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    index.js backoff.js function_call.js exponential.js fibonacci.js strategy.js

  • strategy.js

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

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

function isDef(value) {
    return value !== undefined && value !== null;
}
  • ¶

    Abstract class defining the skeleton for the backoff strategies. Accepts an object holding the options for the backoff strategy:

    • randomisationFactor: The randomisation factor which must be between 0 and 1 where 1 equates to a randomization factor of 100% and 0 to no randomization.
    • initialDelay: The backoff initial delay in milliseconds.
    • maxDelay: The backoff maximal delay in milliseconds.
    function BackoffStrategy(options) {
    options = options || {};

    if (isDef(options.initialDelay) && options.initialDelay < 1) {
        throw new Error('The initial timeout must be greater than 0.');
    } else if (isDef(options.maxDelay) && options.maxDelay < 1) {
        throw new Error('The maximal timeout must be greater than 0.');
    }

    this.initialDelay_ = options.initialDelay || 100;
    this.maxDelay_ = options.maxDelay || 10000;

    if (this.maxDelay_ <= this.initialDelay_) {
        throw new Error('The maximal backoff delay must be ' +
                        'greater than the initial backoff delay.');
    }

    if (isDef(options.randomisationFactor) &&
        (options.randomisationFactor < 0 || options.randomisationFactor > 1)) {
        throw new Error('The randomisation factor must be between 0 and 1.');
    }

    this.randomisationFactor_ = options.randomisationFactor || 0;
}
  • ¶

    Gets the maximal backoff delay.

    BackoffStrategy.prototype.getMaxDelay = function() {
    return this.maxDelay_;
};
  • ¶

    Gets the initial backoff delay.

    BackoffStrategy.prototype.getInitialDelay = function() {
    return this.initialDelay_;
};
  • ¶

    Template method that computes and returns the next backoff delay in milliseconds.

    BackoffStrategy.prototype.next = function() {
    var backoffDelay = this.next_();
    var randomisationMultiple = 1 + Math.random() * this.randomisationFactor_;
    var randomizedDelay = Math.round(backoffDelay * randomisationMultiple);
    return randomizedDelay;
};
  • ¶

    Computes and returns the next backoff delay. Intended to be overridden by subclasses.

    BackoffStrategy.prototype.next_ = function() {
    throw new Error('BackoffStrategy.next_() unimplemented.');
};
  • ¶

    Template method that resets the backoff delay to its initial value.

    BackoffStrategy.prototype.reset = function() {
    this.reset_();
};
  • ¶

    Resets the backoff delay to its initial value. Intended to be overridden by subclasses.

    BackoffStrategy.prototype.reset_ = function() {
    throw new Error('BackoffStrategy.reset_() unimplemented.');
};

module.exports = BackoffStrategy;