Async. and Realtime Geo Applications with Node.js

Async & RT Geo
apps with Node.js
Kashif Rasul @krasul
Shoaib Burq @sabman

http://spacialdb.com
(@SpacialDB)

Checkout tomorrow
• Techniques for distributed high-speed map
tile generation using Mapnik & Node.js by
Simon & Javier @ 13:00 Silver Room
• The State of GeoCouch by Volker @ 15:00
Silver Room
• The new GeoData tool set: CouchDB and
NodeJS by Mick @ 15:30 Silver Room

By the end of this you
will know...
• what Node.js is.
• how to write and deploy Node.js servers.
• a bit about coffeescript.
• about the Geostack for Node.js.
• see how to write and deploy a RT geo app.

Build something useless
but cool :-)

By the end of this..

Node.js

• Event based server side JavaScript based on
Google’s V8 Engine
• Event based: good at handling a high
number of concurrent connections
• Trick: make network I/O non-blocking and
make most ﬁle I/O asynchronous

Blocking vs. non-
blocking
var result = db.query("select...");

// use result
...

db.query("select..", function (result) {
// use result
...
});

Non-blocking
• Allows the app to return to the event loop
immediately
• But why isn’t everyone using event loops?
• Require I/O to be non-blocking
• Most libs are blocking
• POSIX async I/O not available
• db bindings have no support for async queries
• async DNS resolution not standard etc.

I/O is expensive
• L1 cache 0.5 ns
• Mutex lock/unlock 25 ns
• Main mem. ref. 100 ns
• Send 2K bytes over 1Gbps 20,000 ns
• Read 1MB seq. from mem. 250,000 ns
• Disk seek 10,000,000 ns
• Read 1MB seq. from disk 20,000,000 ns

Rough calc.

• Read 30 images serially each 256K:
• 30 seek × 10 ms/seek + 30 × 256K ÷
30MB/s = 560 ms
• Read them in parallel:
• 10 ms/seek + 256K ÷ 30MB/s = 18 ms

Speed is important

• Amazon: 100ms extra causes 1% drop in
sales
• Google: 500ms extra causes 20% fewer
searches
• Yahoo: 400ms extra causes 5-9% more
“Back” button clicks

Node.js: components

• V8
• libuv: networking layer for all platforms
contains libev, libeio and c-ares
• http_parser: parser for HTTP messages
• openssl

Node.js design

• JS designed to be used with an event loop
• Provide a purely evented non-blocking
infrastructure to script highly concurrent
servers
• No direct I/O: there must be a callback

Node.js: goals
• Low-level API
• Stream everything
• Built-in support for important protocols
like TCP, DNS, HTTP
• Support HTTP features like Chuncked
requests, Keep-alive, Hang requests etc.

HelloWorld.js
by kashif (@krasul)

Node.js: install (Linux)
➜ wget http://nodejs.org/dist/node-v0.4.11.tar.gz
--2011-09-01 15:38:07-- http://nodejs.org/dist/node-v0.4.11.tar.gz
Resolving nodejs.org... 8.12.44.238
Connecting to nodejs.org|8.12.44.238|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 12419274 (12M) [application/octet-stream]
Saving to: `node-v0.4.11.tar.gz'

100%[======================================>] 12,419,274 357K/s in 37s

2011-09-01 15:38:45 (332 KB/s) - `node-v0.4.11.tar.gz' saved [12419274/12419274]

➜ tar xzf node-v0.4.11.tar.gz
➜ cd node-v0.4.11
➜ ./configure
...
➜ sudo make install
...
➜ node -v
v0.4.11

Node.js: install (OS X)
➜ /usr/bin/ruby -e "$(curl -fsSL https://raw.github.com/gist/323731)"
...
➜ brew install node
...
➜ node -v
v0.4.11

➜ sudo port selfupdate
...
➜ sudo port install nodejs
...
➜ node -v
v0.4.11

Node.js: install (Win)

• Grab the installer from http://nodejs.org/
dist/v0.5.5/node.exe
• Unstable version
• Can be built from source by using Cygwin
but it’s a pain in the ass

