spm-agent-nodejs/lib/eventLoopStats.js

Node.js monitoring agent for SPM by Sematext

/*
 * @copyright Copyright (c) Sematext Group, Inc. - All Rights Reserved
 *
 * @licence SPM for NodeJS is free-to-use, proprietary software.
 * THIS IS PROPRIETARY SOURCE CODE OF Sematext Group, Inc. (Sematext)
 * This source code may not be copied, reverse engineered, or altered for any purpose.
 * This source code is to be used exclusively by users and customers of Sematext.
 * Please see the full license (found in LICENSE in this distribution) for details on its license and the licenses of its dependencies.
 */

var util = require('util')
var events = require('events')

function EventLoopStats () {
  events.EventEmitter.call(this)
}
util.inherits(EventLoopStats, events.EventEmitter)

EventLoopStats.prototype.start = function () {
  var measures = [[0, 0]]
  var time = process.hrtime()
  var interval = 500
  this.measureInterval = setInterval(function () {
    measures.push(process.hrtime(time))
    if (measures.length === 2) {
      time = process.hrtime()
      measures[0] = [measures[0][0] - measures[1][0], measures[0][1] - measures[1][1]]
      measures[1] = [0, 0]
    }
  }, interval)

  this.reporterInterval = setInterval(function () {
    var timesInMicroSecs = measures.reduce(function (prev, value, i) {
      if (i > 0) {
        var diffInMicroSeconds = (measures[i][0] - measures[i - 1][0]) * 1e9 + (measures[i][1] - measures[i - 1][1])
        var key = Math.floor(diffInMicroSeconds - interval * 1e6) / 1e3
        // this means our timer was executed too early? -> negative delay, lets ignore dr. who phenomena in nodejs
        if (key < 0) {
          return prev
        }
        prev[key] = prev[key] || 0
        prev[key]++
      }
      return prev
    }, {})
    var stats = { count: 0, time: 0, avg: 0, min: 1e12, max: 0 }
    for (var key in timesInMicroSecs) {
      stats.time += parseInt(key, 10) * timesInMicroSecs[key]
      stats.count += timesInMicroSecs[key]
      stats.max = Math.max(parseInt(key, 10), stats.max)
      stats.min = Math.min(parseInt(key, 10), stats.min)
    }
    stats.avg = Math.floor(stats.time / stats.count)
    // console.log (stats)
    this.emit('data', stats)
    measures[0] = measures.pop()
    measures.length = 1
  }.bind(this), 10 * 1000)

  if (this.measureInterval.unref && this.reporterInterval.unref) {
    this.measureInterval.unref()
    this.reporterInterval.unref()
  }
}

EventLoopStats.prototype.stop = function () {
  if (this.measureInterval && this.reporterInterval) {
    clearInterval(this.measureInterval)
    clearInterval(this.reporterInterval)
  }
}

module.exports = new EventLoopStats()