Node.js Redis Singleton Connection + Auto-Reconnect Strategy

Problem

When multiple modules each call createClient(), you end up with duplicate Redis connections. Without reconnection logic, a network hiccup kills your app.

Solution

import { createClient, RedisClientType } from 'redis';

let redisClient: RedisClientType | null = null;
let isConnecting = false;

export async function getRedisClient(): Promise<RedisClientType> {
  // Return existing connection if open
  if (redisClient && redisClient.isOpen) {
    return redisClient;
  }

  // Wait if another caller is already connecting
  if (isConnecting) {
    while (isConnecting) {
      await new Promise(resolve => setTimeout(resolve, 100));
    }
    if (redisClient && redisClient.isOpen) return redisClient;
  }

  isConnecting = true;
  try {
    redisClient = createClient({
      url: process.env.REDIS_URL || 'redis://127.0.0.1:6379',
      socket: {
        reconnectStrategy: (retries) => {
          if (retries > 10) return new Error('Max retries reached');
          return Math.min(retries * 100, 3000); // exponential backoff
        }
      }
    });
    await redisClient.connect();
    return redisClient;
  } finally {
    isConnecting = false;
  }
}

Key Points

• The isConnecting flag prevents multiple simultaneous connect() calls. Without it, concurrent requests during startup create duplicate connections.
• reconnectStrategy uses retries * 100 for incremental delays (100ms, 200ms, 300ms…), capped at 3 seconds via Math.min. Gives up after 10 failures.
• The finally block ensures isConnecting is reset even on failure, allowing subsequent connection attempts.