Fail to export redis to different files in express

When I npm start the express server and go to localhost:3000/
There will be error message: (node:6984) UnhandledPromiseRejectionWarning: Error: The client is closed
The redisClient will be working when I put the createClient() in App.js, however, I want to make connect to the redis once and all files able establish the same connection

How to namespace keys on redis to avoid name collisions?

I want to use redis to store some of my own key-value pairs, however some of my modules already use it. The redis express session store for session data, as well as the redis adapter for socket io. So my question is simple, how can I create or designate a database/namespace to store my own keys without key collisions? I am using the node-redis driver.

Efficient way redis set member update

I have a redis set. This set can store 20 members maximum(added withSADD command).
My problem is ; I need to update that members when needed. Members need that modification maximum 10 times for every member. Set members are json as a string. There is only solutoin on my mind nor, get all members update and recreate that set again. But it seems iditoic.