NodeJS

Intro to NodeJS
Matthew Eernisse
Toster Conference 2011-10-28

Who am I?
Matthew Eernisse
Work at Yammer
@mde on Twitter

JavaScript at Yammer
• Browsers (yammer.com Web UI)
• Adobe AIR Desktop
• V8 in Rails via TheRubyRacer
• NodeJS

NodeJS:
“Evented I/O for V8 JavaScript”
http://nodejs.org/

Hello, NodeJS
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/');

History of SSJS
• Netscape Enterprise Server (OG SSJS)
• Microsoft IIS
• Helma (now RingoJS)
• Whitebeam
• Zimki
• Jaxer
• Perservere
• Nitro
• Google App Engine
• CouchDB
• NodeJS

Why NodeJS now?
• Steve Yegge’s NBL post, 2007-02-10
• Competition in JavaScript interpreters
• Simple, POSIX API
• Non-blocking from the ground up; so
are the libraries

What is NodeJS good for?
• Lightweight, networked apps
• Proxies with embedded logic
• Streaming data
• System scripting
• Evented realtime apps

NodeJS is not good at complex
database-backed Web
applications.
You can use Rails.

Geddy Web framework:
https://github.com/mde/geddy

NodeJS at Yammer
• Development proxy

• Jake for build and test (https://github.com/mde/jake)

• Upload service for ﬁles and images (Geddy v0.2)

• Browserless tests with FooUnit
(https://github.com/foobarﬁghter/foounit)

• Realtime, collaborative document-editing service

Jake build tool
https://github.com/mde/jake

• Similar to Make or Rake

• Tasks, prerequisites

• File tasks, directory tasks

• Namespaces

• PackageTasks

• Async task execution

• Just executable JavaScript

desc('This is the default task.');
task('default', function () {
console.log('This is the default task.');
console.dir(arguments);
});

namespace('foo', function () {
desc('This the foo:bar task');
task('bar', function () {
console.log('doing foo:bar task');
});

desc('This the foo:baz task');
task('baz', ['default', 'foo:bar'], function () {
console.log('doing foo:baz task');
});

});

desc('This is an asynchronous task.');
task('async', function () {
setTimeout(function () {
console.log('Hooray!');
complete();
}, 1000);
}, true);

desc('Calls the foo:bar task and its dependencies.');
task('invokeFooBar', function () {
// Calls foo:bar and its deps
jake.Task['foo:bar'].invoke();
// Does nothing
// Only re-runs foo:bar, but not its dependencies
jake.Task['foo:bar'].reenable();
});

var fs = require('fs')
, pkg = JSON.parse(
fs.readFileSync('package.json').toString())
, version = pkg.version

var t = new jake.PackageTask('jake', 'v' + version,
function () {
var fileList = [
'Makefile'
, 'Jakefile'
, 'README.md'
, 'package.json'
, 'lib/*'
, 'bin/*'
, 'tests/*'
];
this.packageFiles.include(fileList);
this.needTarGz = true;
this.needTarBz2 = true;
});

Remote upload service
• Minimal v1 in prod, Nov. 2010

• Redis, CORS XHR-push or JSONP for upload-progress
reporting

• Onboard thumbnailing, remote services for video and
document post-processing

• Three-machine cluster, not under a heavy load

• Large ﬁle sizes (e.g., 1.5GB)

Realtime, collaborative
doc-editing service
• In beta Oct. 21, 2011 (last week)

• NodeJS, Socket.io, PostgreSQL

• No production metrics yet for perf/scalability

Awesome:
JavaScript is simple and
super-ﬂexible

Horrible:
JavaScript is simple and
super-ﬂexible

Asynchronous code
• Even shelling out is async?
• “1, 3, 2, go!” development
• Evented and callback-based control-ﬂow
• A familiar model?
• Async patterns and libraries

1, 3, 2, go!
var asyncFun = function () {
console.log('1');
setTimeout(function () {
console.log('3');
}, 0);
console.log('2');
console.log('go!');
};

Sync fetch-and-update
var fetchAndUpdate = function (params) {
var items = db.fetch(someQuery);
for (var i = 0, ii = items.length; i++) {
item.update(params);
}
return true;
};

Async fetch-and-update
var fetchAndUpdate = function (params, callback) {
db.fetch(someQuery, function (items) {
var count = 0;
for (var i = 0, ii = items.length; i++) {
item.update(params, function () {
count++;
if (count == ii) {
callback(true);
}
});
}
});
};

Is this familiar?
jQuery.ajax({
url: '/foo/bar.json'
, success: function () {
alert('yay!');
}
});

jQuery('#foo').bind('click', function (e) {
// Do some stuff
});

Async patterns and libs

• Queue
• Promise/deferred
• In-ﬂight registry

Queue
var asyncQueueHandler = function (items,
handler, callback) {
var queue = items.slice()
, handleNextItem = function () {
var next = queue.pop();
if (next) {
handler(next, function () {
handleNextItem();
});
}
else {
callback();
}
};
handleNextItem();
};

Promise
var p = new yammer.util.Promise();
p.when('foo', 'bar', 'baz').then(
function () {
console.log('done!');
});
p.satisfy('foo');
p.satisfy('bar');
p.satisfy('baz');

p.then(function () {
console.log('still done!');
});

App dependencies

• Third-party modules still may change
rapidly
• Maintain forks, push back patches where
appropriate

Debugging NodeJS
• Callbacks in global scope have no stack
• Assume you’re fucked
• Default condition is a preemptible error
• In-ﬂight registry with uncaughtException
handler

FlightCheck
https://github.com/mde/flight_check

• Add items to in-flight registry

• Per-item timeout

• Configurable polling-interval

• Define a timeout-handler

In-ﬂight registry
var FlightCheck = require('flight_check').FlightCheck;
var handler = function (req, resp) {
var checker = new FlightCheck(function (key) {
resp.writeHead(500);
resp.end('Oops, something bad happened.');
});
checker.add('foo', 10000);
doFoo(req, function (result) {
if (result.ok) {
checker.clear('foo');
// Do some other stuff
resp.writeHead(200);
resp.end('Hooray!');
}
});
};

process.on('uncaughtException', function (err) {
// Do some kind of logging
});

Visibility, metrics

• Measure everything
• Log everything
• https://github.com/mikejihbe/metrics

Ops

• Communicative, consultative dev
• Ask what is expected
• Play nicely with others

The future?
• JS interpreters will keep improving
• JS language will keep improving (see:
JS.next)
• NodeJS ecosystem will grow and mature
• Try NodeJS, you’ll like it

Matthew Eernisse
http://twitter.com/mde

Yammer Developer Center
http://developer.yammer.com/

NodeJS

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Editor's Notes