➜ cat hello.js
var http = require('http');
var net = require('net');
var c = 0;

http.createServer(function(req, res) {
c++;
res.writeHead(200);
res.end('hello worldn');
}).listen(8000);

net.createServer(function(socket) {
socket.write('connections: ' + c);
socket.end();
}).listen(8001);

➜ node hello.js &
[1] 1879

➜ curl -i http://localhost:8000/
HTTP/1.1 200 OK
Connection: keep-alive
Transfer-Encoding: chunked

hello world

Node.js: Modules

• File
• Streams
• Crypto
• HTTP
• DNS

Node Package Manager
➜ curl http://npmjs.org/install.sh | sh
...
npm@1.0.27 /usr/local/lib/node_modules/npm
It worked

➜ npm -v
1.0.27

➜ npm -g install coffee-script
/usr/local/bin/coffee -> /usr/local/lib/node_modules/coffee-script/bin/coffee
/usr/local/bin/cake -> /usr/local/lib/node_modules/coffee-script/bin/cake
coffee-script@1.1.2 /usr/local/lib/node_modules/coffee-script

➜ export NODE_PATH=/usr/local/lib/node_modules

➜ cat package.json
{ "name": "pow"
, "description": "Zero-configuration Rack server for Mac OS X"
, "version": "0.3.2"
, "author": "Sam Stephenson"
, "repository":
{ "type": "git"
, "url": "http://github.com/sstephenson/pow.git"
}
, "bin": { "pow": "./bin/pow" }
, "main": "./lib/index.js"
, "dependencies": {
"async": "0.1.8"
, "coffee-script": ">= 1.1.0"
, "connect": ">= 1.0.3"
, "http-proxy": ">= 0.5.8"
, "log": ">= 1.1.1"
, "nack": ">= 0.12.2"
, "ndns": ">= 0.1.2"
}
, "bundleDependencies" : [ "ndns" ]
, "devDependencies": {
"eco": "= 1.0.3"
, "nodeunit": ">= 0.5.0"
}
, "engines" : { "node" : ">=0.4.1" }
, "scripts": {
"install": "[[ -z "$BUNDLE_ONLY" ]] && cake install || true"
, "test": "cake test"
, "start": "cake start"
, "stop": "cake stop"
}
}

➜ npm install

> pow@0.3.2 install /Users/kashif/node/pow
> [[ -z "$BUNDLE_ONLY" ]] && cake install || true

*** Installing local configuration files...
*** Installed
http-proxy@0.6.6 ./node_modules/http-proxy
├── colors@0.5.0
├── pkginfo@0.2.2
└── optimist@0.2.6

CoffeeScript Quickie!

by shoaib
(@sabman)

CoffeeScript a quick
intro
• Compiles *.coffee down to JavaScript *.js
• Adds to the good parts of JS and gives
familiarity, safety and readability
• Usually need shorter code to generate the
JS you need.

music_style = "Indian"
ask = "Do you like #{music_style} music?"

var ask, music_style;
music_style = "Indian";
ask = "Do you like " + music_style + " music?";

# hashes (json objects) & arrays
ragas =
bhupali:
aaroha: [ 'sa', 're','ga', 'pa', 'dha' ]
avaroha: [ 'dha', 'pa','ga', 're', 'sa' ]
durga:
aaroha: [ 'sa', 're','ma', 'pa', 'dha', 'sa' ]
avaroha: [ 'sa', 'dha', 'pa', 'ma', 're', 'sa']

var ragas;
ragas = {
bhupali: {
aaroha: ['sa', 're', 'ga', 'pa', 'dha'],
avaroha: ['dha', 'pa', 'ga', 're', 'sa']
},
durga: {
aaroha: ['sa', 're', 'ma', 'pa', 'dha', 'sa'],
avaroha: ['sa', 'dha', 'pa', 'ma', 're', 'sa']
}
};

# functions
play = (raga) ->
console.log(ragas[raga]['aaroha'])
console.log(ragas[raga]['avaroha'])
null

play('bhupali')

var play;
play = function(raga) {
console.log(ragas[raga]['aaroha']);
console.log(ragas[raga]['avaroha']);
return null;
};
play('bhupali');

