidv4(); const amount = req.body.amount; if (amount <= 0) { // If an error occurs during processing, report it to the middleware // so that the idempotency state for this key can be cleared or updated. idempotencyService.reportError(req); return res.status(400).json({ error: 'Amount must be positive.' }); } // Simulate an asynchronous payment processing operation setTimeout(() => { const responseData = { message: `Payment for ${amount} processed successfully.`, transactionId: transactionId, status: 'completed', }; res.status(200).json(responseData); console.log('Payment processed and response sent.'); }, 1000); }); app.listen(port, () => { console.log(`Server listening at http://localhost:${port}`); console.log(` To test, send a POST request with an 'Idempotency-Key' header:`) console.log(`curl -X POST -H "Content-Type: application/json" -H "Idempotency-Key: my-unique-key-123" -d '{"amount": 100}' http://localhost:${port}/process-payment`); console.log(` Repeat the curl command with the *same* 'my-unique-key-123' to observe idempotency in action (cached response).`); console.log(`Use a *different* key for a new payment.`); });