66 lines
2.1 KiB
JavaScript
66 lines
2.1 KiB
JavaScript
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// Copyright (c) 2012 Mathieu Turcotte
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// Licensed under the MIT license.
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var events = require('events');
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var precond = require('precond');
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var util = require('util');
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// A class to hold the state of a backoff operation. Accepts a backoff strategy
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// to generate the backoff delays.
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function Backoff(backoffStrategy) {
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events.EventEmitter.call(this);
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this.backoffStrategy_ = backoffStrategy;
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this.maxNumberOfRetry_ = -1;
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this.backoffNumber_ = 0;
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this.backoffDelay_ = 0;
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this.timeoutID_ = -1;
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this.handlers = {
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backoff: this.onBackoff_.bind(this)
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};
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}
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util.inherits(Backoff, events.EventEmitter);
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// Sets a limit, greater than 0, on the maximum number of backoffs. A 'fail'
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// event will be emitted when the limit is reached.
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Backoff.prototype.failAfter = function(maxNumberOfRetry) {
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precond.checkArgument(maxNumberOfRetry > 0,
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'Expected a maximum number of retry greater than 0 but got %s.',
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maxNumberOfRetry);
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this.maxNumberOfRetry_ = maxNumberOfRetry;
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};
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// Starts a backoff operation. Accepts an optional parameter to let the
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// listeners know why the backoff operation was started.
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Backoff.prototype.backoff = function(err) {
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precond.checkState(this.timeoutID_ === -1, 'Backoff in progress.');
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if (this.backoffNumber_ === this.maxNumberOfRetry_) {
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this.emit('fail', err);
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this.reset();
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} else {
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this.backoffDelay_ = this.backoffStrategy_.next();
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this.timeoutID_ = setTimeout(this.handlers.backoff, this.backoffDelay_);
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this.emit('backoff', this.backoffNumber_, this.backoffDelay_, err);
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}
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};
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// Handles the backoff timeout completion.
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Backoff.prototype.onBackoff_ = function() {
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this.timeoutID_ = -1;
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this.emit('ready', this.backoffNumber_, this.backoffDelay_);
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this.backoffNumber_++;
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};
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// Stops any backoff operation and resets the backoff delay to its inital value.
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Backoff.prototype.reset = function() {
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this.backoffNumber_ = 0;
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this.backoffStrategy_.reset();
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clearTimeout(this.timeoutID_);
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this.timeoutID_ = -1;
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};
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module.exports = Backoff;
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