Source: components/agecounters.js

  1. "use strict";
  3. const HOUR = 3600;
  4. const DAY = HOUR * 24;
  5. const WEEK = DAY * 7;
  7. const PERIOD_UNITS = {
  8.     "h": HOUR,
  9.     "d": DAY,
  10.     "w": WEEK,
  11. };
  13. const PERIOD_UNIT_KEYS = Object.keys(PERIOD_UNITS);
  15. /**
  16.  * A small helper object that counts into buckets the number of calls to its
  17.  * <code>bump</code> that fall into the given age categories.
  18.  * Counts are maintained within the object, and can be fetched to set
  19.  * into a gauge metric object.
  20.  *
  21.  * This class is useful when exporting metrics that count the number of
  22.  * hourly/daily/weekly active instances of various types of object within the
  23.  * bridge.
  24.  */
  26. class AgeCounters {
  27.     /***
  28.      * @param {String[]} counterPeriods A set of strings denoting the bucket periods
  29.      * used by the gauge. It is in the format of '#X' where # is the integer period and
  30.      * X is the unit of time. A unit can be one of 'h, d, w' for hours, days and weeks.
  31.      * 7d would be 7 days. If not given, the periods are 1h, 1d and 7d.
  32.      */
  33.     constructor(counterPeriods) {
  34.         if (counterPeriods) {
  35.             counterPeriods = Array.from(counterPeriods);
  36.         }
  37.         counterPeriods = counterPeriods || ["1h", "1d", "7d"];
  38.         this.counters = new Map();
  39.         this.counterPeriods = counterPeriods;
  40.         counterPeriods.forEach((periodKey) => {
  41.             if (periodKey.length < 2) {
  42.                 throw Error("A period must contain a unit.");
  43.             }
  44.             const unit = periodKey[periodKey.length-1];
  45.             if (!PERIOD_UNIT_KEYS.includes(unit)) {
  46.                 throw Error(`The unit period must be one of '${PERIOD_UNIT_KEYS.join(",")}'`);
  47.             }
  48.             const number = parseInt(periodKey.substr(0, periodKey.length-1));
  49.             if (isNaN(number) || number <= 0) {
  50.                 throw Error("The period duration must be a positive integer.");
  51.             }
  52.             this.counters.set(number * PERIOD_UNITS[unit], 0);
  53.         });
  54.         this.counterPeriods.push("all");
  55.         this.counters.set("all", 0);
  56.     }
  58.     /**
  59.      * Increment the values of the internal counters depending on the given age,
  60.      * in seconds.
  61.      *
  62.      * @param {Number} age The age in seconds.
  63.      */
  64.     bump(age) {
  65.         this.counters.forEach((value, key) => {
  66.             if (key === "all") {
  67.                 this.counters.set("all", value + 1);
  68.             }
  69.             else if (age < key) {
  70.                 this.counters.set(key, value + 1);
  71.             }
  72.         });
  73.     }
  75.     /**
  76.      * Fetch the counts in the age buckets and set them as labeled observations in
  77.      * the given gauge metric instance.
  78.      *
  79.      * @param {Gauge} gauge The gauge metric instance.
  80.      * @param {Object} morelabels An object containing more labels to add to the
  81.      * gauge when setting values.
  82.      */
  83.     setGauge(gauge, morelabels) {
  84.         const counters = this.counters;
  85.         let i = 0;
  86.         counters.forEach((value) => {
  87.             const labels = Object.assign(
  88.                 {
  89.                     age: this.counterPeriods[i]
  90.                 },
  91.                 morelabels
  92.             );
  93.             gauge.set(labels, value);
  94.             i++;
  95.         });
  96.     }
  97. }
  99. module.exports = AgeCounters;