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<h1>backoff.js</h1>
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<pre><code> Copyright (c) <span class="hljs-number">2012</span> Mathieu Turcotte
Licensed under the MIT license.
</code></pre>
</div>
<div class="content"><div class='highlight'><pre>
<span class="hljs-keyword">var</span> events = <span class="hljs-built_in">require</span>(<span class="hljs-string">'events'</span>);
<span class="hljs-keyword">var</span> precond = <span class="hljs-built_in">require</span>(<span class="hljs-string">'precond'</span>);
<span class="hljs-keyword">var</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>);</pre></div></div>
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<p>A class to hold the state of a backoff operation. Accepts a backoff strategy
to generate the backoff delays.</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">Backoff</span><span class="hljs-params">(backoffStrategy)</span> {</span>
events.EventEmitter.call(<span class="hljs-keyword">this</span>);
<span class="hljs-keyword">this</span>.backoffStrategy_ = backoffStrategy;
<span class="hljs-keyword">this</span>.maxNumberOfRetry_ = -<span class="hljs-number">1</span>;
<span class="hljs-keyword">this</span>.backoffNumber_ = <span class="hljs-number">0</span>;
<span class="hljs-keyword">this</span>.backoffDelay_ = <span class="hljs-number">0</span>;
<span class="hljs-keyword">this</span>.timeoutID_ = -<span class="hljs-number">1</span>;
<span class="hljs-keyword">this</span>.handlers = {
backoff: <span class="hljs-keyword">this</span>.onBackoff_.bind(<span class="hljs-keyword">this</span>)
};
}
util.inherits(Backoff, events.EventEmitter);</pre></div></div>
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<p>Sets a limit, greater than 0, on the maximum number of backoffs. A ‘fail’
event will be emitted when the limit is reached.</p>
</div>
<div class="content"><div class='highlight'><pre>Backoff.prototype.failAfter = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(maxNumberOfRetry)</span> {</span>
precond.checkArgument(maxNumberOfRetry > <span class="hljs-number">0</span>,
<span class="hljs-string">'Expected a maximum number of retry greater than 0 but got %s.'</span>,
maxNumberOfRetry);
<span class="hljs-keyword">this</span>.maxNumberOfRetry_ = maxNumberOfRetry;
};</pre></div></div>
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<p>Starts a backoff operation. Accepts an optional parameter to let the
listeners know why the backoff operation was started.</p>
</div>
<div class="content"><div class='highlight'><pre>Backoff.prototype.backoff = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(err)</span> {</span>
precond.checkState(<span class="hljs-keyword">this</span>.timeoutID_ === -<span class="hljs-number">1</span>, <span class="hljs-string">'Backoff in progress.'</span>);
<span class="hljs-keyword">if</span> (<span class="hljs-keyword">this</span>.backoffNumber_ === <span class="hljs-keyword">this</span>.maxNumberOfRetry_) {
<span class="hljs-keyword">this</span>.emit(<span class="hljs-string">'fail'</span>, err);
<span class="hljs-keyword">this</span>.reset();
} <span class="hljs-keyword">else</span> {
<span class="hljs-keyword">this</span>.backoffDelay_ = <span class="hljs-keyword">this</span>.backoffStrategy_.next();
<span class="hljs-keyword">this</span>.timeoutID_ = setTimeout(<span class="hljs-keyword">this</span>.handlers.backoff, <span class="hljs-keyword">this</span>.backoffDelay_);
<span class="hljs-keyword">this</span>.emit(<span class="hljs-string">'backoff'</span>, <span class="hljs-keyword">this</span>.backoffNumber_, <span class="hljs-keyword">this</span>.backoffDelay_, err);
}
};</pre></div></div>
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<p>Handles the backoff timeout completion.</p>
</div>
<div class="content"><div class='highlight'><pre>Backoff.prototype.onBackoff_ = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">this</span>.timeoutID_ = -<span class="hljs-number">1</span>;
<span class="hljs-keyword">this</span>.emit(<span class="hljs-string">'ready'</span>, <span class="hljs-keyword">this</span>.backoffNumber_, <span class="hljs-keyword">this</span>.backoffDelay_);
<span class="hljs-keyword">this</span>.backoffNumber_++;
};</pre></div></div>
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<p>Stops any backoff operation and resets the backoff delay to its inital value.</p>
</div>
<div class="content"><div class='highlight'><pre>Backoff.prototype.reset = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">this</span>.backoffNumber_ = <span class="hljs-number">0</span>;
<span class="hljs-keyword">this</span>.backoffStrategy_.reset();
clearTimeout(<span class="hljs-keyword">this</span>.timeoutID_);
<span class="hljs-keyword">this</span>.timeoutID_ = -<span class="hljs-number">1</span>;
};
module.exports = Backoff;</pre></div></div>
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