Rising from non-existence a few short years ago, Node.js is already attracting the accolades and disdain enjoyed and endured by the Ruby and Rails community just a short time ago. It overtook Rails as the most popular Github repository in 2011 and was selected by InfoWorld for the Technology of the Year Award in 2012. This presentation explains the basic theory and programming model central to Node's approach and will help you understand the resulting benefits and challenges it presents. You can also watch this presentation at http://bit.ly/1362UGA

1. explained
March 2, 2012
Jeff Kunkle

2. Node.js is a platform built on Chrome’s JavaScript runtime for easily building fast, scalable network
applications. 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.
DOWNLOAD DOCS
v0.6.11

3. 1 Theory
2 Challenges
3 Benefits

4. Theory

5. I/O Latency
L1 3 cycles
L2 14 cycles
RAM 250 cycles
Disk 41,000,000
Network 240,000,000
Source: Ryan Dahl’s 2008.11.08 node.js presentation

6. CPU Cycles
300,000,000
240,000,000
225,000,000
150,000,000
75,000,000
41,000,000
3 14 250
0
L1 L2 RAM Disk Network

7. 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

8. Waiting...
route process format
request results response
query db or write to
web service log file

9. Scaling with Threads
Handles up to 4 concurrent requests
thread 1
thread 2
thread 3
thread 4
Context switching overhead
Execution stacks take up memory
Complicates concurrency

10. Scaling with Processes
Handles up to 4 concurrent requests
process 1
process 2
process 3
process 4
High memory usage
Process scheduling overhead

11. Scaling with an Event Loop
Handles many concurrent requests in one process/thread
process 1
network filesystem
Thread Pool and Async I/O APIs

12. Event Loop
Thread Pool
Event filesystem
Queue
network
Event
Loop process
other

13. Platform
node standard library
node bindings
(http, socket, file system)
thread pool event loop crypto DNS
V8
(libeio) (libev) (OpenSSL) (c-ares)

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

15. HTTP Server
var http = require('http');
http.createServer(function (request, response) {
response.writeHead(200, {'Content-Type': 'text/plain'});
response.end('Hello Worldn');
}).listen(8124);
console.log('Server running at http://127.0.0.1:8124/');

16. Serve a Static File
var 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);

17. Read a File in Chunks
var 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);
});

18. Challenges

19. Asynchronous I/O
var 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);
});
}
});

20. Debugging

21. CPU-intensive Tasks
1 thread
be careful!

22. Rapidly Changing
v0.6.12 2012.03.02 v0.7.5 2012.02.23
v0.6.11 2012.02.17 v0.7.4 2012.02.14
v0.6.10 2012.02.02 v0.7.3 2012.02.07
v0.6.9 2012.01.27 v0.7.2 2012.02.01
v0.6.8 2012.01.19 v0.7.1 2012.01.23
v0.6.7 2012.01.06 v0.7.0 2012.01.16

23. Benefits

24. Multi-platform

25. Lightweight
Single thread

26. Dead-lock Free
Single thread simplifies concurrency

27. Monoglot Programming
JavaScript on the client
JavaScript on the server

28. Popular

29. Fast 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

30. Lua

31. Perl

32. PHP

33. Python 3

34. JRuby

35. Clojure

36. Java

37. C

38. Vibrant Community
7,661 packages
as of 3:00pm EDT 2012.03.02

39. Conceptually Simple
Thread Pool
Event filesystem
Queue
network
Event
Loop process
other

40. Small Core
36 JavaScript source files
36 C++ source files
as of March 1, 2012 at 10:50pm on v0.6 branch

41. Short Learning Curve
Understand Node.js Theory
Understand JavaScript
Understand Event-based Programming
You just need to learn new APIs

42. Getting Smart

43. 1 install Node from source
2 write some small programs
3 read the source
4 re-implement a popular pkg

44. Check out some Packages
express
web framework
async helpers
async
persist socket.io
realtime networking
ORM framework
db-migrate vowsframework
BDD
database migrations
dnode
RPC
java to Java API
bridge