# Classes
class Event
constructor: (@name, @time, @address, @lat, @lon) ->

var Event;
Event = (function() {
function Event(name, time, address, lat, lon) {
this.name = name;
this.time = time;
this.address = address;
this.lat = lat;
this.lon = lon;
}
return Event;
})();

class Event

class Party extends Event
@celeberation: true
@kind: null
hasBalloons: ->
@kind == "Birthday" ? true : false

Event is the name
of the class and
class Event
constructor

class Party extends Event
@celeberation: true
@kind: null
hasBalloons: ->

Event is the name
of the class and
class Event
constructor

Inheritance via class Party extends Event
extends @celeberation: true
@kind: null
hasBalloons: ->

Event is the name
of the class and
class Event
constructor

Inheritance via class Party extends Event
extends @celeberation: true
@kind: null
hasBalloons: ->
Inheritance via
extends @kind == "Birthday" ? true : false

@ deﬁnes an instance
variable

var Event, Party;
var __hasProp = Object.prototype.hasOwnProperty, __extends = function(child, parent) {
for (var key in parent) { if (__hasProp.call(parent, key)) child[key] = parent[key]; }
function ctor() { this.constructor = child; }
ctor.prototype = parent.prototype;
child.prototype = new ctor;
child.__super__ = parent.prototype;
return child;
};
Event = (function() {
function Event(name, time, address, lat, lon) {
this.name = name;
this.time = time;
this.address = address;
this.lat = lat;
this.lon = lon;
}
return Event;
})();
Party = (function() {
__extends(Party, Event);
function Party() {
Party.__super__.constructor.apply(this, arguments);
}
Party.celeberation = true;
Party.kind = null;
Party.prototype.hasBalloons = function() {
var _ref;
return (_ref = this.kind === "Birthday") != null ? _ref : {
"true": false
};
};
return Party;
})();

try it out

event = new Party("Yo! The big party!",
"Thu, 09/15/2011 6:30pm",
"Hamilton Building, Denver Art Museum")

console.log(event.hasBalloons())
# false

event.kind = "Birthday"

console.log(event.hasBalloons())
# true

http://screencasts.org/episodes/introduction-to-coffeescript

Node web
development
(Geo)stack

by kashif
(@krasul)

ﬂickr:darwinbell (cc)

Node.js: Web
Frameworks

• Express: Sinatra inspired and built on
Connect a middleware layer for Node.js
• SocketStream: a fast Real-time web
framework

Express
➜ npm install -g express
/usr/local/bin/express -> /usr/local/lib/node_modules/express/bin/express
express@2.4.6 /usr/local/lib/node_modules/express
├── mime@1.2.2
├── qs@0.3.1
└── connect@1.7.0

➜ cat hello.coffee
express = require('express')
app = express.createServer()
app.set('view engine', 'jade')

# App Routes
app.get '/', (request, response) ->
response.send 'hello world'

# Listen
app.listen 3000
console.log "Express server listening on port %d", app.address().port

Jade

• HTML5 template engine based on HAML
• Supports Express out of the box
• Has ﬁlters for coffee-script

<!DOCTYPE html>
!!! 5 <html lang="en">
html(lang="en") <head>
head <title>Jade</title>
title= pageTitle <script type="text/javascript">
script(type='text/javascript') if (foo) {
if (foo) { bar()
bar() }
} </script>
body </head>
h1 Jade - node template engine <body>
#container <h1>Jade - node template engine</h1>
- if (youAreUsingJade) <div id="container">
p You are amazing <p>You are amazing</p>
- else </div>
p Get on it! </body>
</html>

Database connection

• PostgreSQL + PostGIS via node-pg
• Sqlite3 + Spatialite via node-sqlite3
• CouchDB + GeoCouch via cradle
• SpacialDB via HTTP Client libraries

PostGIS
...
"dependencies": {
...
"pg": "0.5.4"
}

➜ cat server.coffee
...
pg = require "pg"

DATABASE_URL = "pg://postgres:testing@localhost/your_db"

pg.connect DATABASE_URL, (err, client) ->
query = client.query "SELECT * FROM your_table"

query.on 'row', (row) ->
console.log(JSON.stringify(row))
...

