Home Server autoStandby.js

If you want to wake up a server in your LAN you use Wake-on-lan, but what do you do if you want to automatically switch it off?

My situation is that I've a server which is also used as desktop to browse some internet pages, so some normal techniques doesn't apply:

desktop: GNOME/Unity/Ubuntu have built-in suspend after X minutes of inactivity (user level)
server: You can check if your cpu load is low and then pm-suspend it

Problems

If I'm downloading a file remotely via ssh + screen the desktop user is inactive so the computer is suspended by desktop suspend.
If I'm reading a page as desktop user the cpu load is low so the computer is suspended by the server script.

What to do?

Here is my solution: autoStandby.js . You need to disable desktop user level suspend and install 'xprintidle' utility (apt-get has it).

// autoStandby.js
var os = require('os');
// tick cicle

setInterval(function(){
// check low workload

var cpuload = os.loadavg()[2];

console.log(new Date()+ ' cpuload: ' +cpuload);

if (cpuload < 0.22) { // set your idle load, mine is 0.22
// check idle user
var exec = require('child_process').exec,
child;
child = exec('sudo -u your-desktop-user env DISPLAY=:0.0 xprintidle',
  function (error, stdout, stderr) {

    // do stanby
    console.log('xstdoutms: ' + stdout);
    var xidleMs = stdout;
    if (xidleMs &gt; 60 * 1000) {
      console.log('Goodbye crul world!!!');
      var exec = require('child_process').exec,
      child;
      child = exec('pm-suspend',
        function (error, stdout, stderr) {
          console.log('stdout: ' + stdout);
          console.log('stderr: ' + stderr);
          if (error !== null) {
            console.log('exec error: ' + error);
          }
      });
    }
    console.log('xstderr: ' + stderr);
    if (error !== null) {
      console.log('exec error: ' + error);
    }
});

}
}, 3 * 60 * 1000); // check every 3mins

Then you can run it with "node autoStanby.js" via screen, upstart or systemd.

Limitations

It runs as root
If the computer is used by more than one desktop user, the script must be tweaked
I know probably a bash version would be simpler, but I think to extend it in future with a web ui

What do you think? You have a better solution? Let me know it!