om/node_modules/backoff/lib/strategy/exponential.js

//      Copyright (c) 2012 Mathieu Turcotte
//      Licensed under the MIT license.

var util = require('util');
var precond = require('precond');

var BackoffStrategy = require('./strategy');

// Exponential backoff strategy.
function ExponentialBackoffStrategy(options) {
    BackoffStrategy.call(this, options);
    this.backoffDelay_ = 0;
    this.nextBackoffDelay_ = this.getInitialDelay();
    this.factor_ = ExponentialBackoffStrategy.DEFAULT_FACTOR;

    if (options && options.factor !== undefined) {
        precond.checkArgument(options.factor > 1,
            'Exponential factor should be greater than 1 but got %s.',
            options.factor);
        this.factor_ = options.factor;
    }
}
util.inherits(ExponentialBackoffStrategy, BackoffStrategy);

// Default multiplication factor used to compute the next backoff delay from
// the current one. The value can be overridden by passing a custom factor as
// part of the options.
ExponentialBackoffStrategy.DEFAULT_FACTOR = 2;

ExponentialBackoffStrategy.prototype.next_ = function() {
    this.backoffDelay_ = Math.min(this.nextBackoffDelay_, this.getMaxDelay());
    this.nextBackoffDelay_ = this.backoffDelay_ * this.factor_;
    return this.backoffDelay_;
};

ExponentialBackoffStrategy.prototype.reset_ = function() {
    this.backoffDelay_ = 0;
    this.nextBackoffDelay_ = this.getInitialDelay();
};

module.exports = ExponentialBackoffStrategy;