Spatialite
...
"dependencies": {
...
"sqlite3": "2.0.16"
}

...
fs = require "fs"
sqlite3 = require "sqlite3"

spatialite_ext = "/usr/local/lib/libspatialite.dylib"

db = new sqlite3.Database "test.sqlite3"

db.loadExtension spatialite_ext, (err) ->
if err throw err

db.each "SELECT...", (err, row) ->
console.log row.id + ": " + row.info

Geocouch
...
"dependencies": {
...
"cradle": "0.5.5"
}

...
cradle = require "cradle"

db = new(cradle.Connection)().database('starwars')

db.get "vader", (err, doc) ->
console.log doc.name
...

Redis
...
"dependencies": {
...
"redis": "0.6.7"
,"hiredis": "0.1.12"
}

...
redis = require("redis")
client = redis.createClient

client.on "error", (err) ->
console.log("Error " + err);

client.set "string key","string val" ->
redis.print

MongoDB
• v2.0 just out with support for multi-location
objects and polygon within searches
• v1.4+ added support for 2d geo point indexes
to do ﬁnd near queries.
• can query for points within a bounding box
• v1.7+ added spherical distance query
• use mongoose a MongoDB object tool for
node.js

Geo bindings

• Geocoder
• Geos/Proj4
• Mapnik

Geocoder

...
"dependencies": {
...
"geocoder": "0.0.5"
}

...
geocoder = require("geocoder")

geocoder.geocode "Denver, CO", (err, data) ->
# do something with the data

node-geos

➜ cat geos.coffee
geonode = require 'geos'

geom = new geonode.Geometry()
geom.fromWkt("POINT(0 0)")

console.log(geom.toWkt())

➜ coffee geos.coffee
POINT (0.0000000000000000 0.0000000000000000)

node-mapnik

• Techniques for distributed high-speed map
tile generation using Mapnik & Node.js by
Simon & Javier. Thursday @ 13:00 Silver
Room

HTTP Client
• github.com/coolaj86/abstract-http-request:
Higher level wrapper around the HTTP
request system
• github.com/danwrong/restler, github.com/
maxpert/Reston & github.com/pﬂeidi/node-
wwwdude: REST client libraries
• github.com/cloudhead/http-console: A
useful interactive shell for HTTP requests

by shoaib
(@sabman)

Building “Chat on a Map”

Starting a node project
package.json
{
"name": "example_2",
"version": "0.0.0",
"dependencies": {
"socket.io" : "*",
"coffee-script": "*",
"request" : "*",
"underscore": "*"
}
}

package.json
{
minimum "version": "0.0.0",
required "dependencies": {
"socket.io" : "*",
"request" : "*",
"underscore": "*"
}
}

package.json
{
"version": "0.0.0",
"dependencies": {
"socket.io" : "*",
"request" : "*",
"underscore": "*"
}
}

$ npm install

server.coffee
Lets write the GeoChat server

fs = require 'fs' # to read static files
http = require 'http' # http server
request = require 'request'
_ = require 'underscore'

server = http.createServer (req, res) ->
fs.readFile "#{__dirname}/map.html", (err, data) ->
res.writeHead 200, 'Content-Type': 'text/html'
res.end data, 'utf8'

server.listen(process.env.PORT || 3000)

io = require('socket.io').listen server
io.sockets.on 'connection', (socket) ->
clientId = socket.id

socket.on 'disconnect', (message) ->
# find the client & delete it ...

socket.on 'publish', (message) ->
# ...

socket.on 'broadcast', (message) ->
# find the client and broadcast their message
socket.broadcast.send(chat_data)
# forwards message to all the clients except the one
# that emitted the "broadcast" event

socket.on 'addUser', (message) ->
# create a new user and broadcast their existance
socket.broadcast.emit 'newUser', new_record

imports

fs.readFile "#{__dirname}/map.html", (err, data) ->
res.writeHead 200, 'Content-Type': 'text/html'




# ...


# create a new user and broadcast their existence

imports

fs.readFile "#{__dirname}/map.html", (err, data) -> serve static http via
res.writeHead 200, 'Content-Type': 'text/html' node




