Notifying when using high CPU. Via AppleScript or Automator? - macos

Question

I'd like to automate that whenever a process is using more than 50% CPU
it sends a notification to my Notification Center
I'm using terminal-notifier for sending trough notifications
but I'm a bit stuck on what the best method is for creating this automation.
Should I use Automator.app or create a custom AppleScript and if so,
how do I make it to always be on?

Answer 1

If this is for interactive use, let me suggest a pragmatic alternative:
Run Activity Monitor.
Control-click its dock icon.
Select Dock Icon > Show CPU Usage - or, for a floating window, Monitors > Show CPU Usage.
You'll get a per-core display of current CPU usage - clicking on it will show the full Activity Monitor window, where you can sort by CPU usage.
If you do need an automated solution, I suggest:
writing a bash script that uses top to find the highest-CPU-percentage task and invokes terminal-notifier, if above the threshold.
scheduling that script as a launchd task for periodic invocation.
Automator and AppleScript are probably too heavy for such - presumably frequent - background activity.
Even running top itself uses quite a bit of CPU.
Here's a simple bash script that roughly does what you want:
#!/usr/bin/env bash
read pct name < <(top -l 2 -n 1 -F -o cpu -stats cpu,command | tail -1)
if (( ${pct%.*} >= 50 )); then
/Applications/terminal-notifier.app/Contents/MacOS/terminal-notifier \
-message "Process > 50%: $name ($pct%)"
fi
Note that this takes at least 2 seconds to run, because 2 samples (1 second apart) must be collected to calculate CPU-usage percentages, so consider that when determining how frequently to invoke the command.
Update - see below for step-by-step implementation instructions.
References:
As for scheduling the script to have launchd run it on login: see https://stackoverflow.com/a/22872222/45375
The general format of launchd *.plist files is described at https://developer.apple.com/library/mac/documentation/Darwin/Reference/Manpages/man5/launchd.plist.5.html or man launchd.plist; StartInterval is the key for specifying invocations every N seconds.
Step-by-step instructions for implementing the automated solution:
Create the bash script:
Create plain-text file ~/watchcpu (i.e., file watchcpu in your home folder), paste the above bash script into it, and save it.
Create the per-user launch agent for invocation at login and periodic invocation thereafter:
Create plain-text file ~/Library/LaunchAgents/WatchCPU.plist, paste the following XML document into it, and save it:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>KeepAlive</key>
<false/>
<key>Label</key>
<string>WatchCPU</string>
<key>ProgramArguments</key>
<array>
<string>bash</string>
<string>-c</string>
<string>. ~/watchcpu</string>
</array>
<key>RunAtLoad</key>
<true/>
<key>StartInterval</key>
<integer>15</integer>
</dict>
</plist>
Load the per-user launch agent to activate it:
Run the following command in Terminal (only needed once; from then on, the file will auto-load on every login):
launchctl load ~/Library/LaunchAgents/WatchCPU.plist
Note:
You're free to choose your own filenames and a different location for your bash script, but the launch agent .plist file MUST reside in ~/Library/LaunchAgents in order to be loaded automatically at login.
The interval (key StartInterval) is chosen at 15 seconds; again, you're free to change that, but note that choosing more frequent invocations doesn't make much sense, because launchd (the service that invokes launch agents) throttles agents whose execution time is too close to the invocation interval; I'm unclear on the details, but in the solution at hand an interval of 10 seconds results in frequent throttling notices in system.log (check via Console.app).

Answer 2

You can easily pull the CPU usage to use either with a script or in an Automator workflow. Here's a script that you can schedule to run on a schedule and will notify if usage is over 50%:
set theDelay to 3 -- number of seconds to sample the CPU
set CPUusage to do shell script "top -F -l " & theDelay & " -n 1 -stats cpu | grep 'CPU usage:' | tail -1 | cut -d. -f1"
set idlePercent to word -2 of CPUusage as number
if idlePercent < 50 then display notification ("CPU usage is at " & (100 - idlePercent) & "%.") with title "CPU Usage"
See the comments to follow the editing of the do shell script command to allow for getting the integer naturally from the shell command to work better with non-English systems.