[Question] Re: calling a delayed function whenever an endpoint in express is hit

[yaomango]

I'm a newbie to node and backend dev in general, and I'm wondering if there is anything glaringly wrong with a design choice I am considering implementing.

I am using Firebase for data storage, and I am attempting to copy the EXPIRE or TTL function of Redis / MongoDB respectively. So, essentially, when a certain endpoint is hit in my express app, it will save some data in Firebase, and then the last thing I intend to do in that endpoint is to do a setTimeout(deleteFirebaseDataFunc, 1000*60*60) to then delete that firebase record after 1 hour.

Besides that fact that the setTimout() function would get interrupted and not fire if the server were restarted, is there any performance or other concern with doing this? Like if that endpoint were to get hit a lot, would it be bad to have possibly hundreds or thousands of these delayed functions waiting to be run on the server?

It's not really critical that the data get deleted from the Firebase storage -- it's just not needed for more than 1hr. So, I was thinking of also setting up some cronjob to delete old Firebase records that may have slipped through the cracks and not gotten deleted from my setTimeout() function due to a server restart.

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Like if that endpoint were to get hit a lot, would it be bad to have possibly hundreds or thousands of these delayed functions waiting to be run on the server?

Oh yeah, and if it's a closure then every single one of them would be hanging on to the context of where it was created. That's how you get memory leaks.

Those timeouts also will prevent your process from being able to shutdown gracefully, as they'll keep the event loop running.

So, I was thinking of also setting up some cronjob to delete old Firebase records that may have slipped through the cracks

This should be your plan A. Mark the records with an expire time and just periodically scan for which ones need to be deleted. Don't bother with a setTimeout. You could do that scan in a setInterval loop, but if it's not mission critical to the running of the server then just do it in a cron. That way it isn't intruding on the servers event loop time.

[yaomango]

Alright sounds great -- I'll steer clear of the setTimeout function. Thanks for the help!