# ...



imports


server.listen(process.env.PORT || 3000) listening port


# ...



imports


io = require('socket.io').listen server bind socket & store
session


# ...



imports


session

disconnect event
# find the client & delete it ... delete the user
# ...



imports


session

disconnect event
# ... broadcast: verify the
client and broadcast
# find the client and broadcast their message the message with
socket.broadcast.send(chat_data) user details


imports


session

disconnect event
# ... broadcast: verify the
client and broadcast
# find the client and broadcast their message the message with
socket.broadcast.send(chat_data) user details

socket.on 'addUser', (message) -> respond to ‘addUser’
# create a new user and broadcast their existence custom event & emit
‘newUser’ custom

client code
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8">
<title>GeoChat :: FOSS4G-2011</title>
<script src="/socket.io/socket.io.js"></script>
<script src="http://code.jquery.com/jquery-latest.js"></script>
<script src="http://jashkenas.github.com/coffee-script/extras/coffee-script.js"></script>

<script type="text/coffeescript">
#...
</script>
</head>
<body id="socket.io.demo" onload="">
<h1>Socket.IO chat demo</h1>
<input type="text" autofocus="autofocus"></input>
<button type="button">publish</button>
<button type="button">broadcast</button>
<p>Status: <span id="status">Undefined</span></p>
</body>
</html>

client code
<!DOCTYPE html>
<html>
<head>

#...
</script>
</head>
<h1>Socket.IO chat demo</h1>
websockets
via socket.io.js
<button type="button">publish</button>
</body>
</html>

client code
<!DOCTYPE html>
<html>
<head>

#...
</script>
</head>
write
<h1>Socket.IO chat demo</h1> coffee-script
<button type="button">publish</button> in client
</body>
</html>

Lets handle
jQuery ($) -> the messaging
$status = $ '#status'
socket = io.connect()

socket.on 'connect', ->
$status.text 'Connected'

socket.on 'disconnect', ->
$status.text 'Disconnected'

socket.on 'reconnecting', (seconds) ->
$status.text "Reconnecting in #{seconds} seconds"

socket.on 'reconnect', ->
$status.text 'Reconnected'

socket.on 'reconnect_failed', ->
$status.text 'Failed to reconnect'

socket.on 'message', (message) ->
$('<li>').text(message).appendTo $('#messages')

$input = $ 'input'

$('button').click ->
socket.emit $(this).text(), $input.val()
$input.val('').focus()

</script>

Lets handle
jQuery ($) -> the messaging
$status = $ '#status'
socket = io.connect()

socket.on 'connect', ->
$status.text 'Connected'

socket.on 'disconnect', ->
$status.text 'Disconnected'
connection socket.on 'reconnecting', (seconds) ->
status $status.text "Reconnecting in #{seconds} seconds"

events socket.on 'reconnect', ->
$status.text 'Reconnected'

socket.on 'reconnect_failed', ->
$status.text 'Failed to reconnect'

socket.on 'message', (message) ->
$('<li>').text(message).appendTo $('#messages')

$input = $ 'input'


</script>

Emit events based on
client input

$input = $ 'input'


Lets add “Geo”
<script src=
"http://jashkenas.github.com/coffee-script/extras/coffee-script.js">
</script>

map = new L.Map("map")

cloudmadeUrl =
"http://{s}.tile.cloudmade.com/API-KEY/997/256/{z}/{x}/{y}.png"

cloudmade = new L.TileLayer(cloudmadeUrl, { maxZoom: 18 })

town = new L.LatLng(52.52267, 13.41293)

map.setView(town, 13).addLayer(cloudmade)

add HTML5 side
note

GeoLocation
get_location = ->
navigator.geolocation.getCurrentPosition(show_map)

show_map = (position) ->
latitude = position.coords.latitude
longitude = position.coords.longitude
markerLocation = new L.LatLng(latitude, longitude)
marker = new L.Marker(markerLocation)
map.addLayer(marker)
map.setView(markerLocation, 16)

get_location()

Add form for new user
<script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?sensor=false"></script>

geocoder = new google.maps.Geocoder()

