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<!DOCTYPE html>
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<div class="annotation">
<h1>function_call.js</h1>
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<li id="section-1">
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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>);
<span class="hljs-keyword">var</span> Backoff = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./backoff'</span>);
<span class="hljs-keyword">var</span> FibonacciBackoffStrategy = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./strategy/fibonacci'</span>);</pre></div></div>
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<p>Wraps a function to be called in a backoff loop.</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">FunctionCall</span><span class="hljs-params">(fn, args, callback)</span> {</span>
events.EventEmitter.call(<span class="hljs-keyword">this</span>);
precond.checkIsFunction(fn, <span class="hljs-string">'Expected fn to be a function.'</span>);
precond.checkIsArray(args, <span class="hljs-string">'Expected args to be an array.'</span>);
precond.checkIsFunction(callback, <span class="hljs-string">'Expected callback to be a function.'</span>);
<span class="hljs-keyword">this</span>.function_ = fn;
<span class="hljs-keyword">this</span>.arguments_ = args;
<span class="hljs-keyword">this</span>.callback_ = callback;
<span class="hljs-keyword">this</span>.lastResult_ = [];
<span class="hljs-keyword">this</span>.numRetries_ = <span class="hljs-number">0</span>;
<span class="hljs-keyword">this</span>.backoff_ = <span class="hljs-literal">null</span>;
<span class="hljs-keyword">this</span>.strategy_ = <span class="hljs-literal">null</span>;
<span class="hljs-keyword">this</span>.failAfter_ = -<span class="hljs-number">1</span>;
<span class="hljs-keyword">this</span>.state_ = FunctionCall.State_.PENDING;
}
util.inherits(FunctionCall, events.EventEmitter);</pre></div></div>
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<p>States in which the call can be.</p>
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<div class="content"><div class='highlight'><pre>FunctionCall.State_ = {</pre></div></div>
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<p>Call isn’t started yet.</p>
</div>
<div class="content"><div class='highlight'><pre> PENDING: <span class="hljs-number">0</span>,</pre></div></div>
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<p>Call is in progress.</p>
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<div class="content"><div class='highlight'><pre> RUNNING: <span class="hljs-number">1</span>,</pre></div></div>
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<p>Call completed successfully which means that either the wrapped function
returned successfully or the maximal number of backoffs was reached.</p>
</div>
<div class="content"><div class='highlight'><pre> COMPLETED: <span class="hljs-number">2</span>,</pre></div></div>
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<p>The call was aborted.</p>
</div>
<div class="content"><div class='highlight'><pre> ABORTED: <span class="hljs-number">3</span>
};</pre></div></div>
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<p>Checks whether the call is pending.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.isPending = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.state_ == FunctionCall.State_.PENDING;
};</pre></div></div>
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<p>Checks whether the call is in progress.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.isRunning = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.state_ == FunctionCall.State_.RUNNING;
};</pre></div></div>
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<p>Checks whether the call is completed.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.isCompleted = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.state_ == FunctionCall.State_.COMPLETED;
};</pre></div></div>
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<p>Checks whether the call is aborted.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.isAborted = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.state_ == FunctionCall.State_.ABORTED;
};</pre></div></div>
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<p>Sets the backoff strategy to use. Can only be called before the call is
started otherwise an exception will be thrown.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.setStrategy = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(strategy)</span> {</span>
precond.checkState(<span class="hljs-keyword">this</span>.isPending(), <span class="hljs-string">'FunctionCall in progress.'</span>);
<span class="hljs-keyword">this</span>.strategy_ = strategy;
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>; <span class="hljs-comment">// Return this for chaining.</span>
};</pre></div></div>
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<p>Returns all intermediary results returned by the wrapped function since
the initial call.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.getLastResult = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.lastResult_.concat();
};</pre></div></div>
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<p>Returns the number of times the wrapped function call was retried.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.getNumRetries = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.numRetries_;
};</pre></div></div>
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<p>Sets the backoff limit.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.failAfter = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(maxNumberOfRetry)</span> {</span>
precond.checkState(<span class="hljs-keyword">this</span>.isPending(), <span class="hljs-string">'FunctionCall in progress.'</span>);
<span class="hljs-keyword">this</span>.failAfter_ = maxNumberOfRetry;
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>; <span class="hljs-comment">// Return this for chaining.</span>
};</pre></div></div>
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<p>Aborts the call.</p>
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<div class="content"><div class='highlight'><pre>FunctionCall.prototype.abort = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
precond.checkState(!<span class="hljs-keyword">this</span>.isCompleted(), <span class="hljs-string">'FunctionCall already completed.'</span>);
<span class="hljs-keyword">if</span> (<span class="hljs-keyword">this</span>.isRunning()) {
<span class="hljs-keyword">this</span>.backoff_.reset();
}
<span class="hljs-keyword">this</span>.state_ = FunctionCall.State_.ABORTED;
};</pre></div></div>
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<p>Initiates the call to the wrapped function. Accepts an optional factory
function used to create the backoff instance; used when testing.</p>
</div>
<div class="content"><div class='highlight'><pre>FunctionCall.prototype.start = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(backoffFactory)</span> {</span>
precond.checkState(!<span class="hljs-keyword">this</span>.isAborted(), <span class="hljs-string">'FunctionCall aborted.'</span>);
precond.checkState(<span class="hljs-keyword">this</span>.isPending(), <span class="hljs-string">'FunctionCall already started.'</span>);
<span class="hljs-keyword">var</span> strategy = <span class="hljs-keyword">this</span>.strategy_ || <span class="hljs-keyword">new</span> FibonacciBackoffStrategy();
<span class="hljs-keyword">this</span>.backoff_ = backoffFactory ?
