node-0.1.1.tar.gz

NODE(1) ======= Ryan Dahl <ry@tinyclouds.org> Version, 0.1.1, 2009.07.27 == NAME node - purely event-based I/O for V8 javascript == SYNOPSIS An example of a web server written with Node which responds with "Hello World" after waiting two seconds: ---------------------------------------- node.http.createServer(function (request, response) { setTimeout(function () { response.sendHeader(200, [["Content-Type", "text/plain"]]); response.sendBody("Hello World"); response.finish(); }, 2000); }).listen(8000); puts("Server running at http://127.0.0.1:8000/"); ---------------------------------------- To run the server, put the code into a file called +example.js+ and execute it with the node program ---------------------------------------- > node example.js Server running at http://127.0.0.1:8000/ ---------------------------------------- == DESCRIPTION Node provides an easy way to build scalable network programs. In the above example, the 2 second delay does not prevent the server from handling new requests. Node tells the operating system (through +epoll+, +kqueue+, +/dev/poll+, or +select+) that it should be notified when the 2 seconds are up or if a new connection is made--then it goes to sleep. If someone new connects, then it executes the callback, if the timeout expires, it executes the inner callback. Each connection is only a small heap allocation. This is in contrast to today's more common model where OS threads are employed for concurrency. Thread-based networking http://www.sics.se/~joe/apachevsyaws.html[is] http://www.kegel.com/c10k.html[relatively] http://bulk.fefe.de/scalable-networking.pdf[inefficient] and very difficult to use. 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. In fact, no function in Node directly performs I/O. Because nothing blocks, less-than-expert programmers are able to develop fast systems. Node is similar in design to systems like Ruby's http://rubyeventmachine.com/[Event Machine] or Python's http://twistedmatrix.com/[Twisted]. Node takes the event model a bit further. For example, 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 call like +EventMachine::run()+. In Node it works differently. By default Node enters the event loop after executing the input script. Node exits the event loop when there are no more callbacks to perform. Like in traditional browser javascript, the event loop is hidden from the user. Node's HTTP API has grown out of my difficulties developing and working with web servers. For example, streaming data through most web frameworks is impossible. Or the oft-made false assumption that all message headers have unique fields. Node attempts to correct these and other problems in its API. Coupled with Node's purely evented infrastructure, it will make a more comprehensive foundation for future web libraries/frameworks. _But what about multiple-processor concurrency? Threads are necessary to scale programs to multi-core computers._ The name _Node_ should give some hint at how it is envisioned being used. Processes are necessary to scale to multi-core computers, not memory-sharing threads. The fundamentals of scalable systems are fast networking and non-blocking design--the rest is message passing. In the future, I'd like Node to be able to spawn new processes (probably using the http://www.whatwg.org/specs/web-workers/current-work/[Web Workers API]), but this is something that fits well into the current design. == API Node supports 3 byte-string encodings: ASCII (+"ascii"+), UTF-8 (+"utf8"+), and raw binary (+"raw"+). It uses strings to represent ASCII and UTF-8 encoded data. For the moment, arrays of integers are used to represent raw binary data--this representation is rather inefficient. This will change in the future, when http://code.google.com/p/v8/issues/detail?id=270[V8 supports Blob objects]. Unless otherwise noted, functions are all asynchronous and do not block execution. === Helpers +puts(string)+:: Alias for +stdout.puts()+. Outputs the +string+ and a trailing new-line to +stdout+. + Everything in node is asynchronous; +puts()+ is no exception. This might seem ridiculous but, if for example, one is piping +stdout+ into an NFS file, +printf()+ will block from network latency. There is an internal queue for +puts()+ output, so you can be assured that output will be displayed in the order it was called. +node.debug(string)+:: A synchronous output function. Will block the process and output the string immediately to stdout. +p(object)+ :: Print the JSON representation of +object+ to the standard output. +print(string)+:: Like +puts()+ but without the trailing new-line. +node.exit(code)+:: Immediately ends the process with the specified code. === Global Variables +ARGV+ :: An array containing the command line arguments. +stdout+, +stderr+, and +stdin+ :: Objects of type +node.fs.File+. (See below.) +__filename+ :: The filename of the script being executed. === Events Many objects in Node emit events: a TCP server emits an event each time there is a connection, a child process emits an event when it exits. All objects which emit events are are instances of +node.EventEmitter+. Events are represented by a snakecased string. Here are some examples: +"connection"+, +"receive"+, +"message_begin"+. Functions can be then be attached to objects, to be executed when an event is emitted. These functions are called _listeners_. Some asynchronous file operations return an +EventEmitter+ called a _promise_. A promise emits just a single event when the operation is complete. ==== +node.EventEmitter+ +emitter.addListener(event, listener)+ :: Adds a listener to the end of the listeners array for the specified event. + ---------------------------------------- server.addListener("connection", function (socket) { puts("someone connected!"); }); ---------------------------------------- +emitter.listeners(event)+ :: Returns an array of listeners for the specified event. This array can be manipulated, e.g. to remove listeners. +emitter.emit(event, args)+ :: Execute each of the listeners in order with the array +args+ as arguments. ==== +node.Promise+ +node.Promise+ inherits from +node.eventEmitter+. A promise emits one of two events: +"success"+ or +"error"+. After emitting its event, it will not emit anymore events. +promise.addCallback(listener)+ :: Adds a listener for the +"success"+ event. Returns the same promise object. +promise.addErrback(listener)+ :: Adds a listener for the +"error"+ event. Returns the same promise object. === Modules Node has a simple module loading system. In Node, files and modules are in one-to-one correspondence. As an example, +foo.js+ loads the module +circle.js+. The contents of +foo.js+: ---------------------------------------- var circle = require("circle.js"); function onLoad () { puts("The area of a cirlce of radius 4 is " + circle.area(4)); } ---------------------------------------- The contents of +circle.js+: ---------------------------------------- var PI = 3.14; exports.area = function (r) { return PI * r * r; }; exports.circumference = function (r) { return 2 * PI * r; }; ---------------------------------------- The module +circle.js+ has exported the functions +area()+ and +circumference()+. To export an object, add to the special +exports+ object. (Alternatively, one can use +this+ instead of +exports+.) Variables local to the module will be private. In this example the variable +PI+ is private to +circle.js+. The module path is relative to the file calling +require()+. That is, +circle.js+ must be in the same directory as +foo.js+ for +require