$("#dialog").dialog({
autoOpen: false
buttons:
"Add User": () ->
geocoder.geocode { 'address': $( "#location" ).val() }, (results, status) ->
if (status == google.maps.GeocoderStatus.OK)
lat = results[0].geometry.location.lat()
lng = results[0].geometry.location.lng()
markerLocation = new L.LatLng(lat, lng)
socket.emit 'addUser',
"name": $( "#name" ).val()
"location": $( "#location" ).val()
"lat": lat
"lng": lng
else
alert("Geocode was not successful for the following reason: " + status)
$( this ).dialog( "close" )
"Cancel": () ->
})


<button id="create-user">Create new user</button>

<div id="dialog" title="Create new user">
<p class="validateTips">All form fields are required.</p>

<form>
<fieldset>
<label for="name">Name</label>
<input type="text" name="name" id="name" />
<label for="location">Location</label>
<input type="text" name="location" id="location" value="" />
</fieldset>
</form>
</div>

{
"name": "addUser",
"args": [{
"name": "Kashif",
"email": "kashif.rasul@gmail.com",
"location": "Torstraße 104, Berlin, Germany",
"lat": 52.52959,
"lng": 13.403620000000046
}]
}

Persisting your data in SpacialDB

Create a PostGIS
database in the cloud
➜ spacialdb create

{
"name": "spacialdb1_shoaib_burq",
"port": 9999,
"username": "shoaib_burq",
"host": "beta.spacialdb.com",
"password": "1436c20eca"
}

List your databases
➜ spacialdb list

[
{
"password": "1436c20eca",
"name": "heroku_shoaib_burq_dac1",
"connection_string":
"postgres://shoaib_burq:1436c20eca@beta.spacialdb.com:9999/heroku_shoaib_burq_dac1",
"port": 9999
},
{
"password": "1436c20eca",
"name": "spacialdb1_shoaib_burq",
"connection_string":
"postgres://shoaib_burq:1436c20eca@beta.spacialdb.com:9999/spacialdb1_shoaib_burq",
"port": 9999
}
]

Lets create a ‘Layer’ &
an ‘API’
➜ spacialdb layers:add characters --db spacialdb1_shoaib_burq

{
"name": "characters",
"srid": 4326,
"database": "spacialdb1_shoaib_burq",
"table_name": "characters",
"user": "shoaib_burq",
"api_url":
"https://api.spacialdb.com/1/users/shoaib_burq/layers/characters",
"acl": {
"get": "37f9e107e4a112eddcdc1c31fd12832a",
"delete": "1b62758e5e2948e6ef0cd0930516e5c7",
"post": "f0698e2664c04e2fe03702f07392e878",
"put": "7378dcc7eb8f628ffc702d5d27c8c7db"
}
}

List your API layers
➜ spacialdb layers

[
{
"name": "characters",
"srid": 4326,
"database": "spacialdb1_shoaib_burq",
"table_name": "characters",
"user": "shoaib_burq",
"api_url":
"https://api.spacialdb.com/1/users/shoaib_burq/layers/characters",
"acl": {
"get": "37f9e107e4a112eddcdc1c31fd12832a",
"delete": "1b62758e5e2948e6ef0cd0930516e5c7",
"post": "f0698e2664c04e2fe03702f07392e878",
"put": "7378dcc7eb8f628ffc702d5d27c8c7db"
}
]

# post the data to SpacialDB and
input =
geometry: { type: "Point", coordinates: [message.lng, message.lat]}
properties: { name : message.name, location: message.location }
post_url = "https://.../layers/characters?key=#{lyr_conf.acl.post}"
req =
method: "POST", uri: post_url, body: JSON.stringify(input)
headers: { "Content-Type": "application/json" }

request req, (error, response, body) ->
if error
console.log error
else
# then broadcast it
rec = JSON.parse(body)
get_url = "https://.../layers/characters/#{rec.id}?key=#{lyr_conf.acl.get}"
req =
method: "GET", uri: get_url
headers: {"Content-Type": "application/json"}
if error
console.log error
else
socket.emit('newUser', body)

# post the data to SpacialDB and
input =
geometry: { type: "Point", coordinates: [message.lng, message.lat]}
properties: { name : message.name, location: message.location }
post_url = "https://.../layers/characters?key=#{lyr_conf.acl.post}"
req = {
method: "POST", uri: post_url, body: JSON.stringify(input)
"type": "Feature",
"geometry": {
headers: { "Content-Type": "application/json" }
"type": "Point",
"coordinates": [13.4113, 52.5234]
request req, (error, response, body) -> },
if error "properties": {
console.log error "name": "Shoaib",
else "location": "Berlin, Germany"
},
# then broadcast it "id": 19
rec = JSON.parse(body) }
get_url = "https://.../layers/characters/#{rec.id}?key=#{lyr_conf.acl.get}"
req =
method: "GET", uri: get_url
headers: {"Content-Type": "application/json"}
if error
console.log error
else
socket.emit('newUser', body) # <== emits GeoJSON with the event

socket.on 'newUser', (message) ->
geojsonObj = JSON.parse(message)
users.concat geojsonObj
circleLocation = new L.LatLng(geojsonObj.geometry.coordinates[1],
geojsonObj.geometry.coordinates[0])

circleOptions = {color: '#f03', opacity: 0.7}
userLayer = new L.Circle(circleLocation, 500, circleOptions)
userLayer.bindPopup(JSON.stringify(geojsonObj.properties))
map.setView(circleLocation, 15).addLayer(userLayer)

Some exercises

• Real-world role-playing
games

• Disaster response apps

• Location based social
networking

Deployment

• Server with port 22 (ssh) and 80 (http)
• Capistrano deployment tool
• Bluepill, God, Supervisord, Monit, Upstart,
etc. process management tool

➜ cat Capfile
load 'deploy' if respond_to?(:namespace) # cap2 differentiator
load 'config/deploy' # remove this line to skip loading any of the default tasks

➜ cat config/deploy.rb
...
set :use_sudo, true

set :bluepill, '/var/lib/gems/1.8/bin/bluepill'

namespace :deploy do
task :start, :roles => :app, :except => { :no_release => true } do
run "#{try_sudo :as => 'root'} #{bluepill} start #{application}"
end

...

task :create_deploy_to_with_sudo, :roles => :app do
run "#{try_sudo :as => 'root'} mkdir -p #{deploy_to}"
end

task :npm_install, :roles => :app, :except => { :no_release => true } do
run "cd #{release_path} && npm install"
end
end

before 'deploy:setup', 'deploy:create_deploy_to_with_sudo'
after 'deploy:finalize_update', 'deploy:npm_install'
...

➜ cap deploy

➜ cat nodeapp.pill
Bluepill.application("app") do |app|
app.process("node") do |process|
process.working_dir = "/var/www/node/current"
process.start_command = "/usr/bin/env NODE_ENV=production app_port=80 node server.js"
process.pid_file = "/var/www/node/shared/pids/node.pid"
process.stdout = process.stderr = "/var/www/node/shared/log/node.log"
process.daemonize = true

process.start_grace_time = 10.seconds
process.stop_grace_time = 10.seconds
process.restart_grace_time = 20.seconds

process.checks :cpu_usage, :every => 10.seconds, :below => 5, :times => 3
process.checks :mem_usage, :every => 10.seconds, :below => 100.megabytes, :times => [3,5]
end
end

➜ bluepill load nodeapp.pill

Deploy to Heroku
➜ cat .gitignore
node_modules

➜ git init
➜ git add .
➜ git commit -m "init"

➜ heroku create --stack cedar
Creating sharp-rain-871... done, stack is cedar
http://sharp-rain-871.herokuapp.com/ | git@heroku.com:sharp-rain-871.git
Git remote heroku added

➜ git push heroku master
...

➜ heroku ps:scale web=1
Scaling web processes... done, now running 1

HTML5 Mobile

iOS Android Blackberry IE Opera Firefox webOS Symbian

Geolocation ✓ ✓ ✓ ✓ ✓ ✓ ✓
Web Sockets ✓4.2+ ✓6.1+ ✓ ✓
Web Workers ✓6.0+ ✓ ✓
Web SQL
✓ ✓2.0+ ✓6.0+ ✓ ✓
Store

Live Demo:
geochatapp.herokuapp.com

Async. and Realtime Geo Applications with Node.js

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