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node_modules/backoff/lib/strategy/strategy.js

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+//      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;