Node.js
0 likes451 views
This document discusses Node.js and its approach to handling input/output (I/O) operations in a non-blocking and asynchronous way. It notes that I/O operations like accessing the disk or network can be very slow, taking millions of cycles. Node.js addresses this by using an event-driven, asynchronous programming model where callbacks are used to handle the results of slow I/O operations without blocking the main thread. Examples are given to illustrate how Node.js handles database queries and HTTP requests asynchronously in a non-blocking way to improve performance compared to traditional synchronous approaches or other web servers.
Node.js
- 2. Introduction "Node's goal is to provide an easy way to build scalable network programs." Ryan Dahl ●Server-side Javascript ●Built on Google’s V8 ●CommonJS module system ●Evented, non-blocking I/O. Similar to EventMachine or Twisted.
- 3. I/O needs to be done differently.
- 4. I/O Costs ●L1: 3 cycles ●L2: 14 cycles ●RAM: 250 cycles ●DISK: 41,000,000 cycles ●NETWORK: 240,000,000 cycles http://nodejs.org/jsconf.pdf
- 5. Traditional way var db = require('db'); row = db.query(' SELECT id, name FROM aaa'); row2 = db.query('SELECT id, name WHERE id = '+row.id ); // do your stuff here console.log( row2.name );
- 6. I/O Costs ●L1: 3 cycles ●L2: 14 cycles ●RAM: 250 cycles ●DISK: 41,000,000 cycles ●NETWORK: 240,000,000 cycles http://nodejs.org/jsconf.pdf
- 7. Node's first attempt var db = require('db'); db.query(' SELECT id, name FROM table', function(row){ db.query('SELECT .... WHERE id = '+row.id, function(row2){ // do your stuff here console.log( row2.name ); }); });
- 8. Better way var db = require('db'); frunction get(cb){ db.query('SELECT id, name FROM table', row1); } function row1(row, cb){ db.query('SELECT .... WHERE id = '+ row.id, function(row){ cb( row ); }); } get(function(row){ console.log( row.name ); });
- 9. speed
- 10. speed var http = require(’http’); var b = new Buffer(1024*1024); http.createServer(function(req, res){ res.writeHead(200); res.end(b); }).listen(8000); by Ryan Dahl
- 11. speed 100 concurrent clients 1 megabyte response req/sec node ~800 nginx ~700 thin 85 mongrel 4 (bigger is better) by Ryan Dahl
- 12. Questions?