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                 <h1>Node's goal is to provide an easy way to build scalable
               network programs</h1>


               <p>In the "hello world" web server example
               below, many client connections can be handled concurrently.
               Node tells the operating system (through <code>epoll</code>,
               <code>kqueue</code>, <code>/dev/poll</code>, or
               <code>select</code>) that it should be notified when a new
               connection is made, and then it goes to sleep. If someone new
               connects, then it executes the callback. Each connection is
               only a small heap allocation.</p>

               <pre>
 var http = require('http');
 http.createServer(function (req, res) {
   res.writeHead(200, {'Content-Type': 'text/plain'});
   res.end('Hello World\n');
 }).listen(1337, "127.0.0.1");
 console.log('Server running at http://127.0.0.1:1337/');</pre>
               <p>This is in contrast to today's more common concurrency
               model where OS threads are employed. Thread-based networking
               is relatively inefficient and very difficult to use. See: <a
                 href="http://www.kegel.com/c10k.html">this</a> and <a
                 href="http://bulk.fefe.de/scalable-networking.pdf">this</a>.
               Node will show much better memory efficiency under high-loads
               than systems which allocate 2mb thread stacks for each
               connection. Furthermore, users of Node are free from worries
               of dead-locking the process—there are no locks. Almost no
               function in Node directly performs I/O, so the process never
               blocks. Because nothing blocks, less-than-expert programmers
               are able to develop fast systems.</p>

               <p>Node is similar in design to and influenced by systems like
               Ruby's <a href="http://rubyeventmachine.com/">Event
                 Machine</a> or Python's <a
                 href="http://twistedmatrix.com/">Twisted</a>. Node takes the
               event model a bit further—it presents the event loop as a
               language construct instead of as a library. In other systems
               there is always a blocking call to start the event-loop.
               Typically one defines behavior through callbacks at the
               beginning of a script and at the end starts a server through a
               blocking call like <code>EventMachine::run()</code>. In Node
               there is no such start-the-event-loop call. Node simply enters
               the event loop after executing the input script. Node exits
               the event loop when there are no more callbacks to perform.
               This behavior is like browser javascript—the event loop is
               hidden from the user.</p>

               <p>HTTP is a first class protocol in Node. Node's HTTP library
               has grown out of the author's experiences developing and
               working with web servers. For example, streaming data through
               most web frameworks is impossible. Node attempts to correct
               these problems in its HTTP <a
               href="https://github.com/joyent/http-parser/tree/master">parser</a>
               and API. Coupled with Node's purely evented infrastructure, it
               makes a good foundation for web libraries or frameworks.</p>

               <p>But what about multiple-processor concurrency? Aren't
               threads necessary to scale programs to multi-core computers?
               You can start new processes via <code><a
               href="http://nodejs.org/api/child_process.html#child_process.fork">child_process.fork()</a></code>
               these other processes will be scheduled in parallel. For load
               balancing incoming connections across multiple processes use
               <a href="http://nodejs.org/api/cluster.html">the
               cluster module</a>.</p>

             <p>See also:</p>
             <ul>
                 <li><a href="http://s3.amazonaws.com/four.livejournal/20091117/jsconf.pdf">Slides from JSConf 2009</a></li>
                 <li><a href="http://nodejs.org/jsconf2010.pdf">Slides from JSConf 2010</a></li>
                 <li><a href="http://www.yuiblog.com/blog/2010/05/20/video-dahl/">Video from a talk at Yahoo in May 2010</a></li>
             </ul>
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	<div id="column1" class="interior">
	<h1>Node's goal is to provide an easy way to build scalable
	network programs</h1>


	<p>In the "hello world" web server example
	below, many client connections can be handled concurrently.
	Node tells the operating system (through <code>epoll</code>,
	<code>kqueue</code>, <code>/dev/poll</code>, or
	<code>select</code>) that it should be notified when a new
	connection is made, and then it goes to sleep. If someone new
	connects, then it executes the callback. Each connection is
	only a small heap allocation.</p>

	<pre>
	var http = require('http');
	http.createServer(function (req, res) {
	res.writeHead(200, {'Content-Type': 'text/plain'});
	res.end('Hello World\n');
	}).listen(1337, "127.0.0.1");
	console.log('Server running at http://127.0.0.1:1337/');</pre>
	<p>This is in contrast to today's more common concurrency
	model where OS threads are employed. Thread-based networking
	is relatively inefficient and very difficult to use. See: <a
	href="http://www.kegel.com/c10k.html">this</a> and <a
	href="http://bulk.fefe.de/scalable-networking.pdf">this</a>.
	Node will show much better memory efficiency under high-loads
	than systems which allocate 2mb thread stacks for each
	connection. Furthermore, users of Node are free from worries
	of dead-locking the process—there are no locks. Almost no
	function in Node directly performs I/O, so the process never
	blocks. Because nothing blocks, less-than-expert programmers
	are able to develop fast systems.</p>

	<p>Node is similar in design to and influenced by systems like
	Ruby's <a href="http://rubyeventmachine.com/">Event
	Machine</a> or Python's <a
	href="http://twistedmatrix.com/">Twisted</a>. Node takes the
	event model a bit further—it presents the event loop as a
	language construct instead of as a library. In other systems
	there is always a blocking call to start the event-loop.
	Typically one defines behavior through callbacks at the
	beginning of a script and at the end starts a server through a
	blocking call like <code>EventMachine::run()</code>. In Node
	there is no such start-the-event-loop call. Node simply enters
	the event loop after executing the input script. Node exits
	the event loop when there are no more callbacks to perform.
	This behavior is like browser javascript—the event loop is
	hidden from the user.</p>

	<p>HTTP is a first class protocol in Node. Node's HTTP library
	has grown out of the author's experiences developing and
	working with web servers. For example, streaming data through
	most web frameworks is impossible. Node attempts to correct
	these problems in its HTTP <a
	href="https://github.com/joyent/http-parser/tree/master">parser</a>
	and API. Coupled with Node's purely evented infrastructure, it
	makes a good foundation for web libraries or frameworks.</p>

	<p>But what about multiple-processor concurrency? Aren't
	threads necessary to scale programs to multi-core computers?
	You can start new processes via <code><a
	href="http://nodejs.org/api/child_process.html#child_process.fork">child_process.fork()</a></code>
	these other processes will be scheduled in parallel. For load
	balancing incoming connections across multiple processes use
	<a href="http://nodejs.org/api/cluster.html">the
	cluster module</a>.</p>

	<p>See also:</p>
	<ul>
	<li><a href="http://s3.amazonaws.com/four.livejournal/20091117/jsconf.pdf">Slides from JSConf 2009</a></li>
	<li><a href="http://nodejs.org/jsconf2010.pdf">Slides from JSConf 2010</a></li>
	<li><a href="http://www.yuiblog.com/blog/2010/05/20/video-dahl/">Video from a talk at Yahoo in May 2010</a></li>
	</ul>
	</div>
	</div>
	<div id="footer">
	<a href="http://joyent.com" class="joyent-logo">Joyent</a>
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