backoffFactory(strategy) :
<span class="hljs-keyword">new</span> Backoff(strategy);
<span class="hljs-keyword">this</span>.backoff_.on(<span class="hljs-string">'ready'</span>, <span class="hljs-keyword">this</span>.doCall_.bind(<span class="hljs-keyword">this</span>, <span class="hljs-literal">true</span> <span class="hljs-comment">/* isRetry */</span>));
<span class="hljs-keyword">this</span>.backoff_.on(<span class="hljs-string">'fail'</span>, <span class="hljs-keyword">this</span>.doCallback_.bind(<span class="hljs-keyword">this</span>));
<span class="hljs-keyword">this</span>.backoff_.on(<span class="hljs-string">'backoff'</span>, <span class="hljs-keyword">this</span>.handleBackoff_.bind(<span class="hljs-keyword">this</span>));
<span class="hljs-keyword">if</span> (<span class="hljs-keyword">this</span>.failAfter_ > <span class="hljs-number">0</span>) {
<span class="hljs-keyword">this</span>.backoff_.failAfter(<span class="hljs-keyword">this</span>.failAfter_);
}
<span class="hljs-keyword">this</span>.state_ = FunctionCall.State_.RUNNING;
<span class="hljs-keyword">this</span>.doCall_(<span class="hljs-literal">false</span> <span class="hljs-comment">/* isRetry */</span>);
};</pre></div></div>
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<p>Calls the wrapped function.</p>
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<div class="content"><div class='highlight'><pre>FunctionCall.prototype.doCall_ = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(isRetry)</span> {</span>
<span class="hljs-keyword">if</span> (isRetry) {
<span class="hljs-keyword">this</span>.numRetries_++;
}
<span class="hljs-keyword">var</span> eventArgs = [<span class="hljs-string">'call'</span>].concat(<span class="hljs-keyword">this</span>.arguments_);
events.EventEmitter.prototype.emit.apply(<span class="hljs-keyword">this</span>, eventArgs);
<span class="hljs-keyword">var</span> callback = <span class="hljs-keyword">this</span>.handleFunctionCallback_.bind(<span class="hljs-keyword">this</span>);
<span class="hljs-keyword">this</span>.function_.apply(<span class="hljs-literal">null</span>, <span class="hljs-keyword">this</span>.arguments_.concat(callback));
};</pre></div></div>
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<p>Calls the wrapped function’s callback with the last result returned by the
wrapped function.</p>
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<div class="content"><div class='highlight'><pre>FunctionCall.prototype.doCallback_ = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">this</span>.callback_.apply(<span class="hljs-literal">null</span>, <span class="hljs-keyword">this</span>.lastResult_);
};</pre></div></div>
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<p>Handles wrapped function’s completion. This method acts as a replacement
for the original callback function.</p>
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<div class="content"><div class='highlight'><pre>FunctionCall.prototype.handleFunctionCallback_ = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">if</span> (<span class="hljs-keyword">this</span>.isAborted()) {
<span class="hljs-keyword">return</span>;
}
<span class="hljs-keyword">var</span> args = <span class="hljs-built_in">Array</span>.prototype.slice.call(<span class="hljs-built_in">arguments</span>);
<span class="hljs-keyword">this</span>.lastResult_ = args; <span class="hljs-comment">// Save last callback arguments.</span>
events.EventEmitter.prototype.emit.apply(<span class="hljs-keyword">this</span>, [<span class="hljs-string">'callback'</span>].concat(args));
<span class="hljs-keyword">if</span> (args[<span class="hljs-number">0</span>]) {
<span class="hljs-keyword">this</span>.backoff_.backoff(args[<span class="hljs-number">0</span>]);
} <span class="hljs-keyword">else</span> {
<span class="hljs-keyword">this</span>.state_ = FunctionCall.State_.COMPLETED;
<span class="hljs-keyword">this</span>.doCallback_();
}
};</pre></div></div>
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<p>Handles the backoff event by reemitting it.</p>
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<div class="content"><div class='highlight'><pre>FunctionCall.prototype.handleBackoff_ = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(number, delay, err)</span> {</span>
<span class="hljs-keyword">this</span>.emit(<span class="hljs-string">'backoff'</span>, number, delay, err);
};
module.exports = FunctionCall;</pre></div></div>
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