I need to run a CPU- and memory-heavy Python script (analyzing and altering a lengthy WAV file) as a background process on my web server (a VPS), between HTTP requests.
The script takes up to 20 seconds to run and I am concerned about the performance on my server. Is there a good approach to either lower the priority of the process, periodically cede control to the OS, or otherwise protect the performance of my modest server?
Assuming it's a UNIX server, you could use the nice command to lower its priority. That should do the trick.
You can use cpulimit on a linux based server. It will allow you to limit the CPU usage (specify the limit as a percentage) even of scripts that have already started running, and its usage is pretty straightforward.
It's available on the Debian repository, so you can install it easily using aptitude:
apt-get install cpulimit
Typical ways to use cpulimit includes:
# To limit CPU usage to 75% of program called foo:
cpulimit -e foo -l 75
# To limit CPU usage to 50% of program with pid = 1582
cpulimit -p 1582 -l 50