Persist setTimeout and setInterval across Node.js restarts

Question

I set quite a few server-side timeouts with setTimeout and setInterval for each connected user that can last for 10-30 seconds. If the Node.js instance restarts in the middle of one of these timeouts, they are obviously all cleared on restart, which can cause some issues for these users. How would I go about persisting these timeouts, or are there any modules that already help with this?

Answer 1

setTimeOut takes delay as parameter, so when setting timeout, capture currentServerTime + delay say serverTriggerTime and persist this in DB. Then, on restart of server, create the same timer using the serverTriggerTime. Then, delay = serverTriggerTime - currentServerTime, use this delay to set new timer.

When setting timer

const date = Date.now();
const serverTriggerTime = date + delay; // time in milliseconds

On server restart:

serverTriggerTime = // retrieve from DB.
newDelay = serverTriggerTime - Date.now();

Also, set new timer only if newDelay >= 0, meaning the trigger time has not reached and will happen after newDelay time.

Answer 2

I would store the start times and durations in Redis and restart incomplete timers when your application reloads. Some Redis modules:

https://github.com/joyent/node/wiki/modules#wiki-db-nosql-redis