twilio-video/lib/util/backoff.js

Twilio Video JavaScript Library

/**
 * Expose `Backoff`.
 */

class Backoff {
  /**
   * Construct a {@link Backoff}.
   * @param {object} options
   * @property {number} min - Initial timeout in milliseconds [100]
   * @property {number} max - Max timeout [10000]
   * @property {boolean} jitter - Apply jitter [0]
   * @property {number} factor - Multiplication factor for Backoff operation [2]
   */
  constructor(options) {
    Object.defineProperties(this, {
      _min: {
        value: options.min || 100
      },
      _max: {
        value: options.max || 10000
      },
      _jitter: {
        value: options.jitter > 0 && options.jitter <= 1 ? options.jitter : 0
      },
      _factor: {
        value: options.factor || 2
      },
      _attempts: {
        value: 0,
        writable: true
      },
      _duration: {
        enumerable: false,
        get() {
          let ms = this._min * Math.pow(this._factor, this._attempts);
          if (this._jitter) {
            const rand =  Math.random();
            const deviation = Math.floor(rand * this._jitter * ms);
            ms = (Math.floor(rand * 10) & 1) === 0  ? ms - deviation : ms + deviation;
          }
          return Math.min(ms, this._max) | 0;
        }
      },
      _timeoutID: {
        value: null,
        writable: true
      }
    });
  }

  /**
  * Start the backoff operation.
  * @param {function} fn - Function to call
  * @return {void}
  * @api public
  */
  backoff(fn) {
    let duration = this._duration;
    if (this._timeoutID) {
      clearTimeout(this._timeoutID);
      this._timeoutID = null;
    }
    this._timeoutID = setTimeout(() => {
      this._attempts++;
      fn();
    }, duration);
  }

  /**
  * Reset the number of attempts and clear the timer.
  *
  * @return {void}
  * @api public
  */
  reset() {
    this._attempts = 0;
    if (this._timeoutID) {
      clearTimeout(this._timeoutID);
      this._timeoutID = null;
    }
  }
}

module.exports = Backoff;