👀 Views: 55 💬 Answers: 1 📅 Created: 2025-06-12

node.js redis express clustering JavaScript

I'm a bit lost with I'm using Node.js v18 with the `cluster` module to implement a simple web server that handles user sessions stored in Redis. However, I'm experiencing data inconsistency issues when multiple worker processes try to read and write to the same Redis keys simultaneously. For instance, when I set a session key in one worker, other workers sometimes read stale or empty data. I've tried to implement a locking mechanism using the `SETNX` command in Redis, but it seems like the operations are still conflicting. Here's a simplified version of my code: ```javascript const cluster = require('cluster'); const express = require('express'); const redis = require('redis'); const { promisify } = require('util'); if (cluster.isMaster) { const numCPUs = require('os').cpus().length; for (let i = 0; i < numCPUs; i++) { cluster.fork(); } } else { const app = express(); const client = redis.createClient(); const getAsync = promisify(client.get).bind(client); const setAsync = promisify(client.set).bind(client); app.get('/session/:id', async (req, res) => { const sessionId = req.params.id; const sessionData = await getAsync(sessionId); res.send(sessionData || 'No session found'); }); app.post('/session/:id', async (req, res) => { const sessionId = req.params.id; const sessionData = JSON.stringify(req.body); await setAsync(sessionId, sessionData); res.send('Session saved'); }); app.listen(3000, () => { console.log(`Worker ${process.pid} started`); }); } ``` When I try to create and retrieve session data concurrently, I find that sometimes one worker overwrites the session data written by another worker, leading to lost updates. I've also tried using Redis transactions with `MULTI`/`EXEC`, but that doesn't seem to handle the locking as expected. Am I missing something fundamentally in how I should structure my access to Redis when using multiple workers? What are the best practices for managing shared state in a clustered Node.js environment? This is part of a larger microservice I'm building. What am I doing wrong?