explained

Jeff Kunkle

March 2, 2012

Node.js is a platform built on Chrome’s JavaScript runtime for easily building fast, scalable networkapplications. Node.js uses an event driven, non-blocking I/O model that makes it lightweight and

efficient, perfect for data-intensive real-time applications that run across distributed devices.

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v0.6.11

Theory

Benefits

Challenges

123

Theory

I/O LatencyL1 3 cycles

L2 14 cycles

RAM 250 cycles

Disk 41,000,000

Network 240,000,000Source: Ryan Dahl’s 2008.11.08 node.js presentation

0

75,000,000

150,000,000

225,000,000

300,000,000

L1 L2 RAM Disk Network

240,000,000

41,000,000

250143

CPU Cycles

I/O Latency

L2 RAM Disk Network

L1 5 83 13,666,666 80,000,000

L2 18 2,928,571 17,142,857

RAM 164,000 960,000

Disk 6

Waiting...route

request

query db orweb service

processresults

formatresponse

write tolog file

Scaling with Threads

thread 1

thread 2

thread 3

thread 4

Context switching overheadExecution stacks take up memoryComplicates concurrency

Handles up to 4 concurrent requests

Scaling with Processes

process 1

process 2

process 3

process 4

High memory usage

Handles up to 4 concurrent requests

Process scheduling overhead

Scaling with an Event Loop

process 1

network filesystem

Thread Pool and Async I/O APIs

Handles many concurrent requests in one process/thread

Event Loop

filesystem

network

process

other

EventQueue

Thread Pool

EventLoop

Platformnode standard library

node bindings(http, socket, file system)

V8 thread pool(libeio)

event loop(libev)

DNS(c-ares)

crypto(OpenSSL)

Examples

setTimeout(function () { console.log('This will still run.');}, 500);

HTTP Servervar http = require('http');

http.createServer(function (request, response) { response.writeHead(200, {'Content-Type': 'text/plain'}); response.end('Hello World\n');}).listen(8124);

console.log('Server running at http://127.0.0.1:8124/');

Serve a Static Filevar http = require('http');http.createServer(function (request, response) { fs.readFile('/etc/passwd', function (err, data) { if (err) { response.writeHead(500, err.message); response.end(); } else { response.writeHead(200, {'Content-Type': 'text/plain'}); response.end(data); } });}).listen(8124);

Read a File in Chunksvar fs = require('fs');

var stream = fs.createReadStream('huge.txt');stream.on('data', function (data) { console.log(data);});stream.on('end', function () { console.log('done');});stream.on('error', function (err) { console.log(err);});

Challenges

Asynchronous I/Ovar fs = require('fs');

fs.stat('/etc/passwd', function (err, stats) { if (err) return; if (stats.isFile()) { fs.readFile('/etc/passwd', function (err, data) { if (err) throw err; console.log(data); }); }});

Debugging

CPU-intensive Tasks

1thread

be careful!

Rapidly Changing

v0.6.11 2012.02.17

v0.7.5 2012.02.23

v0.7.4 2012.02.14

v0.7.3 2012.02.07

v0.7.2 2012.02.01

v0.7.1 2012.01.23

v0.7.0 2012.01.16

v0.6.10 2012.02.02

v0.6.9 2012.01.27

v0.6.8 2012.01.19

v0.6.7 2012.01.06

v0.6.12 2012.03.02

Benefits

Multi-platform

Lightweight

Single thread

Dead-lock Free

Single thread simplifies concurrency

Monoglot Programming

JavaScript on the client

JavaScript on the server

Popular

Fast Ruby 1.9 used what fraction? times more? Ruby 1.9 used what fraction? times more? Ruby 1.9 used what fraction? times more? Ruby 1.9 used what fraction? times more?

Benchmark Time Memory Code pidigits 1/16 1/2 1/3

reverse-complement 1/2 1/2 1/2

k-nucleotide 2× 1/2 ± binary-trees 6× 1/2 ± fasta 7× 6× ± regex-dna 9× 2× ± n-body 16× 1/4 ± spectral-norm 19× 1/2 ± fannkuch-redux 51× ± ±

Source: http://shootout.alioth.debian.org/u32/benchmark.php

Lua

Perl

PHP

Python 3

JRuby

Clojure

Java

C

Vibrant Community

7,661 packagesas of 3:00pm EDT 2012.03.02

Conceptually Simple

filesystem

network

process

other

EventQueue

Thread Pool

EventLoop

Small Core

36 JavaScript source files

36 C++ source files

as of March 1, 2012 at 10:50pm on v0.6 branch

Short Learning Curve

Understand JavaScript

Understand Event-based Programming

You just need to learn new APIs

Understand Node.js Theory

Getting Smart

1 install Node from source

2 write some small programs

3 read the source

4 re-implement a popular pkg

Check out some Packages

expressweb framework

persistORM framework

db-migratedatabase migrations

asyncasync helpers

socket.iorealtime networking

dnodeRPC

vowsBDD framework

javabridge to Java API