Node.js primer

Node.js primer

• 1.
  Node.js That's what happenswhen JavaScript runs on Server too By Swapnil Mishra
• 2.
  But Javascript onserver ?
• 3.
  • Powerful JavaScriptengine which powers Google Chrome browser and Chrome OS. • Can also be considered as a Virtual Machine. • Node.js runs on the top of V8. • Utilizes the networking and parsing features which are done elegantly in V8. V8 made it possible
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  • There aredifferences in the JavaScript which runs in browser vs node.js. e.g. There are no "window" or "document" objects. • Things which have been taken from V8 are asynchronous/non- blocking nature of JavaScript, Syntax, Data Structures(most of them). Which means everyones favorite closure/anonymous functions will work here too. • Things which have been added into it are Timers, Processes, Events, Buffers, Streams, Crypto, File Systems, HTTP, HTTPS and many more. Wait, so you are saying this node.js is same as the javascript which runs in browser ?
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  • Model isevented rather than threaded. • Using an event loop, you ask it to do something and it will get back to you when its done.(we will see an example later) • Conventional languages are run in threaded environment where they create threads and just loop/pool in to wait for the result. Thats not the case with node.js. • Because of the evented nature it can perform Non-Blocking Network I/O. Oh cool tell me more about it !!
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  Example of BlockingI/O public INeedData { public Data getMeSomeData(queryParam){ Data toBeReturned = db.query(queryParam); iAmBlockedTillQueryExecutes(); return toBeReturned; Blocking I/O } } // get data performs blocking I/O call because of which // iAmBlockedTillQueryExecutes() is blocked Why should i care about Non-Blocking I/O ?
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  Think about whatwe really do on web server. • Grab Files • Call Databases • Pull from caches • Wait on other connections It's all I/O and we know that I/O latency of network is highest. Why should i care about Non-Blocking I/O ?
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  • Totally andso does web-servers like Apache, IIS. • But threading is not free. • There are context switches and executions stacks take memory. What should we do then ? Hey but that's exactly why i use thread
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  Use a singlethread. Do little pieces of work and do them quickly. But single thread !!! We have been using multithreading from ages when UI used to be in "Java Swing" !!! Are you crazy ? Can it handle ? Event loop comes to the rescue
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  Apache vs NGINX
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  Apache vs NGINX
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  The difference? • Apacheuses one thread per connection. • NGINX does not use threads. It uses an event loop. So basically we have to change our programming model to something where we could easily write non-blocking code. public INeedData { public Data getMeSomeData(queryParam){ Data toBeReturned = db.query(queryParam,function(){ return toBeReturned;}); iAmNotBlockedTillQueryExecutes(); } } Apache vs NGINX
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  • Node.js isa set of bindings for writing high-performance network servers. • Exposes only non-blocking I/O API's • Stops us writing code that behaves badly. Below is code for a simple http server in Node.js var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello Worldn'); }).listen(1337, '127.0.0.1'); console.log('Server running at http://127.0.0.1:1337/'); Now i got it
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  • Node.js isbeing used by many companies including big names like Linkedin, WalMart in fact Linkedin's mobile backend is totally on node.js. • Excellent package manager npm(Node Package Manager). • Installing packages: npm install <package> • npm can also be used for dependency management just like maven. • One more reason for Node.js's popularity is huge base of javascript developers who can now write backend code too. Production Usage ?
• 15.
  Thank You !!! Timefor a quick demo