HORIZON PROJECT

/**

 * Expose `Backoff`.

 */

module.exports = Backoff;

/**

 * Initialize backoff timer with `opts`.

 *

 * - `min` initial timeout in milliseconds [100]

 * - `max` max timeout [10000]

 * - `jitter` [0]

 * - `factor` [2]

 *

 * @param {Object} opts

 * @api public

 */

function Backoff(opts) {

  opts = opts || {};

  this.ms = opts.min || 100;

  this.max = opts.max || 10000;

  this.factor = opts.factor || 2;

  this.jitter = opts.jitter > 0 && opts.jitter <= 1 ? opts.jitter : 0;

  this.attempts = 0;

}

/**

 * Return the backoff duration.

 *

 * @return {Number}

 * @api public

 */

Backoff.prototype.duration = function(){

  var ms = this.ms * Math.pow(this.factor, this.attempts++);

  if (this.jitter) {

    var rand =  Math.random();

    var 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;

};

/**

 * Reset the number of attempts.

 *

 * @api public

 */

Backoff.prototype.reset = function(){

  this.attempts = 0;

};

/**

 * Set the minimum duration

 *

 * @api public

 */

Backoff.prototype.setMin = function(min){

  this.ms = min;

};

/**

 * Set the maximum duration

 *

 * @api public

 */

Backoff.prototype.setMax = function(max){

  this.max = max;

};

/**

 * Set the jitter

 *

 * @api public

 */

Backoff.prototype.setJitter = function(jitter){

  this.jitter = jitter;

};