next.js/examples/blog-with-comment/lib/redis.ts

import IORedis, { Redis } from "ioredis";

function fixUrl(url: string) {
  if (!url) {
    return "";
  }
  if (url.startsWith("redis://") && !url.startsWith("redis://:")) {
    return url.replace("redis://", "redis://:");
  }
  if (url.startsWith("rediss://") && !url.startsWith("rediss://:")) {
    return url.replace("rediss://", "rediss://:");
  }
  return url;
}

class ClientRedis {
  static instance: Redis;

  constructor() {
    throw new Error("Use Singleton.getInstance()");
  }

  static getInstance(): Redis | null {
    if (!ClientRedis.instance) {
      ClientRedis.instance = new IORedis(fixUrl(process.env.REDIS_URL!));
    }
    return ClientRedis.instance;
  }
}

export default ClientRedis.getInstance();