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<html>
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<style>
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body {
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background: #22252a;
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color: #eee;
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font-size: 16pt;
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line-height: 150%;
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font-family: times, Times New Roman, times-roman, georgia, serif;
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}
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#content {
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max-width: 30em;
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margin: 0 0 5em 10em;
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}
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#toc {
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position: fixed;
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top: 2em;
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left: 0;
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width: 10em;
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}
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#toc ol {
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#toc ol li {
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margin: 0;
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padding: 0;
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}
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#toc a { color: #777; }
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h1, h2, h3 { color: inherit; }
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h1 {
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margin: 2em 0;
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}
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h1 a { color: inherit; }
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h2 {
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margin: 2em 0;
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h3 {
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margin: 1em 0;
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}
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pre, code {
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font-family: monospace;
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font-size: 14pt;
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}
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a { color: #cd5; text-decoration: none; }
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a:hover { text-decoration: underline; }
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</style>
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<title>node.js</title>
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<body>
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<div id="toc">
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<ol>
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<li><a href="#motivation">Motivation</a></li>
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<li><a href="#benchmarks">Benchmarks</a></li>
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<li><a href="#download">Download</a></li>
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<li><a href="#install">Build</a></li>
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<li><a href="#api">API</a>
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<ol>
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<li><a href="#timers">Timers</a>
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<li><a href="#files">File System</a>
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<li><a href="#tcp">TCP</a>
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<li><a href="#http">HTTP</a>
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<li><a href="#modules">Modules</a>
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</ol>
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</li>
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</ol>
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</div>
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<div id="content">
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<h1><a href="http://tinyclouds.org/node">Node</a></h1>
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<p id="introduction"> Node is a purely evented I/O framework for <a
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href="#">V8 javascript</a>. It enables easy development of
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highly concurrent, efficent network programs. For example, this is a
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simple web server which responds with "Hello World" after waiting two
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seconds:
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<pre class="sh_javascript">
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node.http.server(function (msg) {
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setTimeout(function () {
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msg.sendHeader(200, [["Content-Type", "text/plain"]]);
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msg.sendBody("Hello World");
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msg.finish();
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}, 2000);
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}).listen(8000, "localhost");
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</pre>
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<p> While one request is waiting the server will continue to accept and
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serve other requests. This little server can handle hundreds of
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concurrent requests while using little CPU or memory—<a
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href="#benchmarks">see benchmarks</a>. The example demonstrates
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efficency that is needed for handling long held "comet" requests.
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<p> Node is free to <a href="#download">download</a>, <a
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href="#api">use</a>, and <a href="#modules">build upon</a>.</p>
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<h2 id="motivation">Motivation</h2>
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<ol>
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<li>Evented programming makes sense
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<ol>
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<li>difference between blocking/non-blocking design
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<li>latency figures
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<li>purely evented interfaces rule out a lot of stupidity
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</ol>
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<li>Evented programs are more efficient
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<ol>
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<li>pthread stack size
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2mb default stack size on linux (1mb on windows, 64kb on FreeBSD)
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of course this is adjustable
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<li>context switching benchmark
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<li>Apache vs. Nginx
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<li>event machine vs mongrel (neverblock)
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</ol>
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<li>The appropriateness of Javascript
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<ol>
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<li>No I/O
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<li>No Threads
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<li>Good compiler
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<li>Universality of the language
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</ol>
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</ol>
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Threads are a bad model.
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<p>
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<a href="http://duartes.org/gustavo/blog/post/what-your-computer-does-while-you-wait">I/O latency</a>
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<pre>
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l1 cache ~ 3
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l2 cache ~ 14
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ram ~ 250
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disk ~ 41000000
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network ~ 240000000
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</pre>
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<p> Javascript is without I/O. In the browser the DOM provides I/O,
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but non-browser javascript interpreters have only non-standardized
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functions to allow them print to console or access the network.
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<p> Javascript is without the concept of threads.
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<p> Contemporary computer infrastructure has two irreplaceable
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languages: C and Javascript. C is the language of operating systems.
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POSIX, the universal operating system API, is defined in C. So while you
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can interface with operating systems in Java and Haskell, those
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languages access must make system calls in C. Similarly, Javascript is
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the language of the web operating system. In place of POSIX is the
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DOM. You can wrap Javascript, you can compile to Javascript, but in the
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end browsers must be interfaced with in Javascript. Portable low-level
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systems tend to be written in C and portable web-level systems are
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written in Javascript.
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<h3>Evented vs Threaded Servers</h3>
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<p> There are many methods to write internet servers but they can
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fundamentally be divided into two camps: evented and threaded; non-blocking
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and blocking. A blocking server accepts a connection and launches a new
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thread to handle the connection. Because the concurrency is handled by
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the thread scheduler, a blocking server can make function calls which
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preform full network requests.
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<pre class="sh_javascript">var response = db.execute("SELECT * FROM table");
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// do something</pre>
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<p> An evented server manages its concurrency itself. All connections
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are handled in a single thread and callbacks are executed on certain
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events: "socket 23 is has data to read", "socket 65's write buffer is
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empty". An evented server executes small bits of code but never
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<i>blocks</i> the process. In the evented world callbacks are used
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instead of functions
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<pre class="sh_javascript">db.execute("SELECT * FROM table", function (response) {
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// do something
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});</pre>
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<h2 id="benchmarks">Benchmarks</h2>
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<h2 id="download">Download</h2>
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<h2 id="build">Build</h2>
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<pre>configure
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make
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make install</pre>
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<h2 id="api">Application Programming Interface</h2>
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<p> The node executable should be given an argument pointing to a
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javascript file.
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<h3 id="timers">Timers</h3>
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<p>The timer API is the same as in the browser. The functions
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<code>setTimeout, setInterval, cancleTimeout, and cancleInterval</code>
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<h3 id="files">File System</h3>
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<h3 id="tcp">TCP</h3>
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<h3 id="http">HTTP</h3>
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<h3 id="modules">Modules</h3>
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</body>
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</html>
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