remoting/webapp/base/js/stats_accumulator.js

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 /**
   6  * @fileoverview
   7  * The webapp reads the plugin's connection statistics frequently (once per
   8  * second). It logs statistics to the server less frequently, to keep
   9  * bandwidth and storage costs down. This class bridges that gap, by
  10  * accumulating high-frequency numeric data, and providing statistics
  11  * summarising that data.
  12  */
  13
  14 'use strict';
  15
  16 /** @suppress {duplicate} */
  17 var remoting = remoting || {};
  18
  19 /**
  20  * @constructor
  21  */
  22 remoting.StatsAccumulator = function() {
  23   /**
  24    * A map from names to lists of values.
  25    * @private {Object<Array<number>>}
  26    */
  27   this.valueLists_ = {};
  28
  29   /**
  30    * The first time, after this object was most recently initialized or emptied,
  31    * at which a value was added to this object.
  32    * @private {?number}
  33    */
  34   this.timeOfFirstValue_ = null;
  35 };
  36
  37 /**
  38  * Adds values to this object.
  39  *
  40  * @param {Object<number>} newValues
  41  */
  42 remoting.StatsAccumulator.prototype.add = function(newValues) {
  43   for (var key in newValues) {
  44     this.getValueList(key).push(newValues[key]);
  45   }
  46   if (this.timeOfFirstValue_ === null) {
  47     this.timeOfFirstValue_ = new Date().getTime();
  48   }
  49 };
  50
  51 /**
  52  * Empties this object.
  53  */
  54 remoting.StatsAccumulator.prototype.empty = function() {
  55   this.valueLists_ = {};
  56   this.timeOfFirstValue_ = null;
  57 };
  58
  59 /**
  60  * Gets the number of milliseconds since the first value was added to this
  61  * object, after this object was most recently initialized or emptied.
  62  *
  63  * @return {number} milliseconds since the first value
  64  */
  65 remoting.StatsAccumulator.prototype.getTimeSinceFirstValue = function() {
  66   if (this.timeOfFirstValue_ === null) {
  67     return 0;
  68   }
  69   return new Date().getTime() - this.timeOfFirstValue_;
  70 };
  71
  72 /**
  73  * Calculates the mean of the values for a given key.
  74  *
  75  * @param {string} key
  76  * @return {number} the mean of the values for that key
  77  */
  78 remoting.StatsAccumulator.prototype.calcMean = function(key) {
  79   /**
  80    * @param {Array<number>} values
  81    * @return {number}
  82    */
  83   var calcMean = function(values) {
  84     if (values.length == 0) {
  85       return 0.0;
  86     }
  87     var sum = 0;
  88     for (var i = 0; i < values.length; i++) {
  89       sum += values[i];
  90     }
  91     return sum / values.length;
  92   };
  93   return this.map(key, calcMean);
  94 };
  95
  96 /**
  97  * Applies a given map to the list of values for a given key.
  98  *
  99  * @param {string} key
 100  * @param {function(Array<number>): number} map
 101  * @return {number} the result of applying that map to the list of values for
 102  *     that key
 103  */
 104 remoting.StatsAccumulator.prototype.map = function(key, map) {
 105   return map(this.getValueList(key));
 106 };
 107
 108 /**
 109  * Gets the list of values for a given key.
 110  * If this object contains no values for that key, then this routine creates
 111  * an empty list, stores it in this object, and returns it.
 112  *
 113  * @private
 114  * @param {string} key
 115  * @return {Array<number>} the list of values for that key
 116  */
 117 remoting.StatsAccumulator.prototype.getValueList = function(key) {
 118   var valueList = this.valueLists_[key];
 119   if (!valueList) {
 120     valueList = [];
 121     this.valueLists_[key] = valueList;
 122   }
 123   return valueList;
 124 };
 125
 126 /**
 127  * @return {?remoting.ClientSession.PerfStats} returns null if all fields are
 128  *     zero.
 129  */
 130 remoting.StatsAccumulator.prototype.getPerfStats = function() {
 131   var stats = new remoting.ClientSession.PerfStats();
 132   stats.videoBandwidth = this.calcMean('videoBandwidth');
 133   stats.captureLatency = this.calcMean('captureLatency');
 134   stats.encodeLatency = this.calcMean('encodeLatency');
 135   stats.decodeLatency = this.calcMean('decodeLatency');
 136   stats.renderLatency = this.calcMean('renderLatency');
 137   stats.roundtripLatency = this.calcMean('roundtripLatency');
 138
 139   for (var key in stats) {
 140     if (stats[key] !== 0) {
 141       return stats;
 142     }
 143   }
 144   return null;
 145 };