1. j@n-dillmann.de
25. Mai 2011
Design and Construction of Distributed Enterprise Applications
TU Darmstadt, SS 2011

2. What?
”Node's goal is to provide an easy way
to build scalable network programs.“
—nodejs.org
2

3. How?
Keeping slow
operations from
blocking other
operations.
3

4. Traditional I/O
var results = db.query("SELECT * FROM TABLE");
// zzzzZZZzzzzz
for (var i=0; i<results.length; i++) {
// process query result
}
// do something else
4

5. Asynchronous I/O
db.query("SELECT * FROM TABLE", function(results) {
for (var i=0; i<results.length; i++) {
// process query result
}
});
// do something else immediately
5

6. And how many threads?
ONLY ONE THREAD?!
threading ain't free
easy to code
no deadlocks
no race-conditions
6

7. var http = require('http');
e. js
ttpsqlit
var sqlite3 = require('sqlite3'); $ node h
var db = new sqlite3.Database('sample.db');
http.createServer(function(request, response) {
response.writeHead(200, {"Content-Type": "text/plain"});
db.all("SELECT * FROM names", function (err, rows) {
rows.forEach(function(row) {
response.write(row.name + ' ' + row.surname + ' (' + row.email + ')n');
});
response.end();
});
}).listen(8000);
console.log("Running at http://127.0.0.1:8000/");
7

8. But how does it work?
client node http sqlite db
create server
console.log listen on 8000
request
SELECT * FROM ...
execute query
get rows
write response
response
8

9. In other words:
”With an event
loop, you ask it to
do something and
it'll get back to you
when it's done.“
—@davidpadbury
9

10. So … what is in there?
com
piles
Java
ide Scri
rS t pt t
rve rip Ass o
Se Sc embl
er
J ava
GOOGLE V8
ted
op even
Lo I/O
Ev ent file
LIBEV LIBEIO
… and more
10

11. node.js 101
Server Side JavaScript
Built on Googles V8
Evented, non-blocking I/O
Single threaded
Everything is asynchronous
Modules for (nearly) everything
Currently only for unix-based systems available *
* on Windows, you can try cygwin, but that is like asking for trouble... 11

12. Where to go next?
http://nodejs.org
http://howtonode.org
http://chaosradio.ccc.de/cre167.html
http://groups.google.com/group/nodejs
http://github.com/joyent/node/wiki/modules
12