Cron job vs NodeJS setInterval for optimal performance

cronnode.jsraspbian

I'm building a simple nodejs script that updates a DNS record based on my current IP. The script works fine but I have some concerns regarding how should I run it. The check for my IP must be performed every 5 minutes and I'm facing a dilemma.

Should I use Node's setInterval or should I create a cron job? Which will consume the least RAM and CPU? Please keep in mind that the script runs on a Raspberry Pi Zero with 512MB ram and only 1 core.

I know that the cron seems a better option but how much better is it? Does it matter given my specs?

Best Answer

Advantages of cron solution

less memory consumption for 90% of the time
memory leaks are effectively eliminted
the code is reloading all libraries every time so updates take effect on the next run without additional complexity

Advantages of daemon solution

load time only happens once so disk I/O and CPU are lower for subsequent runs since you won't be parsing your source code or pulling in all of the libraries
the lower CPU and disk I/O for subsequent runs also means that there is more of those resources available for whatever your main application for the Raspberry may be.
Linux should swap out the memory you're not using. This could be really slow depending on your storage though.

Conclusion

I agree with Alexander T that cron seems likely to be better, but if your main app is sensitive to background processes it might be better to go with the daemon.

Related Solutions

Cron Job – How to Run a Cron Job Manually and Immediately

Here's what I did, and it seems to work in this situation. At least, it shows me an error, whereas running from the command line as the user doesn't show the error.

Step 1: I put this line temporarily in the user's crontab:

* * * * *   /usr/bin/env > /home/username/tmp/cron-env

then took it out once the file was written.

Step 2: Made myself a little run-as-cron bash script containing:

#!/bin/bash
/usr/bin/env -i $(cat /home/username/tmp/cron-env) "$@"

So then, as the user in question, I was able to

run-as-cron /the/problematic/script --with arguments --and parameters

This solution could obviously be expanded to make use of sudo or such for more flexibility.

Hope this helps others.

Cron Job for FTP download

You can do a wget every sunday. With the login and the FTP password on the line, the download starts automatically. You can do a mirror to download only the differences, and do a tar or what you want after the download.

Make a small script, and ask cron to launch it every sunday.