Implementing CPU usage calculation

stats.js

@@ -1,5 +1,36 @@
 'use strict'
 
+var os = require('os')
+
+var startMeasure = cpuAverage()
+
+function cpuAverage () {
+  var totalIdle = 0
+  var totalTick = 0
+  var cpus = os.cpus()
+  for (var i = 0, len = cpus.length; i < len; i++) {
+    var cpu = cpus[i]
+    for (var type in cpu.times) {
+      totalTick += cpu.times[type]
+    }
+    totalIdle += cpu.times.idle
+  }
+  return {
+    idle: totalIdle / cpus.length,
+    total: totalTick / cpus.length
+  }
+}
+
+var cpuUsageInterval = setInterval(cpuCalculation, 1000)
+
+function cpuCalculation () {
+  var endMeasure = cpuAverage()
+  var idleDifference = endMeasure.idle - startMeasure.idle
+  var totalDifference = endMeasure.total - startMeasure.total
+  var cpuPercentage = 100 - ~~(100 * idleDifference / totalDifference)
+  this.stats.cpuUsage = cpuPercentage
+}
+
 function client () {
   this.stats.connectedClients++
   if (this.stats.connectedClients > this.stats.maxConnectedClients) {
@@ -35,7 +66,8 @@ function wire (aedesInstance, options) {
     connectedClients: 0,
     publishedMessages: 0,
     started: new Date(),
-    time: new Date()
+    time: new Date(),
+    cpuUsage: 0,
   }
 
   function doPub (topic, value) {
@@ -61,6 +93,7 @@ function wire (aedesInstance, options) {
     doPub('messages/publish/sent', stats.publishedMessages)
     doPub('memory/heap/current', mem.heapUsed)
     doPub('memory/heap/maximum', mem.heapTotal)
+    doPub('cpu/usage', stats.cpuUsage)
   }
 
   aedesEvents.forEach(function (event) {