Beginners Node.js
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Node.js is a server-side JavaScript environment that allows building scalable network applications. It uses Google Chrome's V8 JavaScript engine and runs on a single thread without blocking I/O operations. Node.js is optimized for non-blocking event-driven operations and has a large ecosystem of reusable modules. Some common uses of Node.js include real-time web applications, REST APIs, streaming data applications, and networking servers.
![Lets connect to a DB (MongoDB)
• Install mongojs using npm, a mongoDB driver for
Node.js
npm install mongojs
• Code to retrieve all the documents from a
collection:
var db = require("mongojs")
.connect("localhost:27017/test", ['test']);
db.test.find({}, function(err, posts) {
if( err || !posts) console.log("No posts found");
else posts.forEach( function(post) {
console.log(post);
});
});](https://image.slidesharecdn.com/node-160319124900/85/Beginners-Node-js-19-320.jpg)
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Beginners Node.js
- 1. Server side JavaScript environment Khaled Mosharraf, M.Sc Fh Kiel Germany [email protected] A.K.M Bahalul Haque, M.Sc M.Sc Fh Kiel Germany [email protected]
- 2. What is NodeJS? Complete software platform for scalable server-side & networking applications Bundled with JavaScript Interpreter JavaScript runtime environment running Google Chrome’s V8 engine Runs over command line Never blocks, not even for I/O Uses the CommonJS framework Making it a little closer to a real OO language
- 4. Why is it so cool...... • Node JS is fast, in theory • Low maintenance (small impact on resources) • Programs must not stress the CPU • Programming is not THAT easy • API are well documented • The Node JS standard library can be EXTENDED by the use of modules • the number of available modules is HUGE • optimised (low resources) • runs everywhere
- 5. Overall Structure Two Main Components are -- • Main Core, written in C & C++ • Modules, such as Libuv library and V8 runtime engine, also written in C++
- 6. Background-Achitecture • libev(event loop) • libeio(non-block thread pool) • V8(Javascript engine)
- 7. What can NodeJS be used for….. • Http, • networking, • Websockets • Network servers (HTTP, Proxies, messaging) • API backends • Real time applications • Streaming data “One page” web sites • Command line tools • Bots ---but also it is an invaluable tool for developers
- 8. Browsers • Every browser has its own VM • Firefox? Spidermonkey • Internet Explorer? Chakra • Chrome? V8 • Safari? JavaScriptCore • Opera? Carakan • Also Rhino, stand alone • Completely event driven (asynchronous, non- blocking)
- 9. When to use Node.js? • Node.js is good for creating streaming based real-time services, web chat applications, static file servers etc. • If you need high level concurrency and not worried about CPU-cycles. • If you are great at writing JavaScript code because then you can use the same language at both the places: server-side and client-side.
- 10. When to not use Node.js • When you are doing heavy and CPU intensive calculations on server side, because event-loops are CPU hungry. • Node.js API is still in beta, it keeps on changing a lot from one revision to another and there is a very little backward compatibility. Most of the packages are also unstable. Therefore is not yet production ready. • Node.js is a no match for enterprise level application frameworks like Spring(java), Django(python), Symfony(php) etc. Applications written on such platforms are meant to be highly user interactive and involve complex business logic. • Read further on disadvantages of Node.js on Quora: http://www.quora.com/What-are-the-disadvantages-of-using- Node-js
- 11. Features Non-blocking I/O Event Driven CommonJS
- 13. Async
- 14. Event Loop Example • Request for “index.html” comes in • Stack unwinds and ev_loop goes to sleep • File loads from disk and is sent to the client
- 15. What is the “Node Standard Library”? • A powerful HTTP(S) library (client and server in no time) • DNS name resolution • Crypto • Access to the file system • URL manipulation • ZLIB • UDP datagrams
- 16. Event-loops • Event-loops are the core of event-driven programming, almost all the UI programs use event-loops to track the user event, for example: Clicks, Ajax Requests etc. Client Event loop (main thread) C++ Threadpool (worker threads) Clients send HTTP requests to Node.js server An Event-loop is woken up by OS, passes request and response objects to the thread-pool Long-running jobs run on worker threads Response is sent back to main thread via callback Event loop returns result to client
- 17. Node.js benchmarks Taken from: http://nodejs.org/jsconf2010.pdf The benchmark shows the response time in milli-secs for 4 evented servers. Taken from: http://code.google.com/p/node-js-vs-apache- php-benchmark/wiki/Tests A benchmark between Apache+PHP and node.js, shows the response time for 1000 concurrent connections making 10,000 requests each, for 5 tests.
- 18. Example (HTTP Server & TCP Server) • Following code creates an HTTP Server and prints ‘Hello World’ on the browser: var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello Worldn'); }).listen(5000, "127.0.0.1"); • Here is an example of a simple TCP server which listens on port 6000 and echoes whatever you send it: var net = require('net'); net.createServer(function (socket) { socket.write("Echo serverrn"); socket.pipe(socket); }).listen(6000, "127.0.0.1");
- 19. Lets connect to a DB (MongoDB) • Install mongojs using npm, a mongoDB driver for Node.js npm install mongojs • Code to retrieve all the documents from a collection: var db = require("mongojs") .connect("localhost:27017/test", ['test']); db.test.find({}, function(err, posts) { if( err || !posts) console.log("No posts found"); else posts.forEach( function(post) { console.log(post); }); });
- 20. Node.js Ecosystem • Node.js heavily relies on modules, in previous examples require keyword loaded the http & net modules. • Creating a module is easy, just put your JavaScript code in a separate js file and include it in your code by using keyword require, like: var modulex = require(‘./modulex’); • Libraries in Node.js are called packages and they can be installed by typing npm install “package_name”; //package should be available in npm registry @ nmpjs.org • NPM (Node Package Manager) comes bundled with Node.js installation.
- 21. Critical Analysis...... Benefits • Because of single threaded nonb locking scheme nodejs can support up to one million concurrent nodes • Can be used to implement entire havascript based web applications • Request are acknowledged because of asynchronous nature • Native JSON handling • Easy RESTful services • Speedy native bindings in C • Realtime nature i.e possible to process fiels while they are being uploaded
- 22. Critical Analysis...... Best for.. • REST + JSON Api • Quick Prototyping • Chat applications • Ideal for computing and orchastration tasks • For fast growing applications
- 23. Limitations.... • Tightly coupled Node & V8 engines • Low fault tolerance • Exception handling • Some lackings in code quality
- 24. Who is using Node.js in production? • Yahoo! : iPad App Livestand uses Yahoo! Manhattan framework which is based on Node.js. • LinkedIn : LinkedIn uses a combination of Node.js and MongoDB for its mobile platform. iOS and Android apps are based on it. • eBay : Uses Node.js along with ql.io to help application developers in improving eBay’s end user experience. • Dow Jones : The WSJ Social front-end is written completely in Node.js, using Express.js, and many other modules. • Complete list can be found at: https://github.com/joyent/node/wiki/Projects,- Applications,-and-Companies-Using-Node
- 25. Conclusion Still in beta Non-blocking nature takes some getting used to Interesting API Can almost